All Wheel Drive Auto: Independent Seattle Subaru Service


Your Subaru Check Engine Light Explained

The Check Engine Light explained

Starting in 1996 all passenger vehicles and light duty trucks produced or imported for sale in the U.S. had to be OBD II compliant (On Board Diagnostics two). As well as meet newer vehicle emissions regulations. Part of this technology involves the check engine light or MIL. (Malfunction Indicator Lamp). While it’s true that prior to 1996 the check engine light did exist on vehicles, it took on an entirely new meaning and purpose in 1996.And this is where the confusion starts.

The check engine light comes on when the ECM (Engine Control Module) recognizes a malfunction with an emissions control device or an emissions control device monitoring system or if a specific condition is not being met. In many cases the vehicles overall performance won’t change much if at all when the light comes on, and is thus not taken seriously by the majority of car owners. But what the light represents is a potential failure in one or more of the vehicles systems that are meant to control the level of tail pipe and evaporative emissions produced to acceptable levels. In some cases the light can come on when the gas cap is loose. But the light can also come on when the catalyst system has failed.

Normally neither one will adversely affect the vehicles performance but both will allow the vehicle to excessively pollute our environment. The gas cap is meant to keep the fuel vapors sealed in the tank and evaporative emissions system rather then allowing the fuel vapors to enter the atmosphere as hydrocarbon emissions. The catalyst system is designed to lower tail pipe emissions to acceptable levels. These are just two examples of many possibilities.

There are essentially two types of OBD II Fault codes, conditional and component. A component code usually indicates a problem with a particular device, its circuitry or controls. A conditional code is set when a specific condition triggers the ECM to Command on the check engine light. Conditional codes are the hardest to accurately diagnose and repair and are typically the ones that do the environment the most harm. It is almost impossible to accurately diagnose and repair a conditional code with a code reader from a local parts house. It is simply not enough to have the code number but rather a thorough analysis must be performed by a qualified professional technician.

When a code is cleared, the emissions systems monitors are also turned to not ready status. It takes a specific drive cycle to return the monitoring systems back to ready status and the whole time the monitors are off they are not monitoring the emissions control devices. This is why sometimes a code can be cleared and not come back for weeks. Until the monitoring system is back to ready status the ECM doesn’t know about a device or a condition.

Specializing in Subaru repair gives us an advantage over other general repair shops when it comes to the diagnoses and repair of the check engine light and vehicle emissions systems on your Subaru. We will accurately diagnose the failure, any potential causes of the failure and keep you informed the whole way through. More importantly we can provide you with tips to help reduce the amount of emissions your vehicle emits and keep you an informed Subaru owner.

The above was prepared and written by.

Justin Stobb

Owner All Wheel Drive Auto

ASE Master Certified Technician, L1 Advanced Engine Performance Certified

WA. State Dept. Of Ecology Authorized Emissions Specialist

Share on facebook
Share on twitter

753 Responses

  1. I live in Crestline California and our community has a large amount of Subaru Outbacks on the road. Everyone that I know that has a 2000 has their check engine light on. We have had the codes checked and random issues that are not resolved even with replacing parts. When 6-10 people experience there is a design flaw.

  2. Craig,

    Please remember I am unbiased and only trying to factually educate you and other readers.

    A check engine light can come on because the driver puts gas in the car and did not tighten the gas cap up. How is this design flaw? It is mandated by law by the Department of ecology.

    The check engine light is geared towards alerting the driver when the computer sees a problem with the vehicles emissions system and there are Thousands of possible reasons for the light to come on.

    Just as there are a thousand reasons you might have a headache but bottom line the only thing you know is that you have a headache or a check engine light is on. If taking aspirin doesn’t fix your headache is your body a design flaw? Or was your headache not diagnosed properly or maybe there are a number of things contributing to your headache as your whole body is aging at the same rate of speed. Just like every part in your car is the same age and guess what, things are going to fail in unison.

    If a check engine light comes on and a code number P0325 Knock sensor circuit is set, and then diagnosed by a pro, not a code scanner at your local parts store, the P0325 should be satisfied once the properly diagnosed condition is repaired causing the code P0 325. If the check engine light comes back on a week later and now its P0440 Evaporative emissions system leak detected that is a new problem that must be diagnosed by a pro, it may be the gas cap is loose but it may also be that the purge canister has a leak also.

    Due to how the emissions system works not every system is monitored by the vehicles computer every second the engine is running but rather when a specific event is met. You can look online for an OBDII drive cycle and see what I mean. You can ATTEMPT to fix a problem but it may be weeks or months before the computer actually has the proper monitor turned back on to ready status. Until the monitor is ready the computer does not have the ability to command on a check engine light based on a failed component or condition triggering a code.

    Typical problems with the 2000 Subaru Outback that will trigger a check engine light are a failed knock sensor, failed Catalyst system, failed front air fuel sensor, failed rear 02 sensor, loose gas cap.

    Every one of these items fails just as often on any other Japanese import as they are almost all made by the same vendor first of all and subject to like environments in which they can become damaged.

    If a check engine light is diagnosed and comes back on for the same reason aka a reoccurring PO325 then the diagnoses was wrong or incomplete. If the light comes back on and it is a different code it’s a different problem.

    The real problem is that the parts stores try to devalue the real skill and knowledge it takes to truly diagnose a car, as does franchised auto repair shops such as the Tune and Tire centers.

    If you take your Subaru to a Independent Subaru expert and your neighbors and friends alike the experience will be different or hopefully after reading this you may better understand it’s a complicated process sometimes not a design flaw.

    Do also remember that the goal is to try and clean up the environment.

    If you are driving your Subaru around with a check engine light on you may not be doing your part to help

    1. Thank you for your answer, I am a mechanic myself and sometimes im up late at night watching a infomercial tell everyone all you have to do is buy my docMD and it will save you thousands on repairs and keep crooked mechanics from riping you off. It makes me sick to watch that because I spent 40,000 on a education teaching me how to properly repair. Just because you can read a code does not mean you know how to fix the problem their are so many systems with so many different functions. Repairing one thing might have just been the cause of another problem, but how is one to know unless you are properly trained. everyone thinks its easy, ya well let them try. Good Luck. Any ways you tell the truth and I thank you for that.

      1. here is one for the record we have a 1997 outback 2.5 the check engine light works but does not come on, but when I took it to get smoged the code entered for check engine light and still no CEL they all say thats weird and thats as far as we get?????

        1. Um there would have to be a code number, that’s the way it works. If the scanner is picking up the CEL is commanded on but there is no code or no light the first step is to replace the ECM.


          1. Hi Dawn,

            Pre 1996, it takes the Subaru specific Scan tool to get into the ECM and obtain codes and the data needed to diagnose your Legacy. Without the codes and appropriate data the light tells us one thing, and that is there is a problem that needs to be diagnosed.

            Sorry I cant offer more


        2. Heh. On my old Ford Ranger, I spent beaucoup bucks keeping that light off. After about 250K miles, things started to go and I pretty much gave up, driving that thing around with the check engine light on and only having it fixed at smog time.

          Finally, it stayed off for for the whole two years between smog checks and I was quite pleased about that at the next smog check… well, it failed anyway b/c there was a code. The light was off because the bulb had burned out! Oh, well. That was another $150 to change the bulb. Well, the bulb was only 50 cents but the labor to pull the whole dashboard out to get at it kinda ran the bill up 🙂

          After 390K miles the engine finally gave out so I bought my Outback. This blog has been very helpful!

      2. I have Subaru Legacy 2001 model, auto, non turbo EJ20 engine. The vehicle has a check engine light on and every morning when i start the engine, I cannot accelerate immediately until after a minimum of 50 metres. We have changed the airflow sensor but the engine light is still on and the vehicle hesitates to accelerate in the morning. Regards

        1. Hi Cleverly,

          Like I keep trying to reiterate in the comments section here, If you want any help at all with a check engine light, you must have the code number..

          The light is merely an indication that the car needs to be diagnosed, and that’s all I can tell you with only the information being that the light is on.

          I am sorry but that’s just the truth of it.


          1. I have a 1995 subaru liberty /legacy it shuts of on the highway at 100klm like looses all power if I turn key off and on wile rolling will start going again after gets up to operating temp if u turn of then try start it the cheak engin light comes on and u carnt accelerate at all for about 20 seconds or it will die iv had this problem now for 6 months carnt fix it and no mechanic can tell me what’s wrong and now my fule Guage has started playing up any suggestions

          2. Hello Rowan,

            There is a lot of possibilities. Its difficult to really offer help from afar. The older 2.2l could suffer from sticky valves and a lot of techs could not get to the bottom of the symptoms. Knowing the code that is set when the Check Engine light is coming on would be helpful. Ive seen alternators cause all sorts of problems in older Subaru’s as well.

            I am sorry but there just isn’t much I can offer without seeing the car.


    2. my check engine light came on… and i also have a flashing cruise control light. the car is a 2005 legacy. the cruise is not functional since that light started blinking.

      1. I have exactly the same situation in my ’07 Outback 2.5 4 cyl…
        The car runs fine, and all the fluids are full…
        My daughter who is a Ford service advisor agrees that it’s no big thing, except the cruise won’t work on mt 800 mil;e trip home later this week…;-(

      2. So did they tell you why this is happening, cuz it’s happening to us as well, check engine light is on and cruise control light is flashing and won’t go off or work????????? Ours is 2008 Subaru Outback

        1. Yes, my ’05 Outback LL Bean 6cyl is doing this – CEL, ABS light both came on w/ flashing cruise control light & “Er55” showing on trip odometer & cruise not working – does anybody know what is going on???

          1. The cruise control light is flashing because it has been disabled by the check engine. When the check engine comes on it disengages the cruise control to avoid both accidents/malfunctions during motion and to keep you from overriding the system.

      3. I have a ’05 Subaru (which I love) and have experienced that problem a few times. I’m not a mechanic, but have observed this enough times to notice the following: any time the cruise control is stressed (a lot of uphill/downhill driving, sudden stop/go traffic in freeway, forgetting to shut off cruise control after leaving highway conditions, etc.) the transmission shifting (into sport? overdrive?) seems to create an emissions problem of some sort. The check engine light comes on, the cruise control indicator flashes and cruise control does not work. Usually I have to start up and drive the car for two days, and all the lights magically go off, and the cruise control works again.

        I think of it as cruise control abuse on my part, and have learned to avoid it!

    3. My check engine light just came on in my 2002 Subaru Outback Sport… I live in Hawaii and my Outback has a salvaged title. i dont know much about the history of the vehicle, but it does make a kind of clicking noise when I start to speed up. I noticed a lot of the comments have to do with a 2000… I was hoping you could tell me the typical reasons the chek engine light would come on for this year/model. I’ve notice that its been idling different when stopped in traffic, like it might die out. It hasn’t had any problems since I bought it in February, but it is overdue for an oil change. Any advice you can offer me so I can seem semi-educated when I take it in to be services would be greatly appreciated. If you can recommend a great Subaru mechanic in Honolulu, Hawaii- that would be even better! I am a mother of 3 young children and this is my only car! I just started a new job this week and public transportation is not an option for us! Please contact me if you can offer any helpful insight.

      Thank you!!!

      1. Hello Vel,

        In order to try and help you I need you to go get the codes scanned, there are a couple places on Oahu that will do this for free. I wish I could remember the name of the road, but its on the way to the Stadium that has the swap meet coming from the Ko olina area. When we were there last year I took a friends car to a parts store to get a code scanned so I could help figure it out for her.

        If you can come back with a code number I can try and point out a scenario for you, but with out the code numbers there are way to many possibilities. The number one reason is a loose gas cap.

        I know of no one in Honolulu to recommend to you or any where on the island actually, sorry.

        If you can get it scanned ill try to help.


        P.S. if you buy a code scanner you can get the code your self.

        Here is a link

    4. I have a 95 Subaru Legasy Wagon, AWD. it was throwing the code for the knock sensor. I replaced it and now there are no codes. however the CEL is still on. any Ideas on how to clear it or fix a non reported by the ECU problem?

      1. Hello Steven,

        Typically the light can be cleared with a code scanner on the 1995 which was pre OBD but did in fact have the same connector. I have always had the factory tool so I am not sure if a basic scan toll will work on a 1995, you could also leave the battery disconnected overnight.


  3. Dear Justin,
    Thank you for your informative response. We own a 2001 Subaru Outback Limited and live in Central California. The “check engine light” went on the first time we drove the car after a month’s vacation (sans Subaru). Unfortunately, I need to have a smog check for registration purposes. The smog check people told me the car would fail the smog check with the check engine light on and that they would “diagnose” the problem for $80, in addition to the $40+ charge for the smog check. After reading your article, it seemed to me that for $80, the smog checkers would just disable the monitoring system, run and pass the smog check, but not “fix” or accurately diagnose the problem. I originally bought the car in Washington State and we are driving back up there this week. After buying gas and tightening the gas cap (do I need to reset anything?), I am thinking of driving up to Washington to have the car looked at. We have a good, honest mechanic up there. What is your advice? Thank you.

    1. I live in CA, and had a Ford with very active check engine light 🙁 so I’m pretty familiar with the rules.

      The shop can reset the light, but you can’t get it smogged right away – the wire they plug at at the smog center will show that the sensors have not reset and you won’t pass. You have to drive around for a few days (and approx. 75 miles or so depending on the car) for all the sensors to re-activate. That’s why the light will often come back on a couple days after the codes are “cleared” at the shop or by the guy at the auto parts store. The smog check machine has to see that all the sensors are active.

      It didn’t used to be that way – some years ago you could just clear the code and get the smog check before the light came back on, but the California BAR (Bureau of Auto Repair) changed that. All sensors have to be reset and active now, so you have to drive for a few days between the repair and the test.

      Ask the smog guy to check the sensors first before he runs the test. For some stupid reason, they’ll run the whole test and then fail your car because of that, probably to get the money. Tell them to check the sensors first, and tell you if they are all “ready.” If not, go drive the car some more and bring it back another day.

      But anyway, they won’t disable the system to get the vehicle to pass. Well, some will, but it will cost you $300 or so…

      1. Hi James,

        So to help explain. When the light is cleared what is actually done is the short term memory is erased which also takes all of the critical emission system monitors and turns them to not ready status. For each monitoring system there are a sequence of events that must first be done in order to turn the monitors back to ready status.

        In order for a car to be tested the majority of the monitors must be ready. If they are not ready it’s an automatic fail.

        Yes if the monitor that watches the front air fuel ratio sensor is not active the computer will not know if it’s working or not for example and would be able to report that its not with a check engine light.

        The rules did change and in the State of Washington they do not test cars that do not have all of the monitors at ready status, or depending on what year one or two may be able to be at not ready status and still take and potentially pass the test.


  4. Hi Ellen,

    So the monitors have to be on to pass the emissions test in Washington state as the car is tested at test station and not at a shop.

    I cant really speak as to what the smog station in California would be testing or just how good their analysis would be

    If the check engine light comes on and sets p0440 evaporative emissions system leak and the gas cap is found to be loose, tightening up the cap and a few drive cycles with the(ECM) Engine Control Module seeing no failure to pass the test the ECM will turn the light off.

    A flashing check engine light means stop driving the car, a check engine light on steady, means proceed with caution.

    It is hard to tell you if you should drive it from there to here with the light on or not. The code number at a minimum would be a good starting point to know how to best advise you.

    Most parts houses will offer to connect a generic OBD II scan tool up to your car and tell you what code is set for free. Maybe start there, drop me a line when you get the code and we can go from there.


  5. My check engine light on my 1996 Subaru Legacy Brighton recently came on and stayed on. I took the car to my local mechanic who ran the obd 2 scan tool. The code came back as a number 4 cylinder misfire. My mech called me and advised to start by replacing the plug wires. I went to the mech shop to pick up my veh after hours as shop had already closed. Once I started the vehicle my check engine light now flashes ocnstantly and will not stop. I have checked all of the fuses that I can find and all appear to be ok and have unhooked and rehooked the battery to reset the light. I went ahead and replaced the plug wires as directed but no change. Will note that the cooling fans run with the key turned “on” but not started and can hear the fan relay clicking. Once the veh is started the fans turn off until veh heats up. I have not noticed any problems with running the veh or any missing. The only problem now seems to be with the constantly flashing check engine light. I have searched all avail websites and can not find any useful info. Please help if you have any idea what could cause this to occur. Thanks.

    1. You have the green mechanical “test” plug connected. Normally it should not be connected. The green color connection plug is used by mechanics to test the system. If you disconnect the green connection under your steering column it should resolve itself. Good luck.

      1. John, Thank you for the answer. It greatly helped me. I purchase a non running 98 outback from a lady that was molested by a back yard mechanic. I don’t know if he plugged in the green plug or I did in the process of troubleshooting the problems.

        Anyways, when I got the car running the check engine light was flashing but had no codes, I was like WTF. Your post saved me a lot of time, thanks!

      2. Thanks Jon,
        I saw a few disconnected plugs under there below the steering column in my 1998 Legacy while trying to get my AWD driving the rear wheels. I guess I shouldn’t have re-connected them, but after about 30 hours on the problem I was getting desperate.

        Next thing a Check engine light flashing on the dash… I disconnected the yellow/green plug but that got me another warning – Airbag. Not that one then. I seem to remember finding a green one somewhere, possibly behind the stereo? Was it a single wire?

        By the way is there anywhere here where someone has figured out how to get the rear transmission to work/drive?


  6. by the way, i kept reading the q and a’s and found that the green “d-check” plug was hooked up. the shop is closed today so i can not ask them if they hooked it up or not to run the obd 2 scanner. once the plug was unhooked, the ce light stopped flashing. even though i have not received a reply i can say that this site truly helped. thanks.

    1. Hi Justin, 01 sub outback ( Legacy ) h6 3.0. PO171
      cyl #1 denotes bank 1 (definition) 4 causes by autozone scanner. lean code. I know I need to get ckecked, no sub dealer close. Hi miles 275,000 just had trans flushed, fixed diff post “donuts/grommets”. Car runs ok for high miles. in cruise, steep hill rpm jumps to 4,000, sometimes doesn’t disengage and stays until manually take out of cruise. Goes back to 2,700 rpm. Can this have anything to do with code ? also VDC light comes on bout same time check engine light comes on. Any advice ?

      1. Hi Larry,

        The best place to start is with a fuel pressure test, that’s one of many tests that may be needed, but the most logical place to start and a common issue with the H6 both for fuel pumps and regulator.

        Hope that helps


        1. I just bought an 03 Outback H6 a month ago, it’s been driving fine, and still does, but 2 days ago the Engine light and VDC light came on simultaneously, I plugged in an OBD harness which came up with 7 Transmission codes and when I cleared them they came straight back. I also noticed the stored memory plug was connected, I don’t know how long this has been the case as I’ve only just got the car. I’ve checked all the wiring plugs for corrosion and cleaned all the earth points that I can find. When I clear the codes they come straight back. Also if I plug in the green diagnostic plug the engine light just continuously flashes quickly, and the
          engine fan cuts in and out, but there is no pause in the light flashing at all. Where do I go from here?

          1. Hello Marcus,

            You would start by diagnosing the codes set in the TCM, you would also not want to leave the green “D Check” connector connected its for diagnostic purposes only and yes the check engine light will flash, all solenoids will click and the cooling fans will cycle with the green connector plugged in.

            You need to stop clearing the codes as you also wipe out valuable data needed to diagnose the issue.

            You can buy a Service manual or use online resources such as All Data to print out diagnostic flow charts and then trouble shoot.

            Hope that helps


        2. Hello Justin
          I have a 01 Outback Limited and has 140,000 miles it was running smooth until about a month ago..
          The signal light sound came on and will not stop clicking but signal all work so does hazard lights.Then the car would not catch speed when you would put it on drive it would hesitate then it would catch its speed..Check engine light came on and code was P0303 so changed spark plugs and wires and car was still acting the same way so replaced Ignition coil and nothing, he will start rough and drive with a struggle can have gas pedal down and it does not accelerate and the RPM is high…now we have 10 different codes P0340, P0303, P1110, P1112, P0107, P0112, P0113, P0111, P0032, P0031 it went from 1 Code to 10 Codes…..Please any advice would be greatly appreciated

          1. Hi Priscilla,

            Sounds like you had a improperly diagnosed cylinder # 3 misfire code and in the course of throwing parts at it more problems have emerged.

            Best place to start is Diagnosing the misfire, this would include a compression and leak down test, physical examination of the valve guides, a test of the fuel injector and wiring, as well as evaluating the ECM.

            From there the stuff that was done needs to be looked at as its possible some of the parts you put in are in wrong or poor quality.

            That’s what must be done to get to the bottom of it.


          2. When you replaced a whole bunch of parts, specifically the ignition coil, did the ground located to the top left of the coil(bolted to the intake manifold), get removed or loosened for any reason? I’ve seen that ground get taken off and not put back on properly and it caused a bunch of similar codes because the sensors no longer had their ground to return.

    2. Justin,

      I have check many blogs on the internet and this one seems to be very knowledgeable about Subaru. I have been having a major issue with my 1998 Legacy Outback. I now have no dash lights, the check engine light is on, no horn, no emergency flashers and I am over heating because it seems the cooling fans are not coming on. I am not the best at cars. It seems to me that this is more of an electrical problem. Any words of wisdom would be very helpful.
      Thank you.

      1. Hello Barry,

        Thats not fun! From here I am only guessing, but would suspect a portion of the primary wiring harness to the main fuse block under hood or secondary under dash has melted and is shorting out.

        Need to start with checking fuses, than checking for power loss. Cant be driven any more needs to be parked until repaired.


  7. i have a subaru legacy GL 2.0 1999 ….
    which shows the check engine for the 1st time
    checked it and says
    22 Knock sensor
    so i went to the dealer and buyed it for 50$
    replaced it and start the engine but the check engine ligth is still there w8in for me….
    i checked it agine and it sayes
    22 Knock sensor
    which is replaced the same day !!!!!!!!!!!!!
    what can i do to remove this check engine light???
    help 911 !!!!!!
    plz need a help soon

    1. It’s bought not buyed and waiting not w8in…
      Secondly, you have to reset the code before the check engine light will turn off………..

  8. Hi, I have a Subaru legacy GT 2.0 2001 which has been showing the check engine light for a while now. Sometimes when I brake or accelerate it goes off but will come back later when I restart the car. My front brake pads were worn out but I replaced them, now my left brake bulb is not lighting could this be the reason for the check engine light coming on?

  9. I have a 2006 Subaru Impreza Outback Sport with 40000 miles. After a drive on the highway today (about 140 miles round trip) my car started to shake when idling. I assumed it was because fuel was low and was on the way to get gas anyway. After filling the tank, the stutter when idling continued and thecheck engine light began to flash. When I turned the ignition off, the vehicle had a strong burning rubber smell. Any thought on whether it is safe to drive to the dealership at this point to have it checked out and whether this is something covered under warrantee?

  10. Hey Erica,

    You have a misfire and you really should have it repaired, a flashing check engine really does mean to stop driving the car. You can do damage by driving it to far and too long with a cylinder misfire.

    Most likely it is a failed ignition wire or spark plug neither are still under warranty, there are of course other possibilities and I am really only advising you on the most typical things we see.


    1. Hello,
      My subaru legacy 2001 has check engine light on for sometime now.But what surprise me is that the check engine light goes off when the car is washed or when it is raining. Anyone with an idea of what could be causing this, can help or is it because the aircone stopped working on this car because the earthing for the same was not transmitting to the main fuse box.

      1. Wow… Finally, I’ve found a post like the problem I’m having… I know it sounds crazy, but my 01 Jaguar s-type check engine light stays on, but goes off when its raining or very humid outside. If you have a fix for this, Please Post…


  11. I have a subaru Legacy Brighton 2000,and of course the CEL is on .Since I can smell exhaust inside the car.
    I am going to buy a scanner ,could you tell me where to plug it in?.Also just for info, after 160000 miles the clutch is the original one.Thank you for your time.

  12. I have a code P0420. Do I replace the sensors first or just bite the bullet and replace the catalytic convertor? If replacing the cat is it Okay to replace with a universal catalytic convertor which is far cheaper or buy the OE one? Any ideas would be greatly appreciated.

    1. My 2001 Subaru Forrester is reading code P0420. We have replaced the two OT sensors and the catalytic converter. It is still sputtering, backfiring, and what seems to be not enough power. The check engine light will not go off and it is flashing at times.

      1. Hello Stephanie,

        The P0420 code points to a non proper functioning catalytic convertor or sensor issue. This only has to do with monitoring the oxygen levels in the exhaust system based on the fuel trim and expected levels after changes. A Catalytic convertor issue is not causing the Subaru to run poorly but if the car is running poorly and not addressed it will ruin the Catalytic convertor.

        The flashing check engine light is telling you there is s cylinder misfire, and the same thing that is setting the flashing check engine light is what is causing the Subaru to run poorly.

        The code scanner you are using must not be displaying all of the codes or is broken Start with a different code scanner from there have it diagnosed if you are unable to do so.


  13. Hey Keerthy

    I would test the sensors and if they are slow to respond to forced mixture changes I would start there. I would also try to increase the exhaust temperature for a while afterwards to try and burn out any contaminants in the catalyst.

    The aftermarket cats seem to last just about one year they are cheaper only as a result of having less precious metal in them which affects the performance and longevity.


  14. Thanks Justin. I dont know if its okay to post the question in this thread but here goes.

    My 97 Legacy Brighton MT is in the shop to replace the clutch and has 192K miles. Recently acquired and I have no service history, what are the things you suggest changed at this point?

    It is a 2.2L H4. Steered clear of the 2.5 because of the headgasket issues.

    I came across this website after the car went to the shop else I would have brought it to you since I live in redmond.

    Will come by for an inspection after I get the car back from the shop as I live in redmond.

    P.S : Please feel free to move the post if it is inappropriate here.

  15. I had a problem with my CEL staying on for several months in my 2005 Subaru Outback, even after having a diagnostic test at a Subaru dealer and replacing the left fuel-air sensor which the test showed as weak. Solution in this case was simple: buy only gas that has no ethanol in it. Shell or Exxon has no ethanol in it. The boxer engine doesn’t burn hot enough to remove ethanol from the air/fuel and oxygen sensors, so the CEL goes on (and your cruise control goes off!). Since filling up with Shell my light has been off for good. It may take two or three tankfuls, but is sure works well!

    1. Kent;
      My CEL came on on the way to work today. For the first time I filled my tank with an off brand gasoline with ethanol instead of with Shell a few days ago. I also used some fuel injector cleaner. This makes since to me if ethanol can cause the problem. I will clear my codes and fill up with Shell from now on.

      1. Rather than clearing the code, I would first see whats set, it may be completely unrelated.

        The light can come on for many reasons some of which can leave you stranded if ignored.


    2. I had the same experience — drove across the country in my 2003 Impreza Outback (56k total miles on it), had put a couple of tanks of gas containing 10% Ethanol in there. . . and the CEL came on (for the first time ever). Upon arriving in L.A. I changed the oil and flushed the coolant. But then I saw this post and after 2 1/2 tanks of gas with no ethanol the light has switched itself off! Thank you for the advice. .

      1. Hello, I have an 09 Subaru Forester 2.5l turbo. I keep getting a flashing cruise control light with a constant check engine and traction control disabled light.
        Was told my code is a slightly over advanced timing and a bad catalyst code…. how can I fix the over timing code
        Also I’m get an average of 18mph….

        1. Hello Shane,

          To fix you would need to know the cause of the fault, then repair that fault and confirm the repair resolved it. In order to know the cause a proper diagnoses would need to be performed. There are just to many variables to begin to suggest a fix over my keyboard.

          Sorry I cant offer more.


    3. I actually discovered this myself.

      A few years back my Check Engine light came on. I took it to my mechanic and he goes “oh that error sucks, as we can’t pin point it, however 80% of the time it’s your gas cap”.

      Well I replaced the gas cap, and no luck. Now my mechanic also said he’s known people who drive the life of the car with this error and never have issues.

      So for about 2 years I drove with the light on, meaning to get it fixed eventually, but waiting as it could be costly cause my mechanic said “we just have to start from one end and work our way down, stopping once we fix it”.

      But about a few months ago I noticed my check engine light was off. I was shocked, I thought the bulb burnt out. But after getting one of those computer checks (name slips my mind), and sadly finally paying attention to my lights, I realized this wasn’t the case.

      So what changed? Well it took me a little while to figure out, but I realized, I stopped filling up at Conoco, and started using Shell (cheaper price). I have come to the finalization, this is the cause. And what makes them difference? Ethanol.

      Here’s something more interesting. When I fill up with Ethanol laced fuel, I can fill up my tank fuller, to the point where my needle sits about “F” for about 50 miles (I do my MPG after every tank, and have seen when I switch fuels this happens). For instance the Shell I filled at today had 10% Ethanol (was testing this last theory). I found my mileage drop by about 5 miles (I divide mileage since last tank by how much fuel I add).

      The last time a jump like that happened was when I switched from Conoco to Shell (that had no Ethanol or very little)

      1. Hello James,

        I have posted quite a bit about some of the older models ( pre 2010) and Ethanol.

        So its real possible that not using Ethanol may help.

        Not knowing the code however makes it impossible to determine if that’s realistic however.


  16. Hi,

    I have a 2002 Subaru Legacy. The CEL has been on for several months. Autozone told me the code is P0420. My husband looked under the hood last week and found that the coolant is completely dry in the reservoir. Dried up coolant had happened before, but I kept forgetting to check often.
    What can cause the coolant to be depleted? Is this related to the CEL and code P0420? Should I have the cat replaced?

    1. If you have a Subaru consuming coolant 99% of the time it in either an internal or external head gasket. If you fill up the radiator & the reservoir ; when you get the engine hot you should see bubbles in the reservoir ; that means it’s internal. If you get a sweet burning smell from the engine ; that means it’s external. Either way you need a head gasket job. 42 years experience.

      1. Hello Mike,

        There are a few things even with 42 years of experience you may be overlooking.

        1. Coolant can and will evaporate, having to top off the coolant in between oil changes is not something that automatically indicates there is a HG failure or even a leak somewhere.

        2. There are lots of other components on a Subaru or any other car that can and will leak, the single most common is the plastic tank to Aluminum Core seal on the modern era Radiator, I would hate for anyone to jump to the conclusion because they have an external coolant leak that its the Head gaskets when the single most common component we replace is the Radiator and generally after 8 to 10 years of service.

        3. Radiator tanks are also prone to cracking mostly during the Winter months as the aged tanks become brittle during the cold and then expand greatly as the coolant reaches operating temperature and this can cause the tank to crack, the most common place is the upper tank.

        4. The type of Hose clamps Subaru used in many applications up until the current era production needed to be tightened during periodic maintenance such as a 30 or 60k service, this is mostly omitted by most techs and as such the clamps become loose over time from daily expansion and contraction, the fix can be as simple as tightening the hose, but in some cases the hose may need to be replaced, the most common would be the Upper radiator to coolant cross over pipe connection.

        In closing not every Subaru will develop a Hg leak, not every Subaru will develop a coolant leak for that matter, but if coolant loss does become an issue the best way to go about it is to properly evaluate the situation prior to ever jumping to any conclusions or making assumptions. I would sincerely hope given your experience that would be your suggestion to your customers as well.

        Thanks for posting


  17. Hi Mel,

    One of the most common mis diagnosed codes is PO420 a code reader from Autozone is just that a code reader. The value in the diagnoses is the same as you have paid for it. Having the code only tells which code the computer is setting in connection with the light coming on.

    PO420 is set on every car when the computer does not see a significant increase in the oxygen levels in the exhaust as it travels through the catalyst. A properly functioning catalyst will convert some of the carbon monoxide created in the combustion process of the engine and convert it to oxygen.

    There are many things aside from the catalyst that can cause a catalyst code.

    My guess based on the coolant loss is an internal head gasket leak allowing some coolant into the combustion chamber and thus into the exhaust system.

    But I am not clear on how quickly does it loose coolant?

    The water in the coolant will evaporate and does need to be topped off at every oil change interval at a minimum.

    IF you want the right results I would seek out a good independent Subaru shop in your area and let them diagnose it locally rather then just replace parts without a real diagnoses.


    1. Hi – this was a very informative response. Had not been checking my coolant as i guess I was depending on the service oil change to do so. Anyway – the check engine light came on this morning on the way to work. The level looks a bit low. I would like to think “NOT” a head gasket leak as they were replaced in December by subaru with a compromise of cost as the gaskets on some of the 2002 models do leak. Don’y fully trust Subaru as the local dealer I purchased the car at stated that they did not have to tell me of the recall due to the fact that I was the second owner.
      I will also take it to be diagnosed.
      Have a nice day.

  18. Hi Justin,

    Thank you so much for your knowledgeable response. I wish I lived in Seattle so I could take my car to your shop. The local Subaru dealer here only wanted to replace the cat per PO420 code without any diagnostic tests. Thus, I have not been willing to let them do that.
    The first time the coolant went dry was November 2008.
    Today, the battery went dead and Walmart replaced it as well as the terminals.

  19. I have a 2001 Outback limited with about 95k miles. I had a CEL that was reading misfire in cylinders 3 & 4. I started with spark plugs. No change. I then did wires. Still no change. I switched out the ignition coil for 3/4. Things were good for about 10 days and now it is coming back on with only a misfire in #4. I am trying FI cleaner and Lucas oil fuel system treatment, hoping that a possible FI clog will be the cause. Any other ideas on what I should look at? The car runs smooth and I feel a VERY slight vibration when cold and at idle. Thanks!

  20. I was wondering if anyone might be able to help me. I have 98 impreza 2.5RS, and I am going through my yearly inspection in NY state. I have a code reader for my OBD2 and I am able to see the codes and erase them. My question is, how do I clear the incompletes from memory, after I erase the codes. I heard three driving cycles or 200 miles without setting the CEL off. If anyone knows exactly what a driving cycle consists of, or if my information is correct, please let me know! Thanks.

  21. Regarding “D-connector” or “D-check” plug and CEL:

    I recently bought a 2007 Subaru Outback. I noticed a green connector on the passenger side, under the glove compartment, just above where the floor carpet stops. Thinking it should be plugged in, I connected the two sides together. The CEL came on. To make a long story short, with the green plug connected, error codes P1518, P0851, P1152, P1153, and P0140 all showed up when I went to a local parts store and they hooked up a computer. I disconnected the green connector and the computer showed “pass” on everything/no error codes. I called local Subaru shop and they explained this green connector is called a “D-connector’ or “D-check” plug, and it is supposed to be DISCONNECTED. Apparently they have to connect it to do some kinds of tests in the shop, but otherwise it is supposed to be DISCONNECTED. Maybe everyone else already knows this, but it took me a lot of searching and anxiety to find this out, so I hope this information will be helpful to someone else.

    1. Hi Tony,

      I recently looked under my dash and saw the green connector disconnected. I connected it, thinking my local dealership forgot to connect it, as they have forgotten to do a few things over the years. The next time I started the car several days later, the CEL started blinking. I came to this forum to do some research, and in reading your and others postings, I realised the cause of the CEL blinking. I just went out and disconnected the green D-connector, and the CEL stopped blinking. It is on, but that is nothing new.

      Thanks for your post.


    2. Just had the same thing happen to me this weekend while troubleshooting a plugged evaporator drain. I saw the green harness unplugged, said “that can’t be right”, and ended up with CEL. I, too, called the dealer for confirmation after disconnecting it. Glad to have confirmation from another DIYer.

    3. You are the MAN!!!! Just by chance, the wheel well drain hose (for rain runoff) became clogged and saturated the passenger seat of my GF’s car. I was under there trying to see where the water came from and I thought I had inadvertently disconnected the ‘green plug’. I plugged it in…. today I hooked my diag unit to it and received codes P0140, 0851, 1152&53 and 1518 just as you did. Just read your post (coincidentally) and plugged in the green connector. All set now. THANK YOU!

    4. This was so much help, i do work in a shop and had a 2007 impreza come in and i saw the flashing CEL light and thought misfire. Connected solus and was reading all those codes, did all the tests and was just running men in circles. Got very frustrated with this car. Especially with all the relays and fans kicking on and off. Went and looked and that green plug was plugged up, disconnected it and solved all issues other than the starter that needs replacing.

  22. My engine light came on this afternoon. It was suggested that the gas cap might be the problem. When I checked it I discovered that it was not on tight. When I started the car the engine light was still on. I have been in a panic afraid to drive my car and afraid of how much I may have to spend to get it corrected.
    Your article gave me such a sense of peace and a good feeling that I can better describe my situation to the service department!
    Thank-you! I hate all this computer stuff in cars but I still ove my subaru!

  23. Regarding “D-connector” or “D-check” plug and CEL:

    THANKS Tony!!! That has been driving me crazy. That is something that needs to be labeled and/or called out in the owners manual. I just went through the same experience today, Yours is the first piece of info I could find on it. Again, thanks for doing the legwork.

  24. 97 postal legacy.. does speed sensor 2 input to ECM and if not working could it produce rough running and stalls?

  25. 95 legacy 2.2L engine light on, code reads misfire in 3 and 4. New coil,wires and plugs. Found Corrosion under ignition module, cleaned it, fixed problem for about 1000 miles. Could ignition module be problem or maybe crank senor? I think I’m close to the problem…. hoping it isn’t the cam. I have 240,000 miles and hoping for more:)

  26. Hey Kent,

    I would drop the exhaust down and inspect the exhaust valve guides to see if they have “shifted” Very common if it has single port exhaust.


  27. Justin

    I read about that after I wrote you. What is the fix if the valve guides have shifted. You mentioned sticky valves from sludge between stem and guide. Suggesting an oil flush and synthetic, and lube guard. Should this be done also/anyway? This is a very informative sight. Also, I read that the oil pump return hole is to small and should be 6mm, causing an oil leak between pump housing and cylinder block sealing surfaces…. should I worry about this? Wondering if the burnt smell we get is from that and/or missfire. Thanks again for the great information.


  28. Kent,

    If the guides have shifted it requires machine work to the heads, installing oversized OD guides and a valve job.

    If the valves are just merely sticky than a fuel induction service may help.


  29. Justin,

    Thanks for the good info here. I have a P0420 cat code on a 2002 Forester, and there definitely seem to be many possible causes. I read the o2 sensor voltages over OBD2 with the engine at operating temp and found that sensor 1 runs at 1.5 volts and does not change. The OEM Bosch part is spec’d for 0v – 1v. Does this mean the sensor is broken, fouled, or the cat is bad?

  30. Jeremiah,

    Which sensor are you looking at the first or second, also 02 is a split year in the Forester platform and the front 02 sensor is also referred to by Subaru as a air/fuel sensor and works in a different range as the 02 sensor does.

  31. Justin,

    The OBD2 tool specified bank 1, sensor 1. I’m not sure which that means. What range does the air/fuel sensor work in?

    As a follow up, I drove the car a little harder on advice from friends that hot exhaust is occasionally needed to keep carbon buildup out of the cat and off the O2 sensors. The engine started overheating, and when I checked there was no coolant in the overflow. My girlfriend (car owner) said the tank never holds coolant for more than a day, so she just fills it once in awhile. I filled it and it did not leak overnight. I suspect a leaking head gasket is fouling the O2 sensors with coolant in the exhaust. Any thoughts?

    Thanks for the help!

  32. i have a 02 outback and had to have the engine replaced in it in November ’06. The engine was replaced at a subaru dealership and since then i have had a “check engine light” on. I returned it to the garage and they cleared the codes and said it was fine…sure enough it came back on and i brought it to a different subaru garage and it was cleared TWICE and still is on. they said there was just a wire malfunction and it was no big deal….fast forward 2.5 years ahead (still the engine light is on this whole time) and now i just went last weekend to get the car inspected and the subaru dealership that replaced the engine, has inspected me for two years- wont inspect it because of the light. they said the state has changed thier standards and will not pass it ….so my question is what do i do??? i have been driving it around for over 2 years like this and two subaru garages can’t fix it and now they wont give me an inspection sticker!!! i have 60 days to “fix” the problem.

  33. oh i forgot to tell you waht codes come up! the cylinder 3 misfire and the theshold…i cant recall the exact code numbers but they are the same two that have come up since the engine replacement in ’06.

  34. Gina,

    If a check engine light is temporarily turned off and then comes back on as soon as the vehicle’s computer sees a problem then obviously something is wrong.

    I don’t understand why any Dealer service department would tell you it is ok to drive around with a check engine light on as it contradicts what is written by Subaru in your owner’s manual.

    I could go on for an hour or two about this and also why it’s always bad to involve a bunch of different shops, in your post you mention “the garage” have you been taking to a Subaru Dealer service department? I wasn’t clear on that part.

    Enough of what could and should have been done a while ago. The car is very fixable, but yes it is going to cost to have a real pro look at it, diagnose the real issues causing the codes that are set at this time and once that is done it is very possible for the light to come back on with new codes set. There are many codes and only one light. Add to that for each code there are many possible reasons for that code to be set.

    Driving around with a misfire code is never good, as to the Catalyst efficiency code there are a lot of reasons but if it has had a misfire for any length of time the catalyst is probably damaged as a result or may have been affected from the previous engine failure.

    If the Subaru has been taken to the Subaru Dealer service department on all of the occasions you have mentioned I would call SOA or at least have an in depth conversation with the Service manager at each Subaru dealership.

    I do want to stress though that you will want to look at the invoices from when the car has been looked at and look to see if there is documentation as too which codes have been set each time and were there any suggestions made that were not performed?

    What really needs to happen is a real diagnosis of the problem and corrective repairs in correlation with the diagnoses.

    Now I don’t know the Emissions laws in your state or which state you are located but some states will substitute a tail pipe test in lieu of an OBD test when there is a catalyst code set.


  35. Justin,

    My 2001 Forester had a stumbling at idle diagnosed as bad spark wire (replaced by dealer) CEL came on, temporarily off with upper cylinder cleaner added by dealer, back on with knock sensor code, sensor replaced by dealer, engine gasket leak, coolant loss, replaced by dealer, CEL on again. Gas cap tightened always. Car drives perfectly. What’s your guess?

  36. 2000 outback runs like a dream but CEL comes on every once in a while…stays on and then disappears. Code is P0328 KNock sensor 1 Bank 1. Right now i have not seen the sensor for a week. i wonder if the ethanol in the gas is the culprit? any thoughts

  37. Brian,

    The knock sensors on that era Subaru are very prone to failure; it’s not an expensive fix by any means. The knock sensor will emit a frequency back to the ECM when the vehicle pings, the computer will use this information to advance or retard ignition timing for the fine tuning of the engine. There is a little more to it than that, but that is the basics of how it works. A failed knock sensor will cause the ECM to go into a fixed or programmed set of timing values based on other data rather than constantly looking to fine tune the engine. So while it may seem to be running ok, you could affect fuel economy a small amount and an engine that is running as good as it possibly can, will always outperform one that is in need of tuning.

    Hope that helps

  38. Hi, thanks for this great forum.

    I have a 1999 Forester, the alarm/auto doorlock system had been acting like it was possessed for a long time, it was a minor annoyance and sort of amusing, (pass a police station or hospital and the alarm would *bleep* and *bloop* and all the locks would lock and unlock rapidly, making a machine gun-like sound), in any case, some time ago the car wouldn’t start, I had it towed to my mechanic who diagnosed a grounding problem with the ignition. He ran a new grounding wire and all seemed right with the world. although the next day the MIL came on. I need to take it to get the emissions tested and so brought it to the mechanic again and the scanner came up with code P1101 which he said was “Neutral Position Switch Circuit Malfunction (M/T)” Thinking that this had to do with the shifter lockout system and in my mind connecting that with the crazy alarm system I then had an auto alarm shop pull the alarm completely out of the car. Now the MIL is *blinking*, took it back to the mechanic, but the codes are not related in any way to the ECM that I can tell, they are: P500, P1101, P1121, and P1540.

    The Internet tells me that these are:

    P0500 – Vehicle Speed Sensor Malfunction
    P1101 – Neutral Position Switch Circuit High Input (A/T)
    P1121 – Neutral Position Switch Circuit High Input [MT Vehicles]
    P1540 – Vehicle Speed Sensor Malfunction 2

    OK, so I think I should have a question … how about: Why would the MIL blink if none of the codes being reported have to do with emissions or damage to the Catalytic Converter? Can I get the car tested and if they see that the codes are not related to emissions that they’ll let me pass. OK, I know that’s not going to happen, but argh.

    Thanks again for the great forum!


  39. Max,
    It’s hard to really understand all of the issues you are having, I am afraid you really need to take this car to A Subaru Experienced Technician preferably a good Independent Shop.

    Here is really all I can offer over the internet.

    The neutral switch on the manuals fails quite often, but will not cause a check engine light to flash.

    There is no way to circumvent the system especially with a flashing check engine light.

    Some of what you have written doesn’t really add up? Not sure how a ground was affecting the ignition switch that would be very unusual unless it was related to the alarm system. I suspect a cheap aftermarket alarm wasn’t installed correctly from the start and then the removal wasn’t done properly at all either some alarms have auto locks based on vehicle speed and if the speed sensor wires were tapped into incorrectly that would be very bad. Does the Speedometer still work? I suspect the code numbers aren’t accurate either and a generic scan tool is being used and not a real Subaru Select Monitor. Has anyone looked at/ diagnosed/tested any of the sensors/ switches in question?

    Probably a good Idea to have it looked at.


    1. Justin…thanks for all your great insights. I have a 98 Outback, just had the heater core replaced…had to pull the dash. Now I am getting a constant check engine light, with codes that seem totally unrelated to any of the work done. So based on prior posts, the grenn wire connection has been left connected. But in the last post, you asked if the speedometer is working. Mine is not and the mechanic has been unable to trace the cause. Could these things berelated?

      1. Woot,

        The green conectors should be disconnected, if the speedo is no longer working maybe you didn’t connect it?

        I am a broken record here, but the fact that the check engine light is on means nothing to me, I cant help you at all whatsoever with out a code number.

        If the light is on and you have a knock sensor code like po325, p0328 its probably not related to the Heater core, if the light is on and a code for the VSS, or Vehicle speed sensor is set well then yes maybe something isnt connected, or is broken.

        I like to help, but without more information there just isnt anything I can offer.


        1. Still investigating…but wanted to say you have generously provided so much info to all of us, you need to be thanked again and again.
          You should take $$ contributions!

  40. I guess i have a similar problem with my engine light just went on today…and i’ll check gas cap? I’m on vacation though and wondered if i could drive my car 400 miles if the light is on…i really would like to check out the problem at home…unless the light goes off after i check the gas cap.

  41. David,

    After inspecting the gas cap, if you have found it loose it will take a few drive cycles before the computer will clear the check engine light. It may be wise to have it scanned at a parts store since you are on a road trip, most of the time it is just a drive with caution kind of a thing but there are a few codes that can be set in correlation with bigger problems that should not be ignored. At least knowing what code is set is a good thing to know before getting back out on the road.


  42. Hi,

    I’d have a question regarding the cel on my 2005 outback H6 3.0R. It came on last week, with the cruise control light flashing (wich is normal with the cel being lit up). When I hook up my code reader, it gives me no codes at all, no error messages, but it does link correctly with the car. The car runs fine and fuel consumption is still the same. I did disconnect the battery and emptied the residual current, the code went but next time I drove the car it came back. Same story, no codes with the reader hooked on. I did check my fuel cap to be sure it was tight.

    Can the fuel cap leak make the cel appears, and would thatbe the reason why I can’t see any code when I connect the reader?

    Thanks for any light you can shine on that matter,



  43. Steve,

    I don’t think your code reader is working properly on your Subie. This is very common.

    Try to not disconnect the battery or clear the codes it makes the job of diagnosing it harder. When you dump the memory or clear the check engine light you are erasing valuable data that can assist in diagnosing the problem.

    You have a code set the code reader isn’t capable of reading, this is very common some only read OBDII codes. Meaning any Subaru specific codes will never be shown (and there are plenty)

    You are at the end of what your tool can do for you. I would have Someone at least perform a Diagnoses preferably a Subaru Specialist and go from there.


  44. I own a 2002 Subaru Outback with 162,000 miles on it. I purchased this car new with 9 miles on it. My husband is a fanatic about oil changes and it has had its oil changed every 2,000 miles usually–sometimes it would go to 2,500 miles. Suddenly in January of this year my car has started requiring me to add 1/2 a quart of oil in between the regular oil changes–I know this is not a lot of oil, but its just not correct to me. There is no oil leaks, there is no smoking, no loss of power, no change in fuel economy. The car runs great and there is no check engine light on. I love my car and planned to keep it for another 150,000 miles, but now I am worried. Any ideas?

    BTW you are really good and explaining things and I appreciate your site.

    Thanks for any suggestions.


  45. Hi Lisa,

    Thanks for the feedback on the website!

    There are a few different things to inspect; the first is the PCV (Positive Crankcase Ventilation) system.

    Sometimes the PCV can become stuck open and this can cause a host of problems including oil consumption. The valve is located in the intake manifold, passenger side near the throttle body.
    If the car is running too rich it will consume more oil as the oil becomes contaminated with fuel and the flash point is lowered.

    Sometimes the type of oil used can affect things as well. This is because some brands will use different refined oil bases, purchased from different refiners and merely add their additive package in. This may not apply here for you but it is worth investigating.


  46. I have a 2000 Outback with the opposite problem of most posts on this forum…The MIL bulb appears to be burned out. It does not come on when the car is first started. The car went through the CT emissions test yesterday and failed because the light did not illuminate. They said we must get the bulb replaced before going for a retest. All other sensors passed the test. So, can I replace the bulb myself or is this going to cost a small fortune?

    BTW, this is a great forum.

  47. Justin,

    I have a 99 Subaru Impreza. Last year while in Utah, the car bogged down when accelerating. I took it to a Subaru dealer and they told me that the left side exhaust flange bolt was “out of head”. They told me they tightened the bolt as much as they could but I would need a new Y pipe flange and that I would need the head “heilcoiled” to reair the stipped out bolt. It worked great for the next year with no further repairs. However, recently it failed the California Smog Check. Idle, HC measured at 102. 2500 rpm HC measured at ten. The check engine light is now on with a P0440 code. The garage (not a Subaru dealer) told me that it was most likely the catalytic converter and that my car has two of them. Does this make sense?

  48. John,

    Its hard to say if you should try and replace the bulb your self as I dont really know your skills or the content of your toolbox.

    I would suggest replacing the check engine light bulb and all of the main illumination bulbs while the cluster is out.

    I would say a price would be anywhere from $100.00 to $150.00 as a guess.


  49. Steve,

    It doesn’t make sense to talk about a catalyst issue with a p0440 evaporative emissions leak code set?

    Is it possible the code number was p0420?

    It needs to be diagnosed locally I suspect a vacuum leak or there is an exhaust leak, but there may be no correlation between the code set and the HC readings.

    Installing a time cert or helicoil is a straight forward repair why not take care of it versus the potential of burning a valve if there is a small exhaust leak at the flange? Also I don’t understand the reason for the y-pipe if there is thread problems in the cylinder head.


  50. Justin,
    Just wanted to thank you for an excellent and informative site. I’m having recent issues with the steady CEL and flashing cruise control light on my 2006 Forester (both my husband and I have 06 Foresters–here in Colorado, it’s a must-have car). Checked gas cap, which was fine, so must be another emissions problem. Am taking the car to my local Subaru dealer where I bought it (and which has peformed all the maintenance on the vehicle to date) this week to have it diagnosed and handled.
    I’ll definitely be coming back to your site to continue to learn more about my Forester…and to seek your advice should I have future questions on its performance.
    Thanks again!

  51. justin,
    i have a 2002 subaru forester. over the past few months, i’ve had this scenario happen about 4-5 times. i start the car and it idles kind of unsteady. i start to drive the car and the check engine light flashes and when i step on the gas, the car barely goes forward at all. then, about 30 seconds later, the check engine light will become steady and the car will run normally and the problem won’t happen again for a few weeks. from looking at other responses, my guess is a loose ignition wire. what do you think? in any case, i’m going to change my spark plugs and ignition wires. thanks for the help.


  52. I came here with many questions, they’re all answered now!! Justin, what an amazing site. I own and love my Subaru and live not too far from Kirkland and consider myself lucky. I’ll be finding the place soon!

    The CE light wouldn’t be so bad if there were more f’n gauges to give a clue. Like I need an encyclopedia, but I’m given a bible.

  53. Pete,

    Also check the plug wires for signs of oil, if there is any present the spark plug tube seals are leaking oil into the spark plug tube. This is very common.


  54. Just a quick note in reference to John’s post #53.
    My CEL (97 Impreza) was coming on, and after 2 drop off to my local mechanic, he finally fixed it.
    Well the other day I took my car in for a NJ inspection, and it failed because the CEL was ‘burnt out’. Being a hands on guy (oil changes, belts, aftermarket radio, etc.), I decided I would get to this bulb. Well, I took apart the instrumentation, and lo-and-behold, there is no bulb behind the Check Engine Indicator!!! There they are behind the oil, ABS, etc… but nothing behind the Check Engine!!! OK, I know I can be a pessimist, but funny how that is the only bulb missing.Well, off to the local dealer to get this bulb, and hopefully it won’t be lit when I put it in.

  55. Just as a follow up to my previous post, Looks like the bulb was just missing. I’m not sure how the bulb would back out, or why, but I installed the new bulb, and the check engine light came on when the key was put in the ignition, turned off when the car started, and so far has stayed off.

  56. Justin,

    I have a 1994 Legacy with 230k. It has been driving like a champ and I just had a 60k service done on it (bad water pump, decided to get the service out of the way). But, my check engine light problem started showing up before I took it in and I forgot to mention it. It is still occurring, and the symptoms are something along these lines:
    -When I start cold, there is no light.
    -After some time, it will come on, but I do not notice any change in performance.
    -As my speeds change, it will toggle, but it usually comes one when I slow down after it is warmed up.
    -When I accelerate, it will toggle off; usually about when I back off my acceleration, like when I have reached cruising speed.

    I’m basically interested in some possible causes to get an idea of what I might dinged for.

    FYI, I’m in Snohomish


  57. Thanks for this site. Just discovered it and it answered a lot of my questions. I want to be sure I am getting the best service so I thought I would ask about my problem. I have a 2001 Forester. The CEL has been on for about two years but decided had to get it fixed because the car started bucking and hesitating. The codes that came up first diagnostic read was p0420 and O2 sensors and fuel sender codes, po463. Had it read a second time a few weeks later and the po 420 code disappeared. Gas cap code came up. Had the o2 sensors replaced and the gas cap replaced, hoping that would do the trick, but CEL came on a few days later. I also have a small hole in the exhaust pipe and I was told there may be a leak in the block (not losing any oil as far as I can see). I have to go through emissions check in a month. Why would the po420 code disappear? What would you suggest I fix first to give me the best chance at fixing the problem?

  58. Hello Justin,

    I’ve been having a wonderful learning experience reading this forum. I do have a problem with my Subaru though. It is a 99 Legacy OUtback Limited with the 2.5 liter engine. For a couple of years now, my check engine light has been on intermittently, but I’ve been putting Lucas’ fuel treatment in the fuel tank twice, once with premium and second with regular. Afterward I drive for a couple of weeks without doing anything and the check engine light goes away. However, I am tired of this light being on. I forgot to mention that the first time the check engine light came on, it was a P0420. I’ve also gotten codes for knock censor failure and O2 censor failure, but those codes clear up by themselves without any treatment. Tomorrow I am going to bite the bullet and get my subaru read at the dealership in Memphis, TN, and hopefully the check engine light won’t require to hefty of a repair. However, if you can think of something that could lead to a P0240 wihtout the cat actually failing or not function at threshold, that would be great. I’ve not had a problem with a leaky coolant system or oil. I am curious though if the use of 10% ethanol in regular fuel is causing my problem. I’ve also been able to pass the emissions test every time since I’ve owned this car, though this year I did have to have the emissions done twice at the same time, though maintaining and engine speed of 1200 rpm during the second reading. Hope you can help me with this and anyone else who has a similar problem.

  59. Mike,

    It needs to be scanned for codes, and then the code/ suspected failed component diagnosed. The most common component failure that year would be a CPC (Canister Purge Control) but I can’t stress enough without diagnoses this is just a guess.


  60. P. Costello,

    Like I try to point out in my article, you have emissions system monitors that monitor each system at very specific drive cycles, if the system isn’t at ready status, or the car isn’t driven in the manner at which based on the computers programming it will look at the catalyst it won’t set the check engine light.

    I know it’s just a car and most really want it to be simple, it just isn’t and very misunderstood, like how someone replaced O2 sensors on your car while you have an exhaust leak tells me the shop doesn’t completely grasp OBD II (On Board Diagnostics II) an exhaust leak alters the O2 sensor values and can affect how a car performs and should have been addressed before any O2 sensor work was done.

    The catalyst code will come and quite often, as it is not always being monitored and the temperature of the exhaust will affect the efficiency of the catalyst as well.

    I am not picking on you but anytime I have a conversation or read a post that starts out with “my check engine light has been on for two years” I cringe as I am ever in the difficult spot of trying to explain why that is a bad idea, and have to listen to “well it runs fine” at the same time. Just like you could go to the doctor and be told your blood pressure is high and feel just fine, but the long term consequences can be brutal, this is the same as in your car if the light is on, something is wrong and there may be long term ramifications of leaving the light on. The problem is there are hundreds of things that can happen and only the one light.

    I would look into the exhaust leak first, have someone perform a catalyst test, not a code scan but a efficiency test with propane, and a 4 gas analyzer, if the catalyst has failed maybe replace it. Also is the possibility of a new code that needs to be diagnosed.


  61. Andrew,

    Ok, the codes don’t clear themselves up, it’s just that for a certain amount of time either the computer didn’t monitor the suspected systems or the systems were working ok at that time as there are a lot of variables. Slow 02 sensors can lead to Catalyst failure, a failed knock sensor to all sorts of long term problems.

    The catalyst should be tested if anyone out there besides our shop still knows how, as far as emissions every state is different, in mine if the light is on with a po420 you fail.

    Yes sometimes different gas can affect the readings from the 02 sensors, which can be misinterpreted by the ECM as a catalyst function issue in some extreme cases but it usually points to a catalyst that isn’t getting hot enough either. So a weak catalyst is exposed with different fuels in a way. There is much more to it than that but I find it really hard to explain in a reasonable amount of time catalyst testing, function, and drive cycles. O2 readings, how the ECM actually works, how it only looks at certain things at certain times and why it will turn off the check engine light after a while if it doesn’t see a problem.

    I really think the Government got it way wrong with OBD II and the one light to rule them all thing.

    It’s just not as easy as drivers want it to be.


  62. Thanks for the info, Justin. Much appreciate you taking the time to share your expertise and knowledge with me and others. And I will never, ever ignore the CEL again! PC

  63. Man, I love the internet and google as it brought me to this site. I own a 2006 Subaru Legacy Sedan and it has just under 29,0000 miles on it. Today when I started the car it seemed to be running a little rough and then the CEL came on and my cruise control light started flashing. The CEL was flashing at first but then just stayed steady on.I was only driving 2 miles round trip so whenI got back home I pulled out my owners manual which led me to check the gas cap. It seemed like it might of been a little loose but I’m not sure but I took it off and made sure it was tightened down.

    I figured since the maintenance schedule shows the plugs and wires to be changed at 30,000 I would start there as it needs to be done regardless. I have always been good about my oil changes and I recently had my car inspected in June with no issues.

    A couple of weeks ago my check engine light came on and the car was running similarly but it went away within say 20 miles of driving. I thought maybe I had gotten some bad gas. Its been Seattle weather and raining almost non stop here in NY.

    However since it came on again today I am more concerned. Should I try replacing the wires and plugs first and see what happens? Is it possible it is bad gas again. I hate as a woman to take my car to a shop because they often want to blow smoke up your tookus lol. It seems from reading here I could get the codes read for free somewhere. Normally Id replace my own spark plugs but since there is a some kind of issue here I hesitate to do so with this subaru. ( my last one was an outback and I replaced my own plugs and wires in that without an issue)

    As far as the car running rough it seemed to be more right after starting or when Idling not when I was up to speed which since I was in my small town and only going a mile was about 40mph.

    I like everyone Im sure want to do this the most cost effective way but I need it to be effective lol.

    Anyhow, I got a little rambly here for which I apologize.

    Thanks in advance for your advice,


  64. P.S.Out of curiosity I just went outside to start my car. Beings I hadnt restarted it since I had checked the gas cap and retightened it. The CEL is still on but its not idling roughly at all. SOunds just like it should and runs smoothly as I drove it around the block.

    I understand the check engine light might not reset right away. Should I get it read at the auto parts store anyhow and go ahead and do the plugs and wires now?

  65. My 2005 Outback shows P0032 H025 Bank 1, Sensor 1 Heater Circuit High on the OBD reading. Is this serious? My car is running the same, but the muffler has sounded a little loud lately. Not sure if they are related or not. Is this something I should take to my Subaru dealership or to the local garage?

  66. P.S.S.

    Ok car seems to run fine .. idle fine.. yes the CEL is till on. Could it of just bee n the gas cap? I Did take it to Auto Zone and they red it with that reader. It said cylinder 3 and 4 misfire. Could that of been caused by the loose gas cap?

  67. Melissa,

    A misfire code shouldn’t be ignored. You can start with the plugs and wires if you like, but a visual inspection of those items first might be a better idea.

    29k is real low to be having a problem with the plugs or wires the plugs are due at 30k yes but not because they are expected to fail by then. Do you live in a rodent populated area?


  68. Rodent Populated area.. well I live in a rural area but there are alot of chimpunks, mice as well as some of the bigger rodents that run around… You thinking one of em got up in there and chewed on one of my wires?

    I know the minute I re tightened my gas cap all the obvious symptoms of rough idling etc dissipated. I bought some plugs but they didn’t have wires for my car at auto zone so I plan to take it to a repair hop an have it further checked out. As you mentioned my miles are low especially for a 06 model. It does however say in my maintenance book that 30 k is where I’m to replace my plugs.

  69. My local Subaru dealer says that my 2002 Forester has a code P0420. Also, the exhaust has a pretty pronounced smell. He recommended that I replace the cat, but cautioned that a non-genuine Subaru cat might not turn my check engine light off, causing the car to fail my state’s (TX) emissions test. In your experience, will a universal cat turn the check engine light off? Beyond the lower life span, what are other drawbacks of a universal cat?

  70. Omar,

    I would advise against the Aftermarket Catalyst, they just dont work well at all. You might as well light a match to the money you were planning on spending on the aftermarket parts.


  71. HI Justin, First i want to say that i learned a lot from your website…very helpful. Long story short – my dad is a very handy man and my whole life i have driven the 77 mustang he fixed up for me until i graduated college and moved from CT to WA for my first job… needing a reliable car (since my dad the mechanic would be cross country), i purchased 2005 subaru forester. I love it and have had NOT ONE single issue with it. Now the problem.. my boyfreind is in need of a car and after much shopping around we decided upon a used 2002 Subaru IMpreza OUtback spt awd. It has 160K miles on it and only one owner. WE bought it last night and on the way home the CEL came on and this morning the code read P0420. I took the advise of your blogs above and have an apt today at a Subaru dealership to properly diagnose the problem (which we think is the cat converter and if so will not go with an aftermarket one). THE QUESTION: it is not too late for us to return the car to the used dealership we got it from…in your honest opinion do you think it will be SUPER costly to fix this error code and will more arise? We really like the car otherwise. would appreciate any advise and of course your honest opinion
    thanks , jenn

  72. Thanks. I learned a lot from this web page (I just spent $35 to find out my gas cap may need to be replaced) but hey, everyone’s got to eat. I appreciate all the great info here.

  73. hello,
    I am trying to figure out a code P0403- EGR circuit malfunction. Its on a 1996 Legacy Outback. Is it as simple as replacing the selinoid or what should I check? Only other information I have is it only takes a few miles for the code to come back after being cleared. No parts have been replaced yet concerning this code.
    Thank you in advance.
    This is a great blog, good job!


  74. I have a 2002 Subaru Outback. About a month or so ago, my engine started running rough, I refueled with premium, and ran a fuel cleaner through the system. Ran fine for about a week, then suddenly one day..about a month ago: it suddenly ran very rough. Got the code that says there is a problem in the 4th cylinder.
    Took it to a Subaru auto repair, and they:
    changed the spark plugs and wires, the distributor coil, the fuel filter, the injector, the computer (to see if there was a different code), etc. Then he took it to Lithia in Portland, Or: they ran it through all the same tests and even hooked it up to some “super brain computer”: they came up with NOTHING except the same code.
    It is still missing. He then took the cylinder head off, found nothing. He’s at wit’s end, and gave me the car back to drive and see if will get worse and show the problem. The engine is still missing, the check light is flashing and I’m at wit’s end. Any ideas?

  75. Lyn,

    Most likely it has a valve out of adjustment, if it is missing it should be very easy to find.

    Hooking up to a Super brain computer also known as the Subaru Select Monitor will not yield good results. This device is good for looking at sensor data, but a misfire in one cylinder usually is not a result of a sensor so that is most definitely the wrong approach. The only thing that needs to happen is for the car to go to a Real Expert, the car is very fixable. I am often shocked at what I hear transpires at other shops. We would keep your car until we figured it out and would not replace any components unless it was to fix your problem.

    Most of what you have posted doesn’t really add up and I hate to say this but the injector, plugs and wires and coil should have been replaced only if found faulty. Unless I am missing something I have no idea why a Good Independent Subaru shop would send you to the Dealership as they really are not capable of the tougher repairs in most cases, it’s just not what they do.

    Most likely if a vacuum test is done it will be found to be erratic. Other than that you need to find the right shop in your area. That is the best advice I have for you


  76. Justin, I have read most of this thread. Thanks much for the huge amount of time you have already out into this.

    If you don’t mind a teensy bit more: my 95 legacy has the engine light on, it’s been a few months. At the outset of this thread you stated that pre-96 engine light has quite different ramifications. Could you say anything about that?



  77. Dear Justin,
    I have a problem that I haven’t seen addressed here. We have a 1999 outback with almost 100,000 miles. about 4 months ago, the check engine light went on; took it to our local mechanic who has worked on the car before; I do not know what the code was, but he said that it possibly indicated a problem with the emission controls; they checked everything and it all was within specs, so he cleared the code, and it was fine for over 4 months; the light came on again (again, with zero symptoms–car is running like a top); we took it to him, amnd he said that he is unable to access the computer to read the codes. He’s never had that happen, and his scanner is working fine (and was able to read it before); we have an appointment with Subaru, but I wonder if you have ever encountered this? I would think if the software/firmware/hardware was corrupted enough that he would not be able to read the codes, that more problems would be evident. I was tempted to remove the battery cable to reset the computer, but since we are taking it to Subaru, that would be stupid.

    Any thoughts would be appreciated.

  78. i have a 2002 subaru forester that has a check engine light on that is flashing why is it flashing and not constant

  79. Hello Justin,

    I have a 1998 Forester. I had a CEL for a 0420 (i think that was the code). It was for catalyst inefficiency. I replaced the oxygen sensors after lots of research because mechanics wanted to just replace converters.

    I replaced all of the pipes and muffler previous to that. The light has not come back on, however, when I took it for inspection it failed because the evaporative system is still indicating not ready. I have driven this car for at least 300 miles! I was told to fill the tank full of gas and check the gas cap and drive it around some more.

    I understand the system goes through I think 4 steps to get to a ready status or to throw a code…what could prevent info on this system from getting to the computer?

    When the 0420 code went off previously the mechanics had advised me to replace the fuel filler tube as well so that has been done.

    I have lost faith in my subaru specialist because I have spent so much money on this car. I am not sure that they are really taking the time to diagnose the problem but rather see a code and want me to fix what ever the code implies. With 190,000 miles they did not even suggest my replacing the oxygen sensors originally…i had to research and figure that one out myself.

    Please any assistance you can give would be appreciated! thank you, -Erika

  80. Justin-
    So i had this problem with my 2003 Forester concerning the head gasket leaking coolant, which the dealer has decided to ignore. I have 106,000 miles and the problem was just recognized after i had the coolant flushed (trying to do the right thing)Now i’m exploring ideas of how to fix it and i just make sure the reservoir is filled. Today the check engine light flashed three times and then disappeared. What the heck is going on here? Is there a Subaru Independent shop somewhere near Northampton, Massachusetts??

  81. Erika,

    It has to go through a cold soak period (typically overnight) and then have a drive cycle performed to reset the Evap monitor to ready status.

    This can happen with time as well, but it needs a certain number of drive cycles to reset to ready status.

    With out a scan tool that can read data there is no way to do a proper drive cycle, all you can do is wait it out..

    It will reset it self.


  82. Hello David,

    The light flashing indicated a misfire. I would keep a close eye on that situation.

    I am sorry but I do not have a shop to send you to in that part of the country.

    This comes up a lot,I meet more people every year and now have solutions for Subaru owners in other states, but not Mass as of yet.

    If you want an idea, look for Subaru’s with a shops license plate frame on it, and then ask the driver what they think of the shop.

    Just a thought, one way in which some of our customers have found us outside of the web.


  83. I have a 2004 Forester w/30K miles. The CEL is on with codes P0303/304/420. This started happening after we left the car outside on a cold night and the following morning was humid and warm. After failing to start, I popped the hood and saw that there was dew on all the plug wires. Later in the day when it had dried out it started and ran fine but the CEL was on. I replaced the wires , coil and 2 passenger side plugs. I still have to replace the driver side plugs, they seem to be a bit of a challenge. 2 questions: Should the CEL go out on it’s own after a while or do I need to get it reset?
    Also, any tips on replacing the 2 driver side plugs? Also, I got Iridium plugs which claim to use less voltage so should be less prone to misfire on damp mornings.
    Thanks for the site, Pete.

  84. I recently bought a 04 Forester XT w/ 118k Miles and it is idling very rough, and getting about 10 MPG. The CEL is P0031 H02S, Heater Cntrl, Circuit Low, bank 1. Where should I start?

  85. hi, Justin,

    Thank you for this great forum, it’s really helpful.
    My 1996 Subura Legacy CEL recently turned on for twice. The first time it turned on after I pumped a tank of Kroger gas, I stick on Bp gas for last 3 years. Then the CEL went off by itself when I switch back to Bp gas. The second time it turned on after I pumped a tank of Speedway gas, there is still half tank of speedway gas now. I’ll check if the CEL go off if I switch back to Bp gas again. Is it possible that the gas of Kroger and Speedway contain low ethanol contaminated my emission system? Thanks.

  86. Hi Justin,
    I have a 2005 Forester with 150k miles on it, and we’ve had no major problems so far. My CEL came on steadily and my cruise light started flashing a couple days ago. I checked the gas cap which didn’t help, so since I was about a block from my dealer, I went over there to get things checked. The service staff told me that I might need to replace the catalytic converter, but they may be able to prolong the life of the current CC (without replacement) by “flushing the emissions system”. I didn’t know this was a system that could be (or should be) flushed, and I can’t find any info about what that entails or how it would help. Do you have any insight?

    Thanks for the time you take with this forum!


  87. My 2001 Outback has had the cel on for quite some time with no drivability problems until recently. Under medium acceleration the car will buck once or twice then be fine. This morning I was passing someone and the car bucked. The CEL also flashed on and off. I pulled over and restarted the car. The CEL quit flashing and it is back to the way it was. What can cause this and why would the light stop blinking?

  88. In response to “Max Says: June 30th, 2009 at 5:42 pm” post, I laughed uproariously at the alarm description. I’ve had the exact same thing happen to me (2000 Sub Forester S).. How I solved the problem after the mechanic was afraid to pull out the alarm wire (that would disable the engine), I simply cut the alarm wire under the dashboard. Naturally this meant I could no longer use the alarm button to lock/unlock the car, but manually open the car with keys.

    Once in a while, the alarm will go off by itself and engine disabled (can’t turn engine on). I just hold the cut wires together, turn the ignition and after the engine’s on, I pull apart the wires.

    That did the trick for me.
    Laura B.

  89. I have a 2002 Subaru Legacy Wagon with 195,000 miles on it. The CEL has been on constantly for the past 3 years. I’ve had it in the shop, spent mega-bucks for the mechanics to take everything apart and check for all of the above-mentioned possibilities…he found nothing. The Subaru service folks were not able assist. I just decided to google this problem, and I couldn’t believe what a common problem this is with Subarus. Other than that, the car is great…I am looking forward to trading it in before I fail another state inspection though.

  90. Further, if your CEL comes on and off intermittantly (as some here have mentioned) regardless of code, suspect the connection FIRST before replacing a quality OEM part with some cheap grey-market component from Kragen or Autozone.

    Emissions, as in carpentry, should always be approached with a: “Measure twice, replace once” philosophy.

  91. Came across this thread in a random search, my 2007 impreza’s CEL kicked on, with the blinking CC. Fortunately I’m in Seattle so I’m just going to schedule an appointment with Justin’s shop! 🙂 This thread should be an example of how letting your experts talk about what they know will get you business

  92. My 96 2.5 subaru legacy is drinking gas like a v8, the check engine light stays on and it idles very ruffly. I just bought it and would love to keep it going. I was told that a blown head might be the reason. Please say it isnt so, the car dont smoke at all. and it picks up speed just fine. had a tune up done and still have the same results. once or twice it has cut off, but starts right back up. please give some advice.

  93. The CEL came on in my 99 Outback, after hours of checking fluids and everything I could think of I discovered that the gas cap was not tightened all of the way. This is what I get for filling up in Oregon. I read the idea of disconnecting the battery for 30 minutes to an an hour, and also letting the car go through a few drive cycles. Do you have any other ideas?
    Thanks a ton.

  94. Mine is an automatic 1993 Legacy SW. Got a new and an old problem. Please help.

    1. This week in 2 different ocassions I being driving normally and suddenly the engine goes to Neutral. Engine raves as you press the gas pedal but is just in neutral. Shifting to 2nd or 3rd doe4s nothing. I shift to 1st and then it moves again. I go to 1st, and it starts moving again. Go back to drive on both opportunities and it just being fine for days.

    2. About 10-12 times a month the car won’t start when the key is inserted. I have to take it out, or change back and nofth between Neutral and Drive, until it finally goes ON. Someone told me thats normal in all Legacies, iis it right_?

    Note> I hope I were in the States and not in Colombia where the only Subaru dealer is a fiasco!

  95. Thinking of buying a 2000 subaru legacy with 195K on it. Nice shape. Check engine light on. Two new after market cats this year. Light stayed on. Two new Subaru 02 sensors. Light still on. Light stays off for a day but comes back on. Will it pass inspection in NH if light is off when brought to inspection shop?

  96. Ross,

    When the check engine light comes on in your Subaru there is a code set, if the parts replaced don’t correlate to the codes set, the repairs will never keep the check engine light off in your Subaru. So if you have a PO420 Catalyst efficiency code and after market catalytic converters are installed most likely it wont fix the problem, there is a reason they are less and they do not last.

    Also there are other things that can cause this situation, has it ever had a real analysis?

    I don’t mean a code scan, a catalytic converter efficiency test with propane the only real test that should ever be done.

    I don’t know the laws in your state but I would venture to guess no.


  97. I have a 2001 subaru legacy gt with 160,000 miles. The check engine light was coming on as a 0420 emissions problem and a knock sensor issue. I replaced the knock sensor and the light went off for 1000 miles and then came back on. It had the same code and then went off again. Last week the light was off but the car only got 16 mpg compared with an average 23 mpg. I don’t know if I should try replacing the O2 sensors or just swap out the cat…

  98. Justin, ’97 Legacy Outback Limited, 158,000 miles. Question ? Will a bad knock sensor hurt performance at all or simply irritate me with the CEL? The autozone scanner says knock sensor is bad. Should I replace it ?

  99. Ian,

    Without testing the Catalyst its all just a guess, you can try the o2 sensors and then some sort of treatment to the catalyst. But if the Catalyst doesn’t recover you will have spent some money to get no where.

    You cant properly test a Cat without a gas analyzer and propane, and the knowledge of how to perform the test.

    Hope this helps


  100. Tim,

    The knock sensor is there for the fine tuning of the engine, if the computer no longer sees a knock sensor signal it will no longer adjust the timing as incrementally as it would if the knock sensor could send a frequency to the computer when the engine vibrates as a result of the ping.

    Instead it goes into a more fixed set of parameters, load and throttle equal this much timing advance. This over time can cause increased fuel consumption as well as take way longevity of some of the engine internal components.

    The knock sensor is $100.00 on average, its worth replacing.


  101. First, let me thank you for the information you’ve provided here. Now, to ask my question. I just bought (4 hours ago) a 88 Subaru DL. The check engine light flashes on and off. I think (and could be wrong) that 88 was before ODBC was put in cars so I’m kind in the dark as to what it could be referring too. Suggestions before I take it to the mechanic?


  102. Justin, ’97 Legacy Outback Limited, 158,000 miles. Question ? Will a bsd knock sensor hurt performance at all or simply irritate me with the CEL? The autozone scanner says knock sensor is bad. Should I replace it ?;

  103. Stu,

    You can locate the D check connectors they are located on the drivers side just behind the strut tower, connect them and obtain the code.

    I would suggest buying a Service manual for the Loyale, and no not anything else other than the O.E. Subaru Service Manual.


  104. Help! In the past nine months, my CEL has come apprx 6 times. Each time, I have taken it to the same certified Sub dealership where I purchased my 04 Sub Impreza. It is not a turbo and currently has 109k miles. I have had it maintained pursuant to Sub recommendations. I have had my 02 sensor replaced, gas cap replaced and solenoid replaced. They have also checked the evap system and was told that was not the problem. Moreover, each time I am told the problem is resovled and it is completely coincidental that the CEL comes on within a day or so of refueling with a midgrade gasoline. What is going on???

  105. Justin–Thanks very much for the great site. My 2003 Forester with 114K miles has had the CEL on many times, but this time the mechanics I have taken it to for many years could not fix–they say the scan indicates a leak, but the smoke test shows nothing. They reset the CEL but it came right back on. Any suggestions?
    Thanks again–

  106. Justin,

    I have been having ongoing CEL light coming on issues with my 05 Outback 2.5i. I brought it to the dealership, the only mechanics with whom I will deal. They couldn’t replace the CAT at first because the O2 sensor was shot. I replaced the O2 censor. A week later, the CEL light came on again. I brought the car back in, and this time, they replaced the CAT. I thought all was well, but once again, this morning, the CEL light came back on. What can possibly be left?

  107. Pam,

    Without knowing any of the fault codes set in correlation with the check engine light coming on in Your Subaru its really tough to offer any advise.

    Hopefully the dealer you are taking it to is documenting the codes on the invoice?

    As to why the light comes right back on after fueling could be you are not getting the gas cap tight or the cap is faulty?

    There are a thousand other possibilities you need to put some pressure on the dealer you have been taking it to.


  108. Tom,

    With out knowing the codes I cant really offer much advise. There is one light and hundreds of codes that will trigger the light to come on, it is a system that needs an update in my opinion but that wont happen for years to come.


  109. Josh,

    With out a code the advise I can give is limited.

    I assume you had a P0420 set, but I guarantee that there was no real converter test that was performed, there is no reason to replace any parts without a proper analysis, but most just don’t take the time.

    You can set a 420 without there being any issue with either the catalytic converter or the 02 sensors.

    You need to put some pressure on the Dealership, and I will also tell you you should consider expanding you horizons to include a good Independent Subaru shop.


  110. hello i have a 2006 tribeca. one day while driving my gear felt like it skipped (btwn 30-50 mph) and the sports, no traction, and abs lights came on.
    the sports light keeps blinking.
    what is that?

  111. Sim,

    You also should take a moment and open of the glove box, grab out the owners manual and look into the meaning of the lights for your self, I realize its not very exciting reading but its really better to be informed.


  112. I have a 2004 Subaru Outback with 144,000 miles. My check engine light can on this week and when I did a diagnostic check on it the code read P0483 (Cooling Fan Rationality Check Malfunction). I have had 2 different mechanics just look at my fans and they said nothing looks wrong with them. Do you have any ideas about what might be the problem. I really want to know what might be wrong before I go to a dealership and am overcharged for something that might not be wrong.

  113. Morgan,

    The cooling fan rationality code means the cooling fans are coming on and staying on for a longer time and more often than the computer anticipates, you have a cooling system problem and most likely a head gasket issue.

    It sounds like the “mechanics” looking at the car are not all that familiar with the Subaru.

    Hope this helps


  114. Hello Justin, 1997 Legacy Outback, 158,000 miles. New head gaskets, plugs and recently replaced knock sensor with good results about one month ago. Now check engine back on and flashing at times. Car feels like it’s only running on 3 cylinders. I have a 0303 code from auto zone store. Any thoughts?
    Tim Smith

  115. Hi Tim,

    You really need to look into the misfire, it could be a plug, wire coil, valve adjustment, injector etc. I would start with a cylinder leak down test if it was here.

    If it didnt run like that prior to the head gasket repair than I would go over all that was done. It may be something simple that was missed or something like a valve that was damaged as a result of the head gasket failure and not caught during the repair.


  116. I bought a 91 Legacy a month ago. I had a mechanic look at it ahead of time. He said that check engine light was on cause it needed a knock sensor. It has been running like a top. But yesterday a friend changed the knock sensor and changed the battery for me. It ran fine when I drove it home 10 miles. But this evening when I started it up it idled VERY rough. Friend suggested car had forgotten its settings when battery was disconnected, and that I should disconnect negative for a few minutes, then drive at constant speed on the freeway for half an hour. Did all of that and it still is idling VERY rough. Any ideas? Does it just take a few days for settings to reset themselves (but it drove home fine last night). Could newly installed Knock Sensor be bad? Ran perfectly before this.
    Thanks for any input.

  117. Hello Justin,

    First of all, thanks for this great blog, it’s a great help for all of us with wuestion about our cars.

    My question concerns my 2005 outback h6 3.0R. It’s throwing a code, the p2135 wich is about the throttle position sensor. it’s an intermittent problem. It happens randomly in all kind of different conditions. When it happens, the car gets in limp mode and the engine is all shaky when in gear. I’d be curious to know what you think about that.

    Thanks in advance for your answer.

  118. Hi Paul,

    ITs really hard to say, a faulty knock sensor wouldn’t cause that type of issue, and neither would the battery, the only thing on a 91 the computer really has to learn before its drivable is base idle speed, which until it does would cause it to idle low or high but not rough.


  119. This happened to me when i let my Forester run out of fuel. Seems to mean nothing as i’ve done over a thousand miles with the check engine light on and apart from the light being on constantly the car runs perfectly.

  120. My ’04 Subaru Legacy has had the CEL on since 2006. I’ve had spark plugs changed, a new ignition wire set, and multiple visits to the dealership and the following codes consistently come up: P0303, P304 and P0420. Dealership suggested replaying the cat converter (eventually), which I haven’t done yet. Car sputters from stop position and RPM’s race to 4000 while car is traveling 5mph at best. What’s my next move? Change o2 censor, replace driver’s side cat? This problem drives me insane. TIY!

  121. Dear Justin,
    I have a 97 Outback 2.5, 280K miles. Prior to my purchase, the plugs were changed, new coil pack, new injector. Previous owner gave up on the problems. The codes I read are P301, P302, P303 and P325. The Misfires are the big concern. At idle there is a ‘miss’ most of the time. When I turn on the ac, the idle drops when cold and the engine runs rougher. Possibly suggesting an intake leak. The engine revs fine in neutral, but bogs down under a load. The CEL is on, however under acceleration it flashes. Sometimes the power is almost completely gone, but still idles fine. Will the knock sensor affect the ignition to create a misfire situation? Will a failed EGR cause the misfire? I suspect there are at least two separate issues. I live no where near a Subie dealer, any ideas will be of great help.

  122. Serena,

    Are you saying the check engine light has been on every instance of driving since 2006, the Catalyst is covered under the 8 year 80k federal emissions warranty, so unless the diagnoses occurred after 80k it should be covered, the Catalyst will not
    cause he hesitation though.


  123. Hi John,

    You most likely have valves hanging up in the guides, you can try a fuel induction service and maybe an oil flush, both of these need to be done with caution at 280k, if that doesnt work you may need a valve job to cure the sticky valves.

    If you suspect the EGR, all you have to do is disable the EGR by disconnecting and plugging off the vacuum line to it , you may than set a PO400.


  124. Hi all:

    A week ago I inadvertently forgot to replace my gas cap after refueling my 2000 Impreza 2.5RS coupe. I drove 150 miles over the course of two days until the third day when the yellow check engine light came on. I checked the gas flap and realized the mistake I had made. Since I was far from an auto parts store and it was a weekend, I had to put on another 120 or so miles with the check engine light constantly on. I purchased a new gas cap, refueled the car, and installed the new gas cap. I’ve put on about 100 miles over the past four days since then and the check engine light is still constantly on. The car starts up and runs “normally” except that I’ve notice a burning type of smell during these past four days. The smell, which I don’t ever recall smelling, before seems to be most noticeable near the driver’s side rear wheel. I haven’t had the rear disc brake pads replaced (the car has 137,000 miles on it) in several years, if at all. Could it be the rear discs/pads I’m smelling? I’m concerned too about when the check engine light will go off and whether I might have somehow damaged something by driving essentially five days (approximately 350 miles total) without a gas cap. Help!

  125. Hi Rudy,

    Some of the aftermarket gas caps leave a lot to be desired.

    Having said that, with out a simple code scan we don’t know that you have a P0440 set which would be the most common code set for a loose or misplaced gas cap.

    After resetting a loose gas cap, the computer must see Evaporative or fuel tank pressure before clearing the code and turning off the light.

    Not sure what to say about the burning smell.

    I would have the car scanned and go from there.


  126. Hey. I just got a 1990 Subaru Loyale, and the check engine light was off. But once i popped the hood open and looked inside, there was a wire that wasn’t attached to the other half, so i connected them and now my check engine light is flashing.

    The wire I hooked up was black with a red stripe on it, and it had a green cap on the male and female connection site. What was it that i connected?!


  127. Jon,

    That is called the D check connector and it is To be left disconnected. The D check mode is also known as Dealer Check Mode, and is used in conjunction with the Subaru Select Monitor for Diagnostics.


  128. Hey, I have an 05 Impreza RS and monday I had my headers installed and its been driving great. On Wednesday night I put a fuel cleaner in my tank when I had about a quarter tank left and filled with premium as always. Yesterday night (thursday) while driving my check engine light came on (steady) and my cruise control light is flashing. Im not noticing it to be driving differently but it wont go off. Do you have any ideas? Im wondering if its the fuel cleaner?? Thanks!!

  129. Heidi,

    I would start with checking the gas cap, it’s possible that you didn’t get it tight, try tightening it, if it moves at all before making the clicking noise it wasn’t sealed, and yes this can cause the check engine light to come on.

    If and this is a big one, IF it was loose that may have been the cause, if it was tight then it was something else.

    Now if the gas cap was loose tightening it is just one part, it will either take a few drive cycles for the light to go off or it can be cleared with a Scan tool.

    If the gas cap is tight you have something else going on, and all 2005 and newer Subaru vehicles will always have a flashing cruise control light and disabled cruise control system anytime the check engine light is on.


  130. I have a 2002 Forester with 170,000 miles on it. I purchased it new and the “Check Engine” light has been on since the first year. Occasionally it goes off for a few weeks and then comes back again. Subaru has checked and re-set it many times and replaced the gas cap, but the light always comes back on. It will surely fail the upcoming NJ state inspection. I wish there was a solution to this problem. Otherwise, I love the car!

  131. Hello C,

    I guess I want to start with saying I have answered this exact question above many times on this page, and I would encourage you to take a minute or several and read some of the posts and my replies.

    To recap, Every time the check engine light comes on it sets a code, THE CODE is what is important not the light. You the driver only see the light and no, every time the light comes on it doesn’t mean the gas cap is loose, but the gas cap being loose is one of many possibilities.

    On your paper work listed the Dealer is required to note the code number such as “po440 Evaporative emissions system leak”

    The last thing that should ever happen is a check and reset, without a diagnosis.

    The next time the light comes on find out what code is set, and have that system evaluated.

    There is an easy solution, but it needs to be evaluated by a pro and not reset, but it will cost money to truly take care of it.


  132. Dear Justin,
    What a fantastic website. Congratulations on your expertise.
    Now, I wouldn’t be posting here if I did not have a problem…
    I own a ’98 (outgoing model, european version) Legacy Wagon, 2.0 non-turbo, manual. Engine code EJ20. It has 270.000km’s, that’s about 170000 miles on it.
    The problem I’ve been having is this: the engine functions perfectly, except for the following behavior. When I take my foot off the accelerator (with the clutch pushed down) after driving along at 3000-4000 rpm for a while, the revs would fall to below the idle rpm’s and then pick back up to idle. Sometimes, though, it would just stall. Also, sometimes the CE light comes on. I’ve taken the car to a very highly rated Subaru dealership (they do maintenance and tuning on all STI’s and the like for our country), they checked out everything they could think of but got no results. Valves have been checked and their tolerance adjusted. As I also run it on LPG, I took it to a LPG expert. He told me the throttle position sensor gave off a wrong voltage. I had that replaced, now it does not stall anymore, but the CE light still lights up intermittently in situations as described above. If I then hold down the clutch, lift off the accelerator the light goes off. It seems to come on when I try accelerating from low revs in a high gear. Subaru can’t read out any error codes, as there aren’t any (!).
    Any guesses?
    Sincerely, Herman

  133. Hello Herman,

    No Guesses, But I am not sure what kind of a emission system they run in your part of the world either, in the U.S. its not possible to set a check engine light and not set a code, the code may disappear after a few drive cycles and no fault seen. Now the older models, and I suspect some of the Later models in other countries could have a light come on and the code not stay in memory, meaning if you didn’t scan it as the check engine light was on, there is a chance you would never recover the code.

    My suggestion is that someone with a Subaru Select Monitor or the like, needs to drive it the way you are until the symptoms can be reproduced. There is just no other way to get to the bottom of it I am afraid.


  134. I had the 02 sensor replaced (per subaru’s recommendation) twice now and the CEL continues to plague my car. With the “cruise control” flashing (and disabled) , I am beyond frustrated. The last Subaru dealership refunded my money as I pitched such a fit over them being unable to correct the problem. I was a huge fan of Subarus til now, and after reading all these issues, I am done with subaru for good. I will not buy another one. This many people having issues with CEL,,, has to be something more to it than just every day wear and tear.

  135. Hello Gborto, and future readers of this post

    I am going to start and end my comments about the above with the following statement.

    If you really take the time to read posts on this website you will see a common theme, no one ever starts out a negative post about their car by stating “I have had a long standing relation ship with a Independent Subaru repair shop that cant fix my car”

    Now that that is out of the way.

    Wow, sounds like you have had a rough time getting a real evaluation and repair, while I am sorry you have had a frustrating experience, I can tell you that you are angry for the wrong reasons and I doubt you have called Subaru, the Dealership you are taking you car to is not Subaru of America, they are merely a franchise like a Mcdonalds. If you have bad service at the golden arches, and dont get anywhere at the store level, and feel very passionately you deserve better, most will call corporate, or consumer relations or the like, the same goes with any car you own. If you dont go that step, there is no way For Subaru to know you are having any difficulties and you are unfairly bashing them with out cause or giving the company Subaru a chance to make it right. Again the Dealer is not Subaru, they are a franchised seller of Subaru vehicles, authorized parts and service center and a for profit business. The amount of profit, is going to directly affect the level of service you will obtain.

    I wasn’t sure after reading your comments, that I wanted to allow it on the site, but after I considered it further I realized its another good opportunity to try and teach you and others about your car. You will no doubt not like all that I have to say, and I ask that you try not to take it personal, as I am trying to teach you and other readers, how to navigate through service dilemmas with the least amount of frustrations in my opinion.

    You are right though, the check engine light is something more than normal wear and tear. The (broken record here) check engine light can come on for a thousand different reasons, sometimes its simple straight forward and caused by a loose gas cap, sometimes its caused by a rodent that chewed a portion of wire you cant see without removing the entire dashboard, sometimes its a unintended consequence of the quest for lower vehicle emissions, something learned after the newer model has been out for a few years and a software update is needed to correct a “learned condition”.

    I will also comment that there is far to much technology crammed into cars right now, look no further than all of Toyota’s problems as of late as proof of this, no the floor mat isn’t the problem. When your Pc or Mac does something buggy related to data inputs, it doesn’t affect your ability to get to work or pick up the kids from school, but in your car it does. If you are going to tell me that your computer has only had one or 2 bugs in 5 years I will say that is just truly amazing but unrealistic in a computer that drives down the road, subject to temperature, humidity, vibration, corrosion, rodents, abuse, neglect, stupidity, design flaws, and I can go on for an hour here.

    First of all the check engine light and the codes that set the check engine light after 1996 are not Subaru’s problems they are every car makers problems. Any and every car has the potential for all of the same issues and yes starting in 2005 if the check engine light is on there is no cruise control function plus the cruise light will flash at you, and the reason for that is so that all of the drivers that go around with a check engine light on because they dont “think” they need to resolve it will take it just a little more seriously. Wait until you see what the current models do when a check engine light comes on, its not the car companies, its he EPA, and the Department of Ecology, and the pursuit of cleaner air that makes the rules. Google or Bing “AB 32” and look for your self what is coming. Its not as exciting as the new Iphone, or as horrific as the oil spill in the Gulf so it obtains no real media time. For every Subaru owner that is mad at a check engine light there are 5 Toyota and Ford owners mad for the same reasons…

    Newer vehicles will be exempt from emissions testing, because you will have a real tough time of driving them if they have a malfunctioning emissions control device. The days of a driver ignoring a check engine light, or a service provider not accurately diagnosing and making repairs is slowly coming to an end, but as with everything else, it will come at a cost. I have been saying this for years, but the newer the car the more it costs to buy, own and maintain. You either have a car payment every month for the rest of your life, or you keep a car past the payment period and the repairs and maintenance come in to play, there is no money in it for the car makers to make cars that dont need maintenance and repairs, thus the reason for the large service department at every Dealership regardless of the car line.

    We had to implement tire pressure monitoring systems because drivers can no longer be bothered to check the tire pressure in their car, this added almost $2000.00 to the cost of the car, and another light that can come, and a system to be checked even if the tires are not low, which is a new system that has issues, and if not addressed wont alert you if there is a real problem. A system that we seemed to not need from 1927 until 2007. The reason for the system is that it was revealed in a legal proceeding that a car with low or over inflated tires could be unstable. So big brother came to our rescue, because a portion of the population couldn’t check the tire pressure in the car forced a system on us. Because not every one will repair a faulty emissions system, or take it to the right service provider the rules are changing yet again.

    New cars dont even have throttle cables, because more precise fuel management and lower tail pipe emissions can be obtained with an electric motor on the throttle assembly, but it can also cause the engine to accelerate with out you wanting it to.

    Now when it comes to the systems pertaining to the check engine light on a 2005 and newer “any car you drive” things are even more “out of hand”. Modern cars are complicated, and drivers dont often understand, care or have the time too.

    The following statement “This many people having issues with CEL,,, has to be something more to it than just every day wear and tear” , is just real troubling to me, its frustrating to the driver of a car to have a problem go unresolved, especially after its been paid for, and its emotionally upsetting to go with out your primary method of transportation. But you are in charge, its your car. If you have an unsatisfactory experience at one service provider go somewhere else. But do so knowing its going to cost money, and it may not be simple, the fact that one provider already failed for what ever reason is proof to either its complicated, they are not qualified, there has been a communication issue, or the customer is difficult. A check engine light is just not the same with being unhappy with a tires performance.

    The only thing you mention is the CEL light coming on, but not the code number, only that the 02 sensors were replaced twice. The same ones?, depending on the year you may have 4 02 sensors, and most 2005 need a firm ware re flash in correlation to the 02 sensor replacement. For you and all others who read, know the code that was set, not that the light is on. The light is an indication that there is a code set, ask for the code, and put pressure on congress to make it so car makers have to have a system in place to read out codes on the dash board not just a light. That way you dont make an appointment at a Dealership for a loose gas cap.

    The single biggest obstacle in diagnosing and repairing a modern vehicle is Money!!! The second is Money , and the third is Time & Money.

    Auto repair is NOT an exact science, when it comes to diagnosing a check engine light, sometimes its very simple and sometimes is very difficult, just like modern medicine, sometimes the diagnoses is clear and accurate , and sometimes it takes several visits to the doctor, and several tests to get to the bottom of it.

    The media does a fair job of informing us about insurance companies making it hard for doctors to order expensive tests right off the bat right?

    But are you aware that all of the same things are in place during diagnoses of your car? During warranty the Car maker, regardless of who made it, makes it almost impossible to get good service due to the amount of money they will pay vs the amount of time a tech will spend trying to figure it out, let alone not pay for a part that didn’t fix it. If you are a tech being paid by the job to make a repair, and if you are wrong you dont get paid, and you have a family to feed are you going to spend much time on it? I have worked at a dealership during a warranty audit, and watched the service manager pack up his desk while the owner of the dealership wrote a 6 figure check to the car maker. The reason? To many grey area repairs covered under warranty some no doubt for questionable repairs but some in the pursuit of trying to provide good service to the driver of the car.

    When the car is out of warranty the time and money obstacle is the customer, only wanting to pay for needed repairs, and in many cases not wanting to pay for diagnoses because they think Auto Zone can do it for free. Every situation is different, if you have a good relationship with the service provider you should get FAIR service if you dont have a go to guy, dont expect it. In as much as they may not have earned your trust, you have not earned any ” free time”.

    Its a process of elimination by testing suspected systems and components, and sometimes the only way to rule out a component is to install a new one. But guess what there is no subsidy, no insurance, only real costs for parts and labor. If a part is put in, and it doesn’t correct the symptom you dont want to pay for it, even if during testing it was found to be marginal and was the most likely suspect, and diagnoses really cant continue until it is ruled out as it is the most logical next step.

    I have yet to have a customer not be concerned about how much it will cost “just to figure out what is wrong” If at the service counter we instead told you it could take us up to 8 hours to figure it out most would laugh or just go somewhere else, it doesn’t mean that every car takes that long but once a week on average we get one that throughs us for a loop and changes the whole week for us in a very negative way.

    I really cant speak to the specifics of what has transpired with your car, but to service provider a customer that will “pitch a fit” or cause pressure is better left to go somewhere else, to a customer a service provider that cant correct the problem in what is conceived as a reasonable amount of time for a reasonable amount of money are idiots. Neither is fair or always accurate.

    At our shop we pride ourselves on getting to the bottom of every situation, I have never not repaired a car unless the customer did not want to pursue the course of action I was suggesting. If I have had a good long standing relation ship with a customer I want to get to the bottom of a complex issue for them because its our job, and I know that time loss on this situation will most likely be made back up in future business and potential referrals from this customer. If it is a first time customer fed up at a Dealer service department (which is the last place you should ever take your car for something like this once its out of warranty) its an opportunity for us to shine and hopefully EARN a new customer.

    Its the drivers one who take it to the $19.99 oil changes places, and are stabbed for $200.00 in filters and flushes with the take it to the Dealer for a repair or diagnoses that have the most frustrations.

    I dont know the circumstances of your dilema, but I cringe at the pitch a fit statement.

    As in may cases it will take me 5 years to be right, but if you bail on the car you have now, and buy something else there is a very good possibility the same thing will happen to you again, some things go smoothly and some do not, some drivers are less able to deal with multiple visits to a service center for what is perceived as the same thing some cant make the time for service at all so they get very little of it. We just dont know what this years model will be like for years to come, I highly doubt many would have bought the Previa had they known that in a few years there may be the recently reported issues..

    If you really take the time to read posts on this website you will see a common theme, no one ever starts out a negative post about their car by stating “I have had a long standing relation ship with a Independent Subaru repair shop that cant fix my car”

    If you find the us near you, and build a relationship you will be happier about car care. If there is no Independent Subaru Shop near you that makes it much tougher to get good results. You may be stuck with the Dealer, or just a good independent shop, and I prefer the later.

    Hope this helps all who read it


    1. Hi Justin,

      On behalf of our family, thank you for the tremendous time and effort that you put into what can only be considered a public service. I read the comments to here and learned a lot.

      One thing you alluded to above is the necessity to update the code in the car’s computer because of newer firmware. Is this possible? If so, can you tell us how, please (we have a ’99 Forester with ~160K miles on it that we’d like to keep forever).

      Kindest regards,

      1. Tom,

        Firm ware can only be updated with the Subaru Select monitor II and III.

        There are re-flashes that can in fact correct a check engine light by changing the parameters with in the programming to accept different readings or ignore others.


    2. I just wanted to say thank you! You are extremely informative and it’s so nice to find so much information all in one spot. I live in Bellevue and will definitely be coming to your shop if I have any additional problems in the future.
      Thanks again.

  136. A few years ago we posted a question on a forum (cant remember which one, and old links no longer work) about a 1996 Subaru Legacy wagon engine problem, and got an answer that the 1996 Legacy 4cyl engine, was a ‘lemon’ year for Subaru.
    Apparently, there was a ‘valve’ problem, just this particular year, that caused the ‘check engine’ light to come on and there was no fix, because any fix was to replace the parts with the same parts as new, and so the problem would still be there.
    The problem was such that it could run forever, with the engine light on, or the engine could die tomorrow.
    Does anyone have any info about such a problem ?
    Thanks much.

  137. Hello AKM,

    Not sure about the missing post.

    The 1996 was not a lemon year by any stretch of the imagination.

    Unfortunately advice on many of the Forums from drivers is inaccurate, just because they weren’t able to fix it, doesn’t mean it cant be fixed, I have yet to encounter a Subaru we couldn’t repair.

    Its kind like me saying that installing crown molding is impossible because I cant get it to look right, whereas a professional can come in and make it look great.

    The average Home gamer knows the basics, some know more than the basics, but the average guy doesn’t know nearly as much as a Journey Level Technician.

    The average Journey Level Technician has zero to do with the Forums.

    The 1995 to 1998 single port 2.2l Legacy could develop an exhaust valve guide that can shift or “drop” causing a intermittent misfire as a result of the valve hanging open monetarily at higher speeds.

    The problem is easily repaired by a qualified machinist or by installing a set of Subaru Re manufactured cylinder heads. But it is expensive to do so.

    Check engine lights go unrepaired when the owner takes the car to the wrong service department, meaning they dont know how to fix it, or the customer doesn’t want to spend the money to repair it. There are no other reasons.

    It would be illegal for Subaru or any other car maker after 1996 to have a uncorrectable condition resulting in a check engine light.

    Look to the vehicle emissions laws pertaining to OBDII, and all that have been passed since.


  138. Hi Justin,

    I have a 2004 forester XT with about 100k on it. I was running fine until I was accelerating yesterday when the Check engine light came on and it started misfiring. The check engine light then started flashing, I tried to read the codes with an inexpensive reader I have but I was unable to retrieve any. The plugs where just changed about 10k miles ago. I had it towed to the deal and am waiting to hear what they find. Any ideas?

  139. Hi Justin,
    The battery in my 2006 Subaru Legacy 2.5i Limited was replaced today. When the car was restarted the it idled very low. On the way home the check engine light and blinking cruise control came on. Is this normal after having a battery changed? Thanks for your input!

  140. Hi Justin,
    I have a 2006 Subaru Legacy 2.5i Limited. The battery was replaced today, and upon restarting the engine idled very low, then check engine light came on along with the flashing cruise control light. Is this normal after a battery replacement? Thanks for your advice.

  141. Hi Justin,

    Got a weird one here. I have an ’02 WRX that was throwing a Cylinder 1 misfire. I’ve since replaced the plugs and when I did I flipped the coil packs on it. Front went to back and back up to the front but they stayed on there own sides(i.e. driver side coil packs stayed on driver side). Driving it a bit more after doing that now throws Cylinder 2, 3 and 4 misfire but 1 is ok now apparently. What the heck is going on? I really don’t want to drop a chunk of money on coil packs if that’s what’s not wrong but if it is that’s fine. What do you think? Thanks.

  142. Hi Chris,

    When there is a misfire you must test until you find the cause. If you moved the # 1 coil to # 3 Cylinder and the misfire changed to # 3, I would suspect a coil is possible, not very common but possible.

    The fact that you created 2 more misfires may be related to the parts you used?

    You should only use the factory NGK Platinum plugs and nothing else.


  143. I did use NGK Platinums. No other new parts were added. I just moved those coil packs around as mentioned and now the other three cylinders are misfiring instead of the original one that was and no longer is.

  144. Your site was a lifesaver! I have 1995 Legacy wagon with just over 180,000 miles on it. Earlier this year I had a much needed replacement of muffler and tailpipe. At that time, I was told that my cat was okay and didn’t need to be replaced. Of course, in the beginning of June (the month my Pa inspection was due), my CEL went on. I did the usual with the gas cap, but no luck. I was going on a long trip and had it in (not to a dealer) to have belts, fluids, tires, etc checked. I always do this when I’m going to be driving a distance of more than 500 miles. They told me they couldn’t inspect it, as it would not pass emissions because of the CEL. They also said that I DID need a cat converter. As far as I know, they didn’t test anything. I found your site when I was looking for some guidance and I’m so glad I did! I went to an Auto Zone where they tested it and found that it was a code PO420, so I knew it was an emissions problem and not something with the engine. I was able to find a gas station with no ethanol in their gas, and did two fill ups before I went on my trip. I wasn’t sure what would count as a drive cycle, but I was delighted to find that my CEL went off about halfway through my week away. At the end of June, I went back for my inspection and passed with no problem. If I hadn’t had all the information on your site, I probably would have had the cat replaced, at great expense and inconvenience, before I started the trip. I really love my Subaru, which I bought with 115,000 miles on it. I can’t imagine getting any other car in the future.

  145. Hi Justin
    I have a 2000 SOB Limited. About a year ago a ran it into a ditch. The engine was submerged and water reached the cabin’s floor boards. My insurance company paid to have the vehicle repaired at a local Subaru dealer here in Orlando FL. Since then, I have taken the car back to the dealer three times. The first time I took the vehicle back it was for a faulty oxygen sensor. The second time a broken CV joint, and the third was an intermittent CEL that was cleared by the technicians without actually doing any work. Recently, I had to replace the alternator because it was overcharging the battery. I think that since being under water, the vehicle’s electricalelectronic system has been compromised. To me that means that CELs and electrical problems will continue to creep up making me a cash cow for the dealer. My question is: What reasonable argument can make to have the insurance company total the vehicle and issue a check? Currently the CEL is on and an OBD II analysis indicate a PO328 code. Will this ever stop?


  146. Octavio,

    So usually in a water damaged car it’s found that corrosion in the wiring occurs this can cause issues but will eventually be traced out by a good tech if its causing a problem

    I know this isn’t what you want to here but everything you have laid out is normal we replace knock sensors 02 sensors and alternators weekly

    It’s all normal stuff to do on a 10 year old car even if it never went into a ditch


  147. I have a subaru imprenza 2.5 RS had a check engin saying knock sensor was failing. about 200 miles later tried to start the car and it started but RPM’s droped and the car chocked and died. the starter is working but the engine wont kick over. i have now replaced the knock sensor and the fuel filter. the car still wont start. have tried jumping the car from cables but still no luck

  148. Thank you for this post. I’ve been dealing with this/similar problem in my 2006 Impreza. The check engine light came on the first time when I failed to tighten my gas cap properly. It has appeared two more times, in the same situation: a low tank of gas taking the same turn into my neighborhood. The CE light comes on, and my Cruise Control Indicator light appears and begins blinking.

  149. Also, how do I find someone as qualified as you in my area (Fort Worth, TX)? My car is out of warranty, and I would like to find a shop I can trust to fix the correct problem, uh, correctly.

  150. I have a 2002 Legacy with a check engine light on. My local mechanic said it was the catalytic converter which he replaced. We drove it about 20 miles and the light came on again. He changed two sensors and after 20 miles the light came on again. He replaced the catalytic converter and within 10 miles the light was back on. He know says that we must have a head gasket leak. The head gasket had been replace about 20,000 miles ago and I really don’t want to do that again since I’m wondering if I really needed the whole exhaust system at this point. Any suggestions?

  151. Justin,

    I came across your very informative website when I was searching for information about the flashing CEL in my 2001 Subaru Outback wagon. I was on a trip this past Friday when the CEL came on just after I had filled up with gas. I stopped and checked the gas cap, and determined that it was on tight. With the CEL on steady but not flashing, I drove 75 miles, almost to my destination, stopping at my mechanic’s shop to make an appointment to have the CEL checked and the oil changed this coming Tuesday. I then drove the rest of the way home–about eight miles. Then yesterday (Saturday) when I started up the engine for the first time since the Friday trip, the CEL began flashing! The engine was also idling roughly, something I had never noticed in this wagon. I immediately shut the engine off and have not driven it since. The mechanic’s shop is approximately eight miles away, and three of those miles are across a bridge–a long bridge! Should I be concerned about driving the wagon that far with the CEL flashing? I could have it towed or hauled instead.

  152. Hi Cheryl,

    You can try car talk’s website, or ask fellow Subaru owners who services their Subaru.

    Without knowing code numbers its just not possible to know the cause of the check engine light.


  153. Hi Sharon,

    “My local mechanic said it was the catalytic converter which he replaced. We drove it about 20 miles and the light came on again. He changed two sensors and after 20 miles the light came on again. He replaced the catalytic converter and within 10 miles the light was back on. He know says that we must have a head gasket leak. The head gasket had been replace about 20,000 miles ago and I really don’t want to do that again since I’m wondering if I really needed the whole exhaust system at this point. Any suggestions?”

    You havent listed any codes at all so I must assume it had a po420 Catalyst below threshold must have been set? But from the sounds of it there has been no real testing, or the shop isn’t communicating their plan of attack very well ?

    My guess is that the repairs were made with cheap aftermarket parts which in some cases will not satisfy the factory programing for oxygen level increases within the exhaust system, I would start by getting the answer to the following questions.

    1. What code or codes are set
    2 What tests were done
    3. What is the Diagnoses
    4. What kind of parts are being used
    5. Were there signs of coolant on the 02 sensors?
    6. Is there a history of coolant loss?

    Hope this helps


  154. Hi Patricia,

    I would be concerned about driving it with a flashing check engine light as a flashing check engine light means a cylinder misfire, and a misfire can damage the catalyst and in some cases cause engine damage as well.

    You also high light what is the matter with the whole check engine light thing, once it was a gas cap and no big deal, so the next time we immediately think ” i know this” but in reality the light should be replaced with a “code display” so drivers would have a better sense of when its ok to procede with the trip or get in to the shop.

    Hope this helps


  155. Thanks for the advice, Justin! I am now convinced that I should have the wagon towed or hauled the eight miles to the mechanic’s shop. I had the catalytic converter replaced two years ago by my Subaru dealer’s service department–many $$$. I don’t want to do that again if I can avoid it!

    I agree about the need for a code display–the CEL, whether steady or flashing, doesn’t give a driver enough information to make an informed decision.

  156. I have a 1999 IMpreza OUtback that Failed Smog Emissions. The Mechanics dont know whats the problem. There is no CEL on and the Car’s Emissions are fine until the Radiator Cooling fans comes on. As soon as the fans comes on, Emissions goes up by 20%. PLease if you know whats causing this it would really help. Thanks.

  157. Hi Justin,

    I recently bought a 2006 Subaru Legacy GT with around 60,000 miles on it. About a month after I bought it I had the oil changed and after-market exhaust put on it and had the check engine light come on and the cruise control stop working. When I took it to the dealership they said it was because of the after-market exhaust and that they didnt have the computer system to fix it. Can your shop fix it or can you reccommend somewhere close to the Kitsap County area? Is my cruise control not working because of the same reason check engine light is on and is there anything I can do to fix the cruise control??


  158. Hi Blong?

    Id need to see the car to diagnose it, Im curious as to what state you are in as 1996 and newer vehicles in most states dont require a tail pipe test as part of OBD II.


  159. Hi Meghan,

    Yes we can fix it, pretty typical actually there are 2 different ways to approach it, the best is to buy an aftermarket programmer such as the Cobb Access port.

    You can call the shop at 425 828 3600, ask for Ryan he is our performance expert.



  160. HI Justin,
    I have a 2002 Subaru Outback Wagon 4 cyl. Around 6 months ago the check engine light came and stayed on. I had the codes read and the mechanic said it read “emission” and that I need a catalytic converter. He cleared the code and told me I would have to repair it before my smog test which is due in Nov. Since then, the CEL would very occasionally come on after driving several continuous hours but then would go off after turning off the car, not reappearing the next time the car was driven. Recently, when the car got warmed up, it would start hesitating badly and back firing. I had a 1/2 tank gas, filled it and added injector cleaner, then the car ran fine until I got down to 1/2 tank gas. The car then repeated hesitating and backfiring after it warmed up – CEL never came on! I had a “mechanic” look at the car and he said there was a vacuum leak he claimed to repair but upon driving, the bucking and hesitation returned when the car warmed up (took around 1-2 miles of driving). Please, what do you think is going on here? Also, the “mechanic” said there were no codes stored from the CEL events. Thank you

  161. whenever i have gas in my tank my check engine light comes on, but whenever my gas light comes on my check engine light turns off…

    help me please!

  162. Hi Carolyn,

    Really you need to take the car to a Subaru Technician near you. I can speculate for an hour on all of the might be’s.

    There is no Such code as “emission”, all codes have a number.

    The level of the gas tank and the bucking dont have anything to do with each other.

    Most likely there is a sensor out of range, it will take some testing by a Subaru Expert.


  163. Hi Justin….original owner Suby Outback Limited 2001, 52K miles well serviced, had clutch done @ 50K first time ever to recharge the air conditioning, started noticing an intermmittent humming sound like blowing into an empty bottle and a click click… when turning on the ac sound coming from behind the glove compartment, thinking I needed to replace the cabin filters, I decided to take apart the glove box to get to it, to my surprise it did not have the filters, I vacuum cleaned the area which it had debris, dirt, leaves. I got the filters and put it back. Sound continues when ac on is set at #4 blowing control high as I drive
    (5 speed manual trans) it kind of decreases speed off and on repeatedly street driving, and also at freeway speeds. The intermittent noise and the decreasing speed off and on happens simultaneously. Temps. here are in the 100’s so we just turn the air off and it works just fine. Thought could be the belts, so I sprayed more than enough silicone on them…….no luck HELP! thanx a lot.

  164. Hey Justin?
    Your site is sweet! Thanks for all the info. 2 ?’s:

    Have a 2005 Subaru 2.5x with A CEL on every 150 miles or so. Brought it in today to a local mechanic (not dealer) and he said the rear 02 sensor was reading “lean” ie: not reading enough exhaust to get a good reading. Said that the car’s exhaust was leaking in th “y pipe” and that would cost $700 dollars to fix…ie special order parts and whatnot. I can’t hear an exhaust leak, but rear 02 sensor is good. Is this a reasonable price to fix this exhaust and is it possible for me to change the pipes myself. (Are they just a bolt-on exhaust part that I can buy over internet etc.)? By the way, what is the “y pipe”? Is it coming straight off the exhaust manifold or is it the section of pipe where the two sides connect before the cat? I’ve look under the car numerous times trying to hear/detect any leaks but to no avail. Please give me a nod in the right direction. Your input is much appreciated! Thanks, Kristian

  165. 1 More question:

    What’s your opinion of “Steelseal”?

    I’ve heard it works? Are there any ill side effects? Thanks again,

  166. ED

    While thats nothing typical I would start with looking at the Fan relay as its in use in a different way for speed 4 only, and the rest of the time the speed is controlled by the Ballast resister for the fan motor.


  167. Hi Kristian

    I am not a Steel Seal Fan, I believe in repairing what is wrong properly and moving on, I also wouldn’t fix a leaky roof with a tarp either.

    As far as the Exhaust terms, you dont really have a true Y pipe on a 2005. You have a header pipe, than the Catalyst, Midpipe and lastly the Muffler.

    I would buy only Subaru Parts nothing aftermarket, if buying that over the internet is feasible than yes.

    Most Subaru Exhaust parts are bolt together.


  168. 2003 Subaru Outback Impreza
    123,000 MI

    OBD|| read codes- P0031 (bank 1 sens. 1)
    – P0037 (low bank 1 sens. 2)

    I changed the fuel/air ratio sensor (pre- cat) and the O2 sensor (after cat)
    -Using OE Denso Replacements.

    Cleared the codes, drove it and now the same codes are back? It would seem that the Catlytic Converter is plugged up, but I am running out of money…

    Any suggestions toward “cleaning out the CAT”, or will replacing it only be just as much of a gamble as the previous sensors?

    I also, was unable to pass smog in WA, and was told the cars computer had no stored TRIP “Freeze Frames”, and this was all prior to replacing the sensors and clearing the computer’s memory!

    I wish all cars were like my 69 Maverick, simple and easy to spot necessary repairs!

  169. Hi Mark,

    Some of this isn’t really adding up. Unless someone has cleared memory thus resetting the emissions monitors, there is no reason the car cant be tested.

    The fact that you are able to pull codes out is proof that most of the monitors are at ready status.

    A Subaru Select Monitor would revel which monitors are ready and which are not.

    There are some things you can do yourself such as install the parts, but to evaluate what is actually wrong most likely a Pro will need to get involved or it may just lead to more of the wrong results.

    I know you are looking for some direction, but without viewing the car there is just no way to know, I will share however that with fault codes showing for both front and rear 02 sensors the last thing I would suspect is that both 02 sensors had failed.


  170. Thanks for the feedback! I did notice today, that when I tried to blow some of the carbon build up out of the CAT, that dust was actually pushing out from the side wall of the CAT… It must be toast as this should not happen right?

    As for the Smog test, I had not cleared the codes, in fact, they also gave me the same feedback on the failed printout. But still told me they could not complete the test? Doesn’t make much sense that they can’t even test the actual emissions, and let me worry about the fault codes..

    Thanks again,


  171. I just moved to portland, OR and am wondering if you know of any good independent subaru mechanics in Portland?? Any help would be great!

  172. For some reason my 2006 started sputtering. I replaced the spark plugs of which i found to be the problem. But now since I had to take out the battery and reset the check engine light, the car idols way to low and almost shuts off if i am coming to a stop. Any suggestions or ways to correct the problem.

  173. I was driving my automatic 2001 2.5 subaru outback home and was getting what sounded like an intermittant relay chattering from under the dash. The revs suddenly went a bit wild and stalled at 40mph. i slipped into neutral and coasted to a stop. When i tried to start the car it would turn over, catch the stall. Tried to start for the next 20 mins and much the same. After walking a while to get some signal for my phone to get help, i returned to the car after an hour and the car started with no problems and engaged gears. I then drove it a couple of miles to a car park. During the problem i did not get an check engine light but have have noticed the ‘hold’ lamp does not light when turning the ignition on, however if i select it on the gearbox it lights up, that is something new.

    Any thoughts appreciated

  174. Phil,

    Sorry, and this does come up a lot, but I live in my little corner of the World, and just don’t know all the shops out there and what they are are more importantly are capable of.


  175. Daniel,

    Im sure it has corrected it self by now.

    Not sure why you disconnected the battery, but try not to do that unless you are replacing it.

    There is never any reason to disconnect the battery if you fix the problem all you have to do is a Drive cycle.


  176. Hi, this is about our 2005 legacy wagon (non turbo).
    Had a body shop do work on driver’s door, when we picked it up, they had created a short circuit (dome, dash indicator for doors, radio and clock out). They fixed the short. All’s well, right? Unsure…
    Now CEL flashes. Self-diagnostic OBCII codes 0101 0102 0108. Also rough idle, some stalling. Was going to replace the MAF; could it be remaining short circuit from body work or do you think the MAF failed unrelated to short (or could it be a vacuum or other leak in the intake manifold)? Disconnected batter (pos & neg) and drained capacitors with brake pedal… Any ideas appreciated.

  177. Hi Ken,

    Really the last thing you want to do in the course of diagnoses is to clear memory and reset the monitors.

    So I am thinking there is a piece of info missing like how did the door get damaged?

    Was it in an accident, and if so was there more damaged in the accident than just the door?

    If you don’t have the ability to diagnose the codes. You may want to consider getting a Subaru guy involved for at least the diagnoses.

    Did the car run just fine when dropped off for the door repair?

    I would really hate to hear about you spending your money on replacing parts that arent needed as part of your diagnoses.

    Testing the Map is where you should start if you suspect it.

    In the “normal course of repair” there really should be no reason that door work creates another issue, but I have no idea what was done, or why it was done.


  178. I just wanted to say thank you for all the info you’ve posted. I’m not in the Seattle area, but I would definitely be a customer if I did. I’m certain I’m not the only “lurker” that benefits from the information you’ve provided.

    Thanks again.

  179. Had the same problem now with subaru p1! GARAGe is baffled by it! They have had it a year. They rewiresd it changed all sensors! Now it passed mot so nothing wrong with emissions. Also running fine. Now i do pick up the car thinking its just a design fault! OR will it blow engine again?? BTW car oes not tell computer any codes??? and its flashing chec engine light!

  180. Natasha,

    Really none of you have posted makes much sense to me.

    Its possible that the shop may have inadvertently left the vehicle in D check mode and that could explain a flashing check engine light, or there is something more serious going on.

    Modern cars dont get rewired, Modern cars dont need to have all sensors replaced.

    It sounds to me like there is some sort of understanding gap, some communication error. Not understanding can make things very frustrating.

    No professional shop would keep a car for a year where I am from.

    You need to find a Subaru expert with a good reputation, until you do that you may continue to have unsatisfactory results.


  181. I have 2002 Subaru legacy, my exhaust is giving really high smell of carbon and also the inside of the exhaust from the back is really black but no black or white smoke coming from there, when I turn the engine on and leave it to warm up water drips from the exhaust but also very high smell of carbon, also when I press on the gas to move while the car is not moving, it gives a feeling that I will turn off and its not smooth, a feeling of a shake like its turning off then it moves and while moving speeding or not there are no problems at all, I took it to several work shops and they are all suggesting to clean the injection and change the spark plugs, change the spark plugs wires, I did all of that, but still im having the same issue, I don’t know what could be the problem, the check engine light is not on, everything else seems fine, took it to almost everywhere no one knows what causes this, please help. thanks

  182. Hi Justin,
    Thanks for doing what you do man.
    I have a 2008 outback 2.5L. 45000 miles. Had a front end accident, replaced right front fender and front end. Picked up the car drove 4 miles to get a sticker at the dealer (failed for front brakes)left dealer and got cel/airbag/low tire pressure/flashing cruise lights on within 2 miles. cel on constant. DTC P0028. Your thoughts?

  183. Hello, Justin.

    I have a 1999 Subaru Forester. Today it idled EXTREMELY rough when I started it up; rough to the point that the entire vehicle was shaking. The Check Engine Light was also flashing, and the car accelerated weakly.

    The car is now in the shop, but they may not be able to get to it until Monday (Saturday afternoon when I dropped off). Off the top of his head the mechanic said it could be a wiring issue or the fuel injector.

    Can you speak to whether either of these diagnoses are likely and let me know if there are other more serious issues that I should prepare for?

    Thank you!


  184. Hi Robb,

    I would suspect an issue with the ACVS (Active Cam Shaft Timing System).

    It can be anything form a failed solenoid, incorrect oil filter, low oil level and more.

    We would start with oil level, and solenoid checks.

    We do a few solenoids here, I have witnessed the Jarring occurrence of an accident cause issues with the solenoids.


  185. Hey Justin.

    What an awesome site! I have a 2005 Subaru Outback and the CEL came on about 3-4 weeks ago. It is not flashing and it doesn’t stay on. It appears to come on when my gas gets to around a half tank or lower. After I fill up it will turn off after about three times of driving. I have smelled a burnt rubber smell a few times after driving it.

    Any ideas would be greatly appreciated.

    Thank you.

  186. hi my name is annie
    i have a 2006 sub.. legacy car shape.. lol its gt and has a sport automatic drive feature. 74 k
    just bought it used..
    got a the CEL steady and cruise blinking..

    turned the car on a few days ago .. it sputtered a bit and cel blinked a few times.. lack of power in exceloration.. for a few moments..
    then everything has seemed fine since..
    checked the gas cap ect..
    the error code was 303 misfire on cylinder 3..

    just thought id see what ur comments where and what u think of running gas with and with out ethanol in the engine..

    i was told to try ethanol free gas and also a stabilizer and ethanol remover to try and clear it out of any water or ethanol and debris..
    then was told if thats not it to check spark plugs and then some coil gas distribution thing if things do not clear up..

    just curious what your thoughts are..
    thanks a ton.. for all your info and comments..

    a quick question for the newbies..
    what is a drive cycle and how long dose that take..

    id like to get my cruise back on.. and this light to go off.. lol

    thank you so much
    annie d

  187. Hey Justin,

    Thank you for this great forum. I have read throught the posts and found that I seem to have a unique problem.

    I have a 12/01 Forester with a CEL that seems to have a mind of its own. Sometimes will not come on at all during the first drive but if the car is turned off and then started again while it is still warm it will most certainly come on again. Car still runs great.

    The real problem though is this. When I hook up an OBD-II reader to the port I cannot get a link. I have taken it to the mechanics and they have tried a few different testers and checked some fuses all to no avail.

    Is there a fuse that supplies power to the OBD-II port or is there any other reason why the OBD-II port would not be functioning?

  188. Justin
    I have a 2000 legacy with intermittent no start and code P0340 (camshaft position, right?). I replaced the camshaft position sensor with an aftermarket, then with an OEM from the dealer since the start problem and code came back. After replacing with the oem a few days ago, the no start and p0340 is back. It did start after letting it sit for an hour or so. Any advise would be greatly appreciated.

  189. Hi Paul,

    I really havent ever tried anything other than the Subaru Select Monitor. But I will Tell you that typically if you have no communication with the cars computer that the computer itself it was is at fault.

    I would encourage you to look FOr a shop with A factory scan tool AKA the Subaru Select monitor and take it from there.


  190. Hello Jeff,

    Having a Po340 isnt an automatic that the sensor has failed. We would test the circuit, but you probably cant do that, so its difficult to guide you here.

    The possibilities are enormous, If you want to try a couple of things your self, start with inspecting the cam sprocket , followed by the crank sensor.


  191. Justin,

    Awesome job with the site . . . just bought an 08 Subaru Outback XT w/ 52K yesterday – driving home today and CEL comes on with Traction Control light as well. We’re taking it in tomorrow to our mechanic to hook it up to the OBD – and then maybe onto a different Subaru dealership if that doesn’t pan out. Any ideas?


  192. Hi Justin – 2008 Impreza 2.5 w/ 24,000 miles. Check engine, Stability Control lights on. AT and ABS lights on most times – but reset after engine off. Cruise light blinking. Poor gas mileage (apx 15% worse than usual). Warranty repairs (less than 36 mo and 30k miles) by dealer two times – in the shop now with them now for third repair.
    Problem occurred with vehicle slow down to ~ 50 mph and then accelerate. Auto Trans shift/lurch and light show. Called dealer (200 miles away). They instructed me to go to auto parts store and get codes. Read codes (5 total) to dealer. O2 Sensor and Transmission solonoid were the two major (sorry I don’t have the code numbers..). Brought vehicle to dealer. Returned to me twice. The same problem returns. One time 250 miles later. Second time within 10 miles of leaving shop. They have said that the problem does not come in hard (when they reset the codes) – it’s an intermittent problem so they don’t want to just change parts. Am I out of line to expect them to return the car to me with all the safety features working? I really worry about driving without ABS and stability control. I hope that this problem is fixed this time. I worry that the dealer is kicking the can down the road until the warranty expires. can you suggest any strategy for getting cooperation from my dealership?
    Thanks much.

  193. Justin,
    Looks like a lot of great helpful hints to a wide variety of topics and I’m hoping that you’ll be able to dish out a bit more expert advise! As with many, this pertains to an illuminated MIL related to emission problems. After an air, fuel, and oil filter change, throttle, pcv and top engine cleaning, and plug replacement, I replaced my dual cat system and rear 02 sensor (from OBD code p1151), cleared the code with a scan tool and unplugged the battery overnite. Soon after or near the end of one drive cycle, the same code appears. After checking and clearing this 4 times, my freeze frame data seems erroneous as nothing matches up. My readiness test, however, continues to indicate incompletes on cats, evap system and o2 sensors. Should I continue clearing the DTC (if so when?) and will this affect the supposed drive cycles/trips that need to be completed to “reteach” the ECU? (what i understand is that there is “hard” memory storage that does not clear with a battery disconnect or scan tool clearing and that there is a “secret” driving approach to feed the ECU needed parameters to override this old storage of memory. One weird thing happened as I was driving after clearing the code for close to a half hour: the MIL flashed 4 to 5 times, which scared me pretty good, but could that have been a reset indicator? The MIL came on the next time i started it.) I have yet to check voltages or switching phases on the O2s’ and i cannot find an air or vacuum leak. I have not phsically checked the EGR system. Any thoughts on the readiness stats or otherwise? Either way, a Happy Thanksgiving to you and yours!
    -Tim in Trouble

  194. This site is a tremendous resource. Thank you.

    I thought I would add my recent CEL experience here. I own a 2004 Subaru Outback with 80K miles and have had the battery run dead a couple times. I decided to change it yesterday while I had a little time off for the holidays. I swapped out the battery and went to start the car up and found it was really rough (shaking badly) on the idle and my CEL was blinking. I also smelled exhaust/fule and saw visible exhaust from the rear. This was yesterday afternoon. I tried to call my local (Denver – Suba Performance) Subaru shop but they were closed for the holidays. This morning I took it to Autozone around the corner to run the CEL reports. It came up with 8 or so codes running from cylinder misfires to emissions problems to timing belt issues. The car was running great before I swapped the battery and I had recently had a full check-up. The timing was just too suspicious with the battery change, so I had them clear the computer. I started the car up again and bam, it runs great again. I will give my shop a call when they are open again and run them through the problems I had, but in the mean time the car is running great with no CEL blinking. Thanks again for the great site! Tons of valuable information here.

  195. Thanks for the info, Justin, you have helped me to understand my options with regards to the cel on my 2001 forester. I’ve let my subie owning brother in seattle know about your services.

  196. Pedro,

    Unfortunately it sounds like you have a problem child, we have our share of them as well.

    The best way I can explain it is that your car has several computers that are networked together like a small office network of personal computers. Sometimes a glitch in a data stream from one sensor or data that is shared form one module to another will cause some symptoms including a check engine light, and any other affected system to trigger the warning light for that system as well.

    As much as I hate to say this, it may take the Dealer a while to get to the bottom of it due to how the service department is set up in terms of being payed by Subaru for warranty repairs, until they can find a defective part there is no pay in many circumstances and the tech that is looking at your car, while he or she will want to fix your Subaru also has a family to feed and will only be able in many cases to spend a minimal amount of time on it.

    If after 20 minutes of test drives and another 30 minuts of scanning and wiggling this and that, if there is no other cars they have seem with like symptoms to draw from they will stamp it Unable To Reproduce Customers Symptoms At This Time. It doesn’t mean they dont think you have a valid issue, and it really doesn’t mean they dont want to help but they need you to take the next step by talking to Subaru Corporate. Pressure from above the Dealer should help resolve the issue.

    That is a real world senario, I dont know if thats the exact case in the matter of Your Subaru but its the normal progression at most Dealerships.

    Interestingly enough I suspect its a sticking Transmission torque convertor cut solenoid, which can be tricky to diagnose and would cause other systems to be affected.

    Hope that helps


  197. Tim,

    I missed your post a while back.

    You have quite a situation as the readiness monitors wont reset until a particular drive cycle is met, and the event for each monitor is different, at the same time, they may and most likely will not reset while you have a trouble code. I wouldn’t have replaced the Catalyst and 02 with out performing a function test on the catalyst and you would have also had a P0420 set as well.

    A flashing check engine light indicates a misfire. And should be your priority.

    Most likely my post is too late to be of any good to you, we had someone fill the server with spam in November and I did mis a lot of questions.


  198. Hey Mark,

    If your 2004 is EGR Equipped with 4 or more 02 sensors, you have one of the early PZEV vehicles, and yes a battery installation can cause issues.

    Here is usually why though

    It can be a sign that the new battery had a low surface charge at time of install and right after it was drained some more by the starter, there was low system voltage, the multiple 02 sensor vehicles in particular need proper voltage and amperage as the heater circuits for the 02 sensors hog a lot of amperage from the electrical system.

    If the system voltage was low all sorts of codes can and will pop up and the car will not run right, some of these require the system to be reset as the computer is in a fail safe or limp mode to get you to stop driving it.

    By the time the codes were cleared the battery was probably charged just enough that the system was ok, but I would encourage you to have the battery LOAD tested, as while it may still start the car, it may not in extreme conditions and worst be causing unknown negative issues to your vehicle by being in a state of discharge or have a weak cell. This over time can cause a lot of expensive problems.

    Thats my advice


  199. First, I want to thank you for this website. I’ve read through the majority of the questions and your answers and it has been very helpful.

    I have a 2002 Outback Sport with 180K miles. I recently returned to Texas from Denver. On the way back, my CEL came on. We immediately pulled over and my BF inspected the engine (he works on my car) and I checked the gas cap. Nothing seemed out of the ordinary (no smells, runs smoothly, etc.).

    Later that week, a local mechanic told me that I needed a new catalytic convertor based on my P0420 code. He also said there was another code concerning system being too lean (I think P0300 series, but I’m not sure), but that I should address the P0420 code first. My car runs smoothly and there are no rotten-egg smells. I suspect that my O2 sensor needs replacing, but I’m not sure since that code didn’t come up in the report.

    I know that I will have to fix the problem sooner or later, but in the meantime, my BF disconnected the battery (to clear the code) and I have added fuel treatment cleaner to my fuel. I’ve driven my car and I haven’t seen the light. Here’s my questions.

    1. What is your opinion regarding ethanol gas? I do a lot of highway driving, but I normally use non-ethanol gas. On this particular trip, I used a variety of gas. I know you mentioned earlier that it shouldn’t make a difference, but is it possible that the ethanol clogged my system, especially since I normally don’t use that type of gas?

    2. Are there any particular symptoms that I should look for if my catalytic convertor needs to be replaced? I’ve heard that rotten-egg smell or a poorly running engine might be something to look for, but I’ve noticed that you haven’t said anything about that, other than knowing the codes. It seems like majority of us on this site are running into the same problem. Un-qualified mechanics are looking at our Subies and telling us to replace/repair an item because of the code. Is there something else we can look for that might help us determine if they’re correct?? The P0420 code could be anything, right?

    3. Other than replacing the CC, is there any other way to clean/clear the system?? I understand that maintaining a vehicle costs money, but I’m not in a financial position right now to spend thousands of dollars to replace my CC, especially when it appears that may not even fix my problem. I was hoping that there is a cheaper fix that you might suggest.

    4. How many drive cycles does it take for the car to return to monitoring emissions?? I’ve driven it for a few days on the highway and the light hasn’t come back on, but I’m not sure if my system is being monitored right now since its’ been cleared.

    Thanks again for your help!

  200. Hi Justin
    I have a 2006 impreza sport outback. 120000mi
    yesterday it shook a little bit on low rpms . and it did again today. the “Service engine soon” light turned on. and the “cruise” control (green) light is blinking.
    what do you think could be wrong? i was planning to drive 130 miles tomorrow :S

  201. Hi Kat,

    There really aren’t black and white answers to your questions I am afraid. Ill do what I can to try and answer your questions though.

    A drive cycle is made up of drive events, an example of an event is drive the vehicle 45 mph with less than 5% throttle increase form start of cycle for 10 minutes without braking.

    By now its possible that 8 out of 10 are reset, the Catalyst and Evaporative emissions being the last to turn to ready status.

    Once the Catalyst monitor is on the Computer will have to see the fault for a few consecutive ties prior to illuminating the check engine light and setting the code.

    You can try having an induction service done, run premium fuel for a bit, and drive the vehicle at a higher rpm at lower speeds to create some exhaust temperature to help burn out carbon and contaminants that may be affecting the ability of the Catalyst to reach temperature.

    I will also share the unpopular truth Catalysts are about to become more expensive, if you watch Palladium on the precious metals chart it has continued a strong run and directly influences the cost of the catalyst. This is in part because there are more catalytic convertors in production as a result of all of the diesel engine snow having them including equipment and as a result of alternative energy such as solar.

    I guess that what I am saying is if you try to do some things to buy you some time and it doesn’t work out I would encourage you to budget for the Catalyst as in this case you could cost your self more money the longer you wait.

    The rotten egg smell doesn’t mean the Catalyst has failed and instead can indicate a fuel trim issue. Typically improper O2 sensor switching under load. Fuel trim switches from lean to rich in sweeps or cycles as the constant switch from lean to rich helps regulate Catalyst temperature and help improve Nox emissions as well. Sometimes when a car is loaded going up a grade the fuel trim is affected and the temperature of the catalyst suffers as a result such as not getting hot enough. One of the best ways to fight this is with Premium fuel which can affect combustion temperatures.

    As far as Ethanol, and Oxygenated fuels the issue usually derives from infrequent use. It is possible to have short term symptoms that go away with a different fuel but this can also point to larger problems within the fuel trim system or its ability to adapt to new O2 sensor data..

    I really wish that all cars would just display some basic code information rather than just the check engine light coming on, but its really complicated to way its not that way. It may be a good idea while you are in the try this and see how it goes mode to buy an inexpensive code scanner so that you can periodically check codes to make sure there are no new codes behind the PO420

    I hope this helps


  202. Richard,

    Your Check engine light coming on is a malfunction indicator light its yellow and means procede with caution, in 2005 Subaru disabled the cruise control system and commanded the cruise control light to flash whenever the check engine light comes on and a code is set in memory.

    As far as what is wrong there are Hundreds of Codes, thousands of possibilities, some serious and inexpensive, some very expensive and not all that serious.

    If you dont have a good shop that you can call and stop by for a quick scan to make sure its ready for a short trip , I suggest you ask your self why and what would you do tomorrow if you your self felt very sick?

    Owning a car and not having a good relationship with a good independent shop that can advise you as things can and will come up is just a terrible idea. At a minimum you should be able to stop by a parts store and have the code scanned if you dont have the above relation ship, you can post the code here and I will try and advise you about your next steps.


  203. Thanks for your quick and thorough response! I’ll probably look into the induction service and premium fuel for now, and pray that my car holds out til my inspection this April. If it’s my CC, I’ll probably get a newer car rather than spend the money on this one, especially since I already have 180K miles on it. This could just be the beginning of bigger issues down the road, and it doesn’t make financial sense to continue spending money on it. Plus, I’m looking forward to owning my next Subie anyway! 🙂

  204. Hi Justin and Team,
    I have found your articles extremely helpful however, I have a question that I am hoping you can help me with?

    I have a 1999 Subaru Impreza GX and for several months now my check engine light has been coming on at all different random times. The scarey thing is though, is that I loose power when the light comes on, I can put my foot flat to the floor and go literally nowhere. It is almost like the car is going to cut out, or there is a problem between fuel amd air. I get burts of power and then all of a sudden the light will go off again and the power of the car returns to normal.
    I have noticed that it happens more so when the car is really cold (so first thing in the morning), or really hot, like its been sitting in the sun all day and i start the engine, however, it can also happen just when stopped at traffic lights or going up a hill.
    I have taken it to 2 different mechanics and they have both run the code scanner on it and both times nothing has com up. They are puzzled and dont seem to know what the problem is.
    The car has an after market exhaust which I did not fit, but does not have any engine modifications that I know of.
    I am wanting to sell the car now as I have had it for 5 years now and it has never missed a service, but I do not want to sell it if it is unsafe or I cannot fix the problem?? Help me??

    Kind Regards
    Kate 🙂

  205. I have a 99 subaru outback legacy with about 180,000 miles.

    When the CEL came on last summer, the code said that I needed the air intake valve replaced. I have had that done.
    The light is coninuing to come on about once every two weeks and my car seems to and sort of sputters as it shifts into a higher gear. It sounds as if it isn’t runnning on all cylinders. The next time I drove my car it was totally normal and the light was off. My mechanic is not sure what could be wrong. Any suggestions. Thank you very much!

  206. Hi Kate,

    Since it happens mostly cold having someone scan for codes when its warm may not help much.

    It really needs to be looked at when its cold, thats the best advice I can give you, if the symptoms are reproducible its very fixable, but if its not easy to reproduce it can be difficult to get to the bottom of.

    I am afraid with out codes & sensor data there just isn’t much I can tell you.


  207. DeeDee,

    Without specific codes, some sort of sensor data there isn’t much I can tell you.

    There are hundreds of codes, and several items that can be wrong causing each code, than add the symptoms.

    The only air intake valve is the ISC(Idle Speed Control) and wouldn’t (as you realize now) cause the symptoms you are having. Instead the usual symptoms include an intermittent stall at idle.


  208. Hi Justin,

    We’ve got a 2001 Legacy 250T station wagon, the engine light is on solid as of today. My wife experienced loss of power and eratic gear changing (it’s automatic). I’ve just checked the code by pluging the 2 blacks togther and it flashed 10 longs and seven shorts… Any ideas what it may be?

    Many thanks, Matt

  209. Thank you for the advice Justin.
    I had an engine missfire. my mechanic changed spk plugs, ignition wires, and cleaned the injectors.
    he says I need to replace oil seals, valve cover gaskets and front hub bearing.
    any idea what price range are we talking about for that job?
    thanks again for the tips!

  210. I have a 1993 subaru legacy four door coupe 4 cilinder and the check engine light comes on. I would like to get one of those diagonostic things to plug under my dashboard so i want have to take it to a dealership. got any segestions

  211. Our 2003 Forester’s CEL went on yesterday and the idle got rough at the same time.
    The car passed the WA state emissions test just the day before and I can’t help but wonder if the emissions test is somehow related. Time to get it checked, though, right?

  212. Hello Phil,

    Because you have symptoms in correlation with the light coming on, you do what to have it looked at. The Emissions test has nothing to do with it, its “after” the test not “because” of the test


  213. This blog has been very informational. I have a 1997 legacy. The problem with my car does not pertain to the Check engine light. When I start my car, the battery and brake light comes on. It idles at a rpm of 1000 and if the battery was fully charge, in about 10 minutes it will drop down. There is something that seems to be draining my car battery, because before my car shuts down, the radio will turn off and the abs light would come on. Whenever I would put a newly charged battery in, it would work fine until it gets drained up again. I only way I get around with my car now is to plug both the positive and negative to the battery when I park my car. If I don’t then there is a chance of my car dying on me. On a side note, if I leave the positive side attached and take off the negative, my battery is still being drain. If you have any remedy to this I would really appreciate it.


    1. Hello Donny,

      You have a failed alternator by the sounds of it, very common on that era Subaru, there was actually a recall on that alternator as well for some models (typically the 1998 Subaru Legacy and Legacy Outback) . As Such the part is available very inexpensively form the Subaru Dealership and is the only part I would recommend for Your Subaru, nothing after market. The battery starts the car, and from there the alternator must power everything on the car plus charge the battery back up form the surface charge draw after the starter engages and drains it a bit.. If the alternator is weak and cant keep up with the electrical draw the car will have a hard time running and yes one by one the electrical accessories will quit as there just isn’t enough amperage to maintain everything.

      Hope this helps and good Luck


  214. Hi Justin,
    I have a 2002 Forester. My CEL turned on and off several times (in approximately 1-week intervals). When I had it read, it was said to be the catalytic converter. I ordered a new catalytic converter online and was going to replace it myself. The weird thing is, since I ordered and received the parts, the CEL has not come back. It’s probably been a month or more now since the CEL last came on. Is that normal? Should I go ahead and replace the CC even though the CEL isn’t on?

  215. Justin,
    I was reading up on a recall that Subaru had on the alternator, Recall 00I002000. Can I still take my car in for the recall?

    1. Hello Donny,

      You have to call a Subaru Dealership with your Vehicles VIN # than have them run the VIN # for any and all open recalls. I do think the Alternator recall is closed however.


  216. I have a long-standing relationship and friendship with an excellent Subaru mechanic in Madison, WI. This is my 12th Subaru – my 99 Brighton just had a transmission failure with 230,000 and probably will go to Subaru heaven.
    Took my “new” 2001 Outback MT in yesterday to get professional take on the P0420 code that it shows. Proposed solutions: leave it alone as it doesn’t affect driveability (we don’t have inspections) or cough up $1,800 for a new cat. Yikes! I do have a 3 mo/3000 mi 50/50 warranty that could help cover the cost, but it would still be expensive and inconvenient (work has to be done by the used car dealer’s shop – no relationship and little trust established. Plan to drive the car some weeks to see if the CEL comes back on. My mechanic cleared the code and added a fuel system cleaner. Almost all of my driving is at 65 on the four lane, so have a little hope that the cat might get cleaned out a little with this treatment. Any other insight or advice? Could get a direct fit Eastern Catalytic part for around $250 from RockAuto…they have a 5 year/50K warranty on the part. Is there any more testing of the fuel trim or O2 sensors that should be done before replacing the cat?

    Love and appreciate your very informative and expert advice to the many loyal Subaru owners.

  217. Hi Justin,
    I have an intermittent problem with my 01 VDC. When driving, I will feel the car give a little hitch (as if something engaged, like a brake or a gear shit). When this happens, the “VDC off” light comes on, then turns off and the car runs back to normal. The CEL light comes on. It is an intermittent problem, and seems to happen only in the winter time. Currently the CEL code is P1146.

    I’ve taken my car to a local independent Subaru mechanic three times for this issue. They replaced the Throttle Position sensor (twice) and the Manifold Air Pressure sensor, and after $700 of repairs the problem is still there. Do you have any ideas?

    1. Hello Erik,

      I really have no idea from here whats wrong, I would have to evaluate it at the shop to be exact, but I can share with you its very common on the H6 models to need a electrical Harness due to incorrect TPS values and is often mistaken for a faulty TPS. If you dig around the internet long enough you may even find a old TSB about it

      Causing all of the same symptoms you are experiencing.

      Hope that helps.


  218. Hi, a quick comment, i have a 2000 Subau with approx 175k on the clock. Recently the CEL came on, a quick scan showed knock sensor error. Cleared the code and started the car and the CEL came on instantly. Not having time to troubleshoot the problem, had the wife take it to a authorized Subaru repair center a hundred miles away. They replaced the knock sensor and the CEL came back on. They tried another Knock sensor with the same problem. They gave us a estimate of over $1000 to repair, and sent her home with a new Knock sensor and CEL on. I ended up troubleshooting it myself and discovered the wires leading from the connector on the sensor were shorted. Looks like the manufacturer of the sensor used heat shrink over the wires and must have overheated the wires causing the shielded outer wire to melt into the center wire. Thus causing the sensor to be shorted., as only one wire is needed, as the sensor itself is grounded!. Called the Subaru dealer and had them check the other sensors they had that fit this car and all were shorted like mine!. Anyway after a bit of surgery to seperate the wires everything works fine now!. And when the Knock sensor fails the engine sounds and runs bad!

    1. Hi Paul,

      You did in fact Stumble onto something that we are very well aware of here, it also points to the Subaru Dealer you took it to may not be buying all there parts from Subaru as there was a O.e parts supplier to most of the independent shops that do sell to some Dealers as well that had a huge batch of Defective part Number 22060AA071 Knock sensors. I am surprised they are still out there as we were aware f it a year ago.


  219. Have 93 loyale start up and go about 8 miles and stop at red light. Engine kicks down to 600 rpm and jumps to 1200 rpms. If you sit at light long enough the check engine light comes on. Light turns green and you go every thing works good till next light. This does not happen all the time. Any ideas? Thanks.

  220. Hi, I have a 96′ legacy wagon with a growing list of problems. Recently my check engine light came on and my car shakes at an idle and when accelerating feels kind of jumpy, like the engine isn’t getting fuel. Today the check engine light flashed at me and I figured this was a bad sign. The car isn’t worth an expensive repair, but if there is some cheap options I could fix myself I would be willing to try. Any help is greatly appreciated.


    1. Hi Eli,

      There are many possibilities, things you can try are plugs, plug wires. I have no idea if that will resolve your issue and it would better to have it diagnosed.


  221. I have a 2007 Legacy (not a GT) with 112,000 miles on it. We’ve had minimal problem with the car, but today, with no warning, it acted as if there battery was totally dead and would not start (no sound at all). I jumped the car with a battery pack to get it home and while driving the ABS and airbag lights came on and the cruise quit working. When I checked, I found the positive battery terminal was corroded and not making good contact. I cleaned the battery up and replaced the terminal with a new one. The car will now start, and seems to run fine, but the ABS and airbag lights are still on and the cruise will not work. I hooked my scanner up and it did not find any codes, nor did the CEL come on during any of this. Any thoughts?

  222. Just thought I’d run this by you, and see if you had any advice. I have a 2005 Outback that has a little over 80,000 miles. This is the third year in a row that I’ve had a CEL and flashing cruise control light come one, and throw the same codes: P0131 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1) and PO2– something– don’t have the number in front of me– indicating the mixture in the back sensor is too rich.

    I’ve already replaced the front 02 sensor twice at the dealership– last year and the year before. Last time they went ahead and upgraded the ECU as well. Since this is the third consecutive year that it has happened, I refuse to go back to them now because I can pretty much expect that this is going to be an ongoing thing with them, and they don’t show any interest in getting to the root of the problem.

    I’ve tried disconnecting the battery to clear the codes. It was good for a week or so, but now the CEL will fire intermittently. It usually will be fine for a couple of cycles, and then pop up when I drive across town. Just for grins I’ve had the front O2 sensor tested at a local Midas shop (they didn’t charge me for their diagnoses thank goodness), and it seems to work just fine.

    In each instance where the CEL problem has occurred, it seems to have done so right after the first good freeze of the year (I live in Colorado). I really don’t know if that’s relevant or just coincidence.

    Do you have any idea as to what could be going on here, or what I should do next?

    Thanks for any advice you can provide.

    1. Hello Dave,

      We have replaced a few Computers for that exact set of circumstances, it sounds like maybe the actual sensor was never tested correctly or when the sensor failed there was some “Voltage back feed” into the ECM

      The data needs to be graphed on the Subaru Select monitor III then check the resistance values of the sensor to figure out Exactly what is wrong. You need to find as close to us as you can in your part of town.


      1. I had it checked by the service department at a (much better) local dealership after the light returned and was solid for a couple of weeks. It turns out that now I’ve got a blown head gasket, and it was a slow leak that had most likely been the culprit of fouling up the previous O2 sensors.

        So I’m having the gasket replaced, the transmission fluid flushed, a new timing belt put in, and the O2 sensor replaced. Luckily most of that’s covered by the SAS warranty. Hopefully, that will resolve the problem from this point forward. Thanks for your advice.

  223. Justin,

    I have a 2004 Forester and the CEL is on and the cruise light is flashing plus it sounds horrible. This happened yesterday. I have had to replace the turbo 3 times. Does this sound like I have a fourth turbo in my future?

    1. Hello Alisa,

      Its hard to say with out knowing the code in correlation to the light.

      If it is s turbo I would make sure that the screen in the oil supply line is taken care of its listed by Subaru as a union screw.

      If you are not using synthetic blend oil and changing every 3k I would start.


  224. I just recently purchased (October 2010) an ’05 Forester XS that had been in a driver side frontend collision. The vehicle was recondition and I had the local Subaru dealership do an inspection prior to purchase to ensure the vehicle was sound. Well I’ve since put maybe 4k miles on the vehicle (odometer is now at 51,274) and I’m having issues with the CEL coming on.

    It started about two weeks ago when I was driving home and the cruise control disengaged and the CEL light came on. I took the vehicle to midas and had them scan for a code. The codes that appeared were P0031 (O2 sensor) and P2097 (Post cat fuel system too rich). They pulled the front sensor and it tested just fine so they suggested I talk to the Subaru dealer and see if they had any ideas. Called the Subaru dealer the following day and explained to them what Midas had indicated was the problem and the Service Manager informed me it was likely the Catalytic Converter and not an O2 sensor. I dropped off the vehicle and they charged me to run a second scan and reset the computer. Subaru wanted me to drive for another week or two to see if the CEL like came back on. Needless to say I didn’t even make it the full 10 miles home before the light came back on.

    The following day I took the Forester back to the dealership and they replaced the catalytic converter (under warranty) and sent me home. Again within 30 miles of driving the CEL came back on. I took the vehicle back to the dealer a third time and they said the thermostat was sticking in the open position so they replaced it (also under warranty) and wanted to keep the vehicle overnight to test drive it a few more times to ensure the CEL would not come back on. WELL IT DID! Over the course of the next two days they pulled good O2 sensors (both AFR and EGR) from new vehicles on the lot and neither of the new sensors stopped the CEL from coming back on. Now they are telling me the next logical step is to replace the wire harnessing but they are not entirely sure if that will fix the problem. They want me to spend $90/hr (for about six hours) for one of their mechanics to chase all the wires around and see if they can determine why the EGR sensor is firing a code. Then to replace the wiring harness would be anywhere between 1-4k depending on which harness (or both) needs to be replaced and the labor costs.

    I am super frustrated right now and would rather not spend a couple grand on this issue so I’d appreciate any insight you may have. In addition to the CEL, the day I picked up my Forester from the dealer the windshield wiper fluid dispensor stopped pumping fliud. In fact it doesn’t even sound like it is trying to pump fluid. When I called the dealership and told them it was working fine prior to them working on the car they suggested that I just chase tubes and make sure everything is attached correctly because they were not going to take responsibilty for the issue. If I could reach through the phone and ring a few necks I would have! I’m not a mechanic!

    1. Hi Nicole,

      I understand the frustration you have right now but since I am completely un biased at this point you wont like all I have to say. The single biggest issue you have is that you bought a previously wrecked and than repaired vehicle, there is no way for anyone doing any type of pre purchase inspection to know if wire harnesses that cant be seen were at all compromised in the accident. I am very surprised that the Dealer made any repairs under warranty if it in fact has a “branded title” and most likely Subaru will not reimburse them for any of it. Sometimes cars are hard to accurately diagnose, but it is your car at the end of the day. We here, always do the best we can and sometimes have a problem child as well, its not that any one is stupid, not trying hard enough, or trying to rip you off, its instead a complicated issue that needs more time and money spent than anyone wants to obligate, your money and their time. You can try calling SOA but since the car is way out side the 3 year 36k warranty it may fall on deaf ears. If you have lost confidence in the Dealer try another. But I would Guess that the one you are at now will be more sympathetic and interested in getting to the bottom of it


  225. Dear Justin, I am also driving a 2008 Subaru Legacy 2.0L. I have 40,000KM (25,854Miles) on the car.

    At 25,000KM i started experiencing a shudder in both Idle and in drive while brakes applied at a stop. I still am experiencing this and have taken it to the Dealership here in Beirut, Lebanon. They have run it through the computer and told me nothing is showing up as wrong but i might need to replace the injectors. This car hasn’t hit 30,000 Miles yet and i purchased it brand new???

    Today the CEL is on and Cruise is flashing..

    I know several people who no longer take their cars to the Dealership here as they claim their problems were never solved and their local mechanic is more knowledgeable.

    I am lost and don’t know what to do.

    Can you list just a few things that might cause these problems as i wanna compare it to what the dealership might tell me this time.

    Best Regards,


    1. Anthony,

      Its not that I don’t want to help but you have to understand there are just to many possibilities to just list. There are thousands of possibilities. With out at least a code number there is no starting point.


  226. Can i reset my CEL by disconnecting the battery cables overnight safely?
    I have heard that the trip odometer and radio channel sets will need reset , but other than that ..any thing else to be aware of….

  227. Hi
    I just bought a 99 Legacy GT auto.
    The VDC light comes on aswell as the CEL.

    These lights only come on intermittently how ever yesterday when i was driving it it felt like it lacked power and a couple of shudders the lights flickered then finally the lights turned off for good and it was fine again.

    I am going in on monday to get it diagnosed but would just like to hear it from you. What are your thoughts?


    1. Hi Lyndon,

      With out codes their is nothing I can advise you on.

      I have said this a hundred times the light is an alert to check codes, once the codes are known the codes are checked, a Technician or vehicle owner can go from there. Without knowing the codes their is nothing I can evenly remotely suggest to you. Its kind of like telling me your real sick, the next step is to test.

      Sorry but thats the best I can offer you.


  228. Hi justin, What a generous man you are to spend so much time answering questions.

    I just bought a 98 Outback wagon spec.ed. with 185 thou kilometres on it.
    I was shocked to read elsewhere about the overheating problems through faulty head gaskets and am hoping the problem was contained in Nrth America – am I being gulible here?
    Anyway, my CEL came on after 300 k’s but goes off on it’s own.
    After a cold/cool start about five or ten minutes in, the light illuninates and stays on for five or ten minutes then goes out untill the next cold/cool start. I’m thinking (hoping) that the diagnostics are measuring the engine temp. between the opening of the themostat and the starting of the thermo fans. The light seems to go out after the fans start. All levels are good and the engine does not run hot. The fuel cap is tight.
    This car was serviced by Subaru over it’s life regularly.
    Do you reckon I have a problem? It’s due for it’s 187500 service in a thousand ks and I will have the problem checked out then if the light continues to go out and stay out.
    Otherwise, what a brilliant little car.

    Thanks for this site, I’ve learned a lot reading it.

    1. Hi Andy ,

      It would be best to determine the cause of the Check Engine light and take it from there, typically the Blown head gaskets do not set a Check Engine light. The check Engine light is typically due to a sensor or Solenoid issue or some sort of a condition present that the Computer does not like based on programming such as a rich or lean fuel mixture.


      1. G’day Justin,
        Thanks for your reply. I took my Outback to the Subi shop and they found an oxygen sensor fault in the memory. They cleared it and the light has not come on since. I sort of suspected this as I had taken your advice you gave someone else and ran the car slowly at higher rev’s to get some heat into the cat. That seemed to help so I’m hoping I get a half decent run out of this great little car even with the hundred thousand plus miles already on the clock. I’m off on a thousand Kilometer trip next week with temperature forcasts of 100 degrees F. That’ll test the old girl!
        Brilliant site you have – you know your Subis!
        Cheers, good luck and good health to you.
        Regards, Andy.

  229. getting a p1440 code on 1998 impreza rs. having tough time finding info on troubleshooting this.

    thanks for any help, steve

    1. P1440 pertains to the Evap system not holding pressure. You can go to Alldata online and purchase the information pertaining to the diagnostic flow chart.

      I wouldn’t be able to offer much with out testing. Its hard to teach you things I have learned over the last 20 years in a few paragraphs.

      The Computer thinks there is no tank pressure, so either there isnt or the monitoring system is faulty either way there is some testing that needs to be done.

      You can start with looking for leaks in the system (visually) We would uses a smoke generation machine.

      Sorry I can offer more


  230. Justin,

    I’ve just changed the head gaskets on my 2001 Outback 2.5l Automatic. After putting things back together I now have a blinking CEL and 4 codes that won’t clear.

    P0500 Vehicle Speed Sensor Malfunction
    P1540 Vehicle Speed Sensor Malfunction 2
    P1590 Neutral position switch circuit high input
    P1591 Neutral position switch circuit low input

    If check and rechecked the connectors to make sure I have them all reconnected. I didn’t touch the connector to the VSS during the repair but since have checked and know that they are all firmly connected.

    Thoughts? There is an aftermarket remote start system installed and a toggle switch near the foot of the driver. I assume this is part of the remote start and I’m not sure it position this switch is supposed to be in but I’ve tried both up and down.

    Thanks for any help,

  231. Dear Justin,

    We have bought recently a Subaru Outback 97 model. some 2000 miles runs very nice, good on fuel 11 km on 1 liter, according to the day counter. Now a few times, when driving very slowly the engine started run roughly. Remedy: stop car put in P and restart problem is solved for maybe a week or so.

    The CEL is not working so not burning.

    Do you have an idea what the problem can be? and is it bad for the motor to drive on with this problem?

    1. Hi Joep,

      You really shouldn’t drive it until you resolve the run ability issue, you could be doing some damage.

      I dont have enough information at this time to be able to guide you much further, I would take it to a Subaru guy in your area, as it may be difficult for you yourself to get to the bottom of.


  232. Justin,

    Thanks for taking the time with all of us! My 16-year-old son drives a ’95 Legacy Outback wagon, 2.2. Last week, it just quit running in the middle of the road. (For a small wagon, it was very heavy when we had to push it uphill in the middle of Main Avenue!) Anyway, he checked the battery – it’s great; replaced the plugs and wires; replaced the ignition coil; replaced the fuel pump and strainer. $350 later in parts and NADA, ZIP, ZERO, ZILCH. It makes a strange noise – kind of like those old button-on-a-string spinner toys. It won’t turn over at all and doesn’t even sound normal. I absolutly have to get this thing back on the road by Monday morning.

    Any thoughts or suggestions?


    1. Hi Debbie,

      Sounds like a broken Timing belt I am Guessing from here though, be sure to have all of the timing components inspected and replaced as needed as part of this process if after a good diagnoses thats what is found to be wrong. This would include the 3 idlers, tensioner pulley and waterpump.


      1. Thanks for your imput. I was thinking timing belt, as well. It looks very worn. There has not been any characteristic water pump squeal at all. Sounds like it’s time to call my adult son home for the weekend!

  233. Hi Justin,

    Thanks for quick responce. I will visite a nearby Subaru mechanic. If he cannot solve the problem I will come back to you with all the information I have.

    Thanks again!


  234. Justin,
    I just purchased a 1995 Subaru Legacy L wagon from a friend. It was garaged, kept up well, etc – only has 87,000 miles.
    They had a battery connection device (I think they had it on there because the vehicle wasn’t used all that often) that they took off the day I bought it. As I was driving it back home, the check engine light came on, something that had not turned on before. The car has a new Optima battery, so I don’t think it is a battery issue.
    I’ve got to register the car and pass emissions ,and I’m wondering if the disconnecting and reconnecting of the battery might have had something to do with the check engine light. If so, how I can fix that?

    Thank you for your help,

    1. Hello Peter,

      There is no way to know why a check engine light is on with out first a code scan, and then some diagnoses as needed. The light would not have come on due to the battery being disconnected.

      The one light has many possible meanings, there is no way to guide you other than to say at a minimum you need a code scan and take things from there.

      Hope that helps


  235. Hi,
    I have a 2005 Saab 9-2X, sometimes called a Saabaru, lol. She has the Subaru boxer engine, body and safety features by Saab, and I’m not sure who did the bits in between, such as the emissions system. I bought her new at a Saab dealership and she has about 47K miles.

    Anyhoo, recently the Check Engine light has come on with the blinking Cruise Control light. As you can tell by the mileage, I don’t drive much and the weird part about the lights coming on is that it’s a very brief and infrequent occurrence.

    The first time it happened, I had filled the gas tank and was on my way to get the car washed. After the car was washed, the lights went off so I thought that perhaps it was a dust problem. (I live in West Texas — it’s VERY windy and dusty here.)

    It happened again several weeks later and it was the same deal. Very brief. A few days ago, it happened again after I filled the gas tank. I haven’t driven the car since then so I don’t know if the lights are coming on or not.

    It hasn’t happened with every fill-up but, then again, I don’t get gasoline at the same place every time. Since the lights don’t stay on persistently and it’s very brief, could this be a gasoline issue?

    I’ve had no problems whatsoever with the car’s performance and haven’t noticed any variation in gas mileage. Any tips or anything I can try?

    Unfortunately, I’ve moved to a different area since I bought the car and no longer live near the excellent Saab dealership. The closest Saab dealership is about 170 miles away, grrrr. Could I take her to a Subaru dealer for service? We do have one in my new city.

    Thank you for your help!
    Julie-Anne (and Sophie Rhys-Saabaru)

    1. Hi Julie-Anne,

      Actually the 9-2x is much more Subaru than Saab. It is a Impreza with a very small amount of trim changes, the safety systems are all Subaru ABS, SRS etc.

      You have an intermittent check engine light. The fact that the light comes on isn’t as meaningful as what code is set, without that information there is really not much I can offer. You need to have the Engine Control Module scanned for codes after the light comes on next and take things from here.

      Sorry that I cant offer more


  236. Thanks for all the great info. I see there are others having the same issues as I am:
    2005 Forester XS, 109,000 miles, has a cylinder 4 misfire. Car idles rough, but runs fine when accelerated.
    -changed ignition coil
    – NGK plugs
    – wires
    Didn’t fix problem so I took her in to a local mechanic who works on Subie’s. Compression test came back with low compression in cylinder 4. No sign of a head gasket issue and mechanic thought it could be a crack in the cylinder. After researching online it sounds to me an exhaust valve could be an issue. I used a tip and put my hand over the exhaust when running and there is some suction occurring. Is this truly a sign of a valve issue? I also read that a person with the same issue used a quart of marvel mystery oil that helped loosen an exhaust valve stuck open – Could this be a quick fix?
    What can I recommend to my mechanic to diagnose problem?

    Thanks so much,


    1. Joe,

      If your Guy cant figure out that a compression test is just step one in locating a mechanically related deficiency and a leakdown test is next to determine why, there just isnt much else to say.

      There is no fix other than a repair for a burnt valve


  237. 8 Outback head gaskets dohc, do i need to replace the head bolts, i will be getting all the parts fron you. Andy

  238. Hi, I have a 98 subaru imreza outback sport. The CEL recently came on showing 4 codes, claiming misifires in all four cylinders. However, the car is idiling smooth, running smooth and doesn’t seem to have any other problems. The last time a misfire code appeared it ended up being a knock sensor that was accompanied by extremely rough running engine. All of the spark plugs have been recently replaced. Is there some sort of sensor or problem that can confuse the car into reporting misfires when there aren’t infact any occuring?

    1. Hi Alex,

      There are lots of possibilities there isnt really much I can point you towards replacing based on the limited information you can provide me with. We make determinations based on data from sensors with out that its all just a guess.


  239. Hey Justin,
    As with many others my CEL suddenly came on. I have a 2001 Subaru Forester. I checked all fluids and everything sounds O.K. My neighbor hooked the car up to a hand held diagnostic tool. Three codes popped up P1540 (speed sensor), P1590 (neutral switch circuit high), and P1591 (neutral switch circuit low) do you have any suggestions for me to correct these myself? Thanks for your time and expertise!!!

    1. Hi Robert,

      If its a manual you can check the Neutral switch for an open. But realistically with out the ability to capture and interpret data its going to be hard to diagnose. We would look at Data from the sensors to determine if they are ok, I know no other way. Sorry I cant offer more.


  240. I replaced my front and rear oxygen sensors on a 2001 subaru legacy gt wagon, 2.5 liter engine. I’m having a problem with the wiring order of the rear. I accidently disconnected the 4 wire “pig tail” and now I don’t know which wire goes where. By “pig tail” I mean the unlabeled white, square, wire connector that has 4 square, female openings that you connect the 4 O2 sensor wires into.

    I used a bosch o2 sensor (install instructions are here, which include a color code reference chart it’s the first one under oxygen sensors).

    Do you know which wire goes to which pigtail connection?

  241. Hi Justin,
    I just ran across your website and hoped to find an answer to my question but had no luck. However, you do give great advice. I do have the codes for my 2000 Outback Subaru but I should first tell you some history of the beginning of my troubles with this vehicle. My ex worked at a mechanic shop, yet he only did inspections and changed tires, he just thought he was a mechanic. Anyhou, I bought my Subaru in Aug. of last year and the CEL was on then, so he brought his diagnostic tester to where the car was parked and the guy was selling was and we ran the codes, which was the knock sensor. So the guy lowered the price by $500 dollars on the spot. I really wanted this car. I need an AWD. I drove the car and I had no problems at all out of it. He did the oil changes for me at the shop he worked at two to be exact and I was planning to have the knock sensor replaced before I had to have it inspected which was this past March. I should have done it as soon as I bought it, but hind sight is 20/20. The second oil change I thought was fine. I got the car back and everything seemed fine. We had been having some relationship issues though. Anyway, one night, it was dark he said he was going to check the oil. I walked over there with him and he checked the coolant too and said it needed some coolant so he poured some coolant in it. He stayed a while longer and then left. Well, to make a long story short he moved out and we now both hate each other. To make another long story short. Before he even left but after the oil change I noticed a burning smell when I would start the car up. I asked him about it and he just said, “every car has it’s own smell.” I just didn’t buy that one. I just didn’t make any sense to me, it really was a burning smell. Well, I live in a place called Love Valley, NC the Cowboy Capitol, where the horses have the right away. We don’t have much here but we actually do have one mechanic. Now, after the ex had left I took my car up to the mechanic just to see if he’d look at it and him and my neighbor were there. They lifted my hood and low and behold they checked my oil and it was almost a qt. over filled, never mind that when they checked my water over flow compartment there was oil mixed in with the water and coolant! I was so shocked and didn’t know what to do. I mean at first I thought blown head gasket so my neighbor told me to drive it straight home and don’t drive it anywhere else until we figure out what to do. I live about 2 min from there. The mechanic knew nothing about Subaru’s. It’s not like I could confront my ex, he would have just denied it. So my car just sat there for about 2 months. Finally, my neighbor said why don’t I just drain all the water and oil and flush the radiator out and then we can see if it happens again. My neighbor was thinking that the ex put the oil in the overflow reservoir! I don’t know, but I do know that the oil has not returned to my water reservoir, it is still a bit murky but my neighbor told me it was. Also, he said there was no oil at all in or around the radiator. I called a local and highly recommended car shop here and explained what happened and he said he had never heard of oil being in the water overflow and that being a symptom of a blown head gasket. The fact is I still have to have my car inspected and my tags renewed so I took it to an Auto Zone (we don’t have a Subaru dealership here) here are the codes :

    1) PO325 OEM Domestic
    Knock sensor condition
    explanation:The powertrain control module monitors the Knock sensor signal for errors
    Probable Cause:

    a.)Knock sensor defective
    b.)Check connector and wiring to sensor
    c.)Engine mechanical condition-knock or rattle in engine
    d.)Low fuel pressure

    2) P1133 OEM Subaru
    Front Oxygen Sensor (AF) Heater Circuit High Input
    Probable Cause

    a.)Open or short circuit condition
    b.)Poor electrical connection
    c.)Failed oxygen sensor (AF)

    I was given a quote just to replace the knock sensor of a$200. Should I be expecting to have to replace all of these things. I do know I have some wires crossed somewhere because my low beams do not work, so that definitely needs to be addressed. I am wondering though if using the better gas would help me out in anyway? Any advice you have for me would be greatly appreciated. Do you think I could have a blown head gasket? Or do you think and “accident” happened? Thanks.

    1. Most likely for the P0325 you have a faulty Knock sensor.

      For the p1133, the problem could be the heater has shorted out in the O2 sensor, but if allowed to go on to long it usually damages the driver in the ECM.

      As far as the rest, Im just not sure what you are asking for? ” called a local and highly recommended car shop here and explained what happened and he said he had never heard of oil being in the water overflow and that being a symptom of a blown head gasket”

      Really, this is pretty basic stuff that any professional should know about kind of like a carpenter stating he didnt know you could use a hammer to drive in a nail.


  242. Dear Justin,

    We have a Subaru Outback 2.5 1997 autom. We are with the car in Argentina and a problem came up: fault code p0325 keeps coming back. When the engine is cold there is no problem, but after a lot of miles and heating up on one day the car hesitates when accelerating at a traffic light with a squeeking noise. At higher rpm and constant speed no hesitating occurs.

    Do you think a replacement of the knock sensor is mandatory? If so do you know what type of sensor we need, there are not many subarus sold in Argentina so it is very difficult to get subaru parts. Is the knock sensor also used for different brands of cars?

    Thanks in advance and best regards


  243. I have a 2005 Outback Legacy..CEL came on and cruise flasing. I just had a tune up last week with new wiring and spark plugs. Took it to Advanced Auto and got the code. P050 – Idler Air control systems revolution lower than expected. Can anyone tell me what needs to be replaced. I’ve gotten everything from 02 Sensors to a new Idler Motor. Help.


  244. Dear Justin:
    I have a 1998 Outback 2.5l/4cyl, 161k miles on engine with mufti-error codes on check engine light such as misfired Cyl#2, malfunctions and lost the radiator’s coolant.When I ran it on idle speed, sounded it didn’t run with all engine’s power.

    I paid total of $2500 to replace the head gaskets with the valve job, T/belt and h2o pump, replace the radiator with new hoses and thermal valve, new coil box and plugs.
    I got the car done and it ran stronger and smooth. But after a first few hundreds miles, the check engine is ON again, I brought it back to my mechanic and he found only one code p0400 for the error of EGR system.

    Can you please explain which cause this problem and how to fit it and which component(s) I have to replace prior to take my car back to repair again?

    Thank you

    1. Ben,

      There are many components to the EGR system, the valve, transducer, solenoid, pressure switching valve and the vacuum sensor, vacuum lines, wiring and the ECM.

      Some parts for the EGR system, some for the EGR monitoring system.

      There is just no way I could possibly know from here what is wrong? Could be as simple as a broken vacuum line or as complex as a defective ECM.


  245. Hi Justin,

    I’m traveling and stumbled upon your website in trying to research my problem. Whenever my car exceeds about 3000rpm, my check engine light pops on with a misfire. P0303 and P0304. I don’t know how pertinent this is, but the spark plugs and wires and the ignitions coil have just been replaced. Any ideas for a man on the road?

    Thank you!

  246. I need some help please I have a 1996 Subaru Legacy when I drive the car for a half hour or longer on hot days using air condition If I stop the motor and try to start it again I have to sit and wait for my car to cool down before it will start again. the engine light isnt on and its not showing hot either. Thanks

  247. Dear Justin, greetings,

    Mine is a Subaru 1996 Legacy wagon, Both my partner and I enjoy this vehicle even if it’s a little long in the tooth with 186,000 kilometres.

    I have a mate who swears by his Suby mechanic (we’ll call him Ben) but it takes weeks to see him. In the mean time I’m attempting to have a shot at it myself.

    The problem is intermitant, feels like it is starving for fuel or running on 3 or less cylinders, I have had some luck in recreating the fault. It is most prevalant after climbing a slight incline (say 10 degrees) for 200m (this is in the suburbs)at the end of the 200m the road levels out for 50m then a slight decent 5 degrees for another 50 and levels out. For the next couple of hundred m it plays up something awful. With occasional engine stall. I’ve just been informed that it pretty much hates all hills.

    I have changed fuel, oil and air filters, plugs, leads, battery and MAF sensor. The MAF as recommended by another Suby Dealership/Mech when it went in originaly to correct this problem, They also suggested that decarbonizing the valves would be of an advantage, the let some water in through a vac line trick, I have not done this.

    Changing the MAF showed improvement for a couple of weeks, but as in your posts it has taken this time for the sensors to kickin.

    I got in touch with Ben, he sugested checking the fuel tank for impurities i.e. water. I did this with trepadation (yeh yeh I know), as expected there was some slight discoloration on the pump bag filter and some grit at the bottom, I took some samples at the lowest point and found no water.

    This though did have a marked improvement, possibly the pumps electrical connection.

    All well for a couple of weeks, but it’s back and sometimes back fires with the above condition. Q. will the backfiring upset the MAF?

    Today it left my beloved stranded around the corner. I have tried pulling the codes, no luck, the black then green both produce a constant flashing “check engine”. But what I did try today is releasing the vacum in the fuel tank by leaving the the cap loose. This has proved most helpfull. After pushing thru the 3 cyinder thing a couple of times the Suby has not faultered over 50ks of differant terain on the black top.

    Fuel consuption is awfull.

    I’m leaning toward fuel tank.

    I guess Ben with all his toys will be able to sort it out, but in the mean time,

    You opion valued.

    One other thing, I have heard water gurgling in the cab behind the dashboard whilst cournering also intermittant.

    Regards Dan

    1. The gurgle is the clue to air in the cooling system, you may have a HG issue, but if its a 2.2l I would also suspect dropped valve guides, you can verify this by dropping down the y pipe and having a look in the exhaust ports, there is video on our site showing what to look for.


  248. In my 2004 Subaru Forester, the check engine light comes on for a while, then goes off. It’s done this about 7 times in the past 4 months. This is not happening soon after filling with gas, so it is not related to the gas cap. It usually comes on when I am going down a steep, slightly bumpy dirt road away from our house. It usually goes off again about 24 hours later or less, by just not coming on when I start the car. It seems like it might be a loose electrical connection of some sort. Any advice?

      1. Does the light ever come on and off like that simply because of a bad electrical connection, or is it always related to the emissions system. it seems like the light itself is malfunctioning. I need an oil change and will ask the garage to read for a code then too.

        1. Its not possible for the light to malfunction the ECM sets the light when there is an issue, and depending on what system is affected turn it off as soon as its had enough drive cycle events to satisfy it, its different for each and every system.


    1. Thankyou Justine for your time. Checked out the video, out of my scope as a sparky. May as well have a port and polish, change belts etc. whilst the guys are at it. You have put me in the ball park, looks like the previous owners were unawares of a regular maintainance program. Would love to send the head over to you guys but cost restrictive from Australia.


  249. i have a 95 legacy 2.2 turbo auto tranny.. i popped a compressor belt and had to drive it home like 2 miles the car would start and sputter and i had to keep the revs up or it would die it and when i would put it in drive the revs would drop even lower and i would have my foot in it all the way and it would barley go… checked the codes when i got home it was p0301 and p0304 so i replaced the plugs and wires and now no more missfire but it still runs like crap.. starts up sputters and dies.. wont stay at an idle just dies unless i keep giving it revs… what do you think it could be… the only thing i think at this point is coil pack or the o2 sensor.. or somekind of sensor pleaseee help!!!!!!

    1. You need to first isolate which cylinder is acting up then figure out why, its difficult to teach you this in a few paragraphs.

      With drive ability issues there just isn’t much I can offer over the net or over the phone. I need factual information about the conditions of systems to know what is wrong, with out that its a blindfolded dart toss at the bulls-eye. You can try disconnecting the mass air flow and if it changes start by mapping its data to see if its out of range. Sorry I can t offer more.


  250. Hi I have a 94 Subaru Legacy and have just replaced the radiator, since replacing the radiator check engine light has been on and fans constantly working. Any idea what I should check first? Thanks

    1. Sounds like the Coolant temp sensor failed, very common after a cooling system service as the instant the sensor is no longer surrounded in coolant it can fail.


  251. Hi Justin, I am a long way from you but I have a Subaru problem. My CEL came on today but it is stable.I own a 2005 Subaru Impreza, Engine Type: EJ152DP8AE. I was first faced with the problem of white smoke from the exhaust on startup but only after the car had beed parked at a slanted angle with the right side dipped. Once the car is level in any direction nose up or nose down the car will not smoke. I thought of changing the valve seals, but I am in doubt now. I read on most of the threads and I am wondering if this may be the cause, affecting some component causing the CEL to come on? Car runs smooth and great.
    Need some help.

    1. You need to start with the code number, I am a broken record and I just cant stress this enough the check engine light is an alert to check for codes, the code is than the starting point for an evaluation.

      I wish cars reported codes to the customer but they don’t and you can thank The U.S. Government and the Dealer’s associations lobbing for that.

      Without the code I really have no direction to send you in.


  252. Hi Justin, great resource! I have a 2004 Legacy sedan with a 2.5. It runs perfectly except that it pings lightly to moderately (detonates) when I accelerate up even the slightest incline. Also sometimes from a dead stop on a flat incline if I accelerate moderately to quickly. Mostly at lower speeds (25-45 mph). It does not do it at highway speed. It is also probably a little worse in hot weather. Sometimes it will disappear after a second, other times it persists until I get the rpms up higher. Is this normal for these cars? The check engine light has never come on. I should also add that the car only has 19,000 miles on it. It was an old man’s car, and was obviously not used much before I got it. I have used all different brands of gas, and high octane, but the ping still persists. I have a 1998 with a 2.2 which never does this, so I guess I am a little worried I might be damaging the engine. The performance and milage are otherwise perfect.

    1. You may have a faulty Knock sensor, in need of a logic update for the ECM ( engine Control module) a defective EGR system or have some coolant entering the combustion chamber.

      I am speculating on the most common causes, it is not good to allow it to ping it can cause long term problems with the engine.


  253. We had our 2005 Subaru in for its 160,000 mile service and timing chain. Our check engine light also was on. The service guy said the cable to the evaporator was corroded, which was causing it the CEL to come on. They said they could repair it or replace it — replacing was $600 so we said repair. A few days after having it home, the CEL came on again. Any thoughts you have would be helpful on this problem. $600 sounds expensive for a cable.

      1. I don’t know…what we’ve noticed since, though, is that the check engine light comes on after we gas up. We got a new gas cap, which seemed to solve the problem, but today when we gassed up, the check engine light came on again soon after. Is there some secret handshake you have to do after tightening the gas cap to get the light not to come on???

        1. Ok,

          If the check engine light comes on there is a code set, without a code scanner you don’t know what code is set, without knowing what code is set there is NO WAY to know what system is indicating the problem, if the light comes on even right after fill up but sets a code pertaining to the air injection valve or knock sensor or the blinker fluid replacing the gas cap will do ZERO to resolve it.

          There is no secret handshake only the understanding that it is a complex system that will have a different meaning each time the light comes on. The average driver will never understand this, I have done the best I can in trying to state that the Gas cap is one possibility, but there are others..


  254. your site is wonderful ! you are extremely kind and of big help and I wish I could find a mechanic like you in my living area !

    best regards


  255. The first codes I got were misfire in 3&4, knock sensor and o2 sensor. I replaced knock sensor, o2 sensor, and fuel filter, after i replaced the knock and o2, I got misfire codes for 1&4.

    Idles just fine until you touch the gas and then it just acts sluggish, under load the car wants to stall until the rpm’s get to around 2500-3000. Bad plugs and wires possibly?

    1. Its possible it just needs plugs and wires but there are other possibilities as well.

      You can try the plugs and wires your self and see what happens or you can perform testing to determine exactly what is wrong. Its really up to you how you want to go about it, use nothing but the correct NGK Platinum Spark Plugs Part Number NGK 2300 and good plug wires I would suggest the NGK as well.


  256. Hi, after reading all the comments here I hope I can find an answer to my problem. My friend has a 1997 Subaru Impreza Outback Sport, and he has the Check Engine light on for a long time now… I offered to find a solution (Since I’m studying Auto Mechanics), and I took it to my school, were my teacher plugged the device used for diagnosing the engine.. It came out some errors that had to do with the Oxygen Sensors. I checked with my friend and he told me that he changed the sensor once. But then I find out that this car has 2 Oxygen Sensors (One after the Catalytic Converter and one way before it). So Our guess is that the Oxygen Sensor is the problem. I just want to make sure before I proceed to remove that sensor and replace it with a new one that it is the actual problem… Also, what tips would you give me on how to replace it (Especially for how long should I test drive it after I install it, and if it’s okay to unplug the battery to do this…) I would really appreciate the help given, and I wish it can be as soon as possible… Thank you!


    P.S: The car has been running fine since after the light came on, but there’s just one thing that’s wrong… When you stop, you can smell the gasoline coming out from the exhaust… I hope this helps!

  257. Wow! I have been a Subaru owner for 17 years, and this is the first time I have come across this site! What a great resource! Thanks in advance for your time!

    I have an ’05 Outback with 87,000 miles on it that was showing a CEL (& cruise flashing). I took it to the local Subaru dealership, where they ran diagnostics and found nothing to be wrong, so they “turned off” the CEL. Exact wording on the invoice was ” scan code P04020 Converter Code, ran graph on test drive and passed all test. Cleared Code and ran test, passed”. (I took this as they scanned for codes, but found no errors, so reset the system and re-scanned for error codes but found no errors). $80 later I was happy that there was nothing major wrong with the car. The service manager suggested that a very small “hiccup” in an o2 sensor or some other part of the exhaust system could have occurred and that the CEL can only be turned off after a system diagnosis (it won’t turn itself off even though everything is now OK). Less than 24 hours and 50 miles of driving later, the light is back on. I didn’t get gas since it was looked at (so am fairly certain it’s not a gas cap issue). I was near the dealership when it came back on, and stopped in to let them know it was back on and to see if they could look at it again. The service manager suggested that it may be the converter. Wouldn’t there have been a code that would have indicated this in the diagnostics that they ran yesterday? I’m wondering if they ran only an emissions test and not a full diagnostic? I am curious as to what questions I should be asking before they hit me with a $1800 suggestion of replacing the converter. I would also add that they said that my car passed the “test” after a test drive, but my “in” and “out” mileage are recorded as the same on the invoice! Without going into detail, I have had bad luck with service at this place, but it is the closest Subaru dealer and others are 1 hour+ away. Can you educate me in what I should be asking them to check next? Is there something else that could be setting this off that would not be an error code? My car seems to be running fine. Thanks for any advice you can offer. Thanks for any insight you can provide! 🙂

    1. There is one way to diagnose P0420 and one way only! 90% of the Techs out there have no idea how to actually diagnose the issue properly. It is one of the single largest misconceptions in my industry that the Dealer is the expert, its actually just the opposite in many cases.

      You can read here

      I can almost guarantee the service department did not go to this length and as such the diagnoses was incomplete which is why your car wasn’t repaired.

      The instant they “turned off” the light they also reset the catalyst monitor to NOT READY status meaning the computer is not looking at the catalyst function until the monitor is back on line which is a bout a particular drive event known as a drive cycle. Once the monitor for the Catalyst is back to ready status the catalyst function was looked at by the computer and it didn’t like what it saw in results of testing so it set the code 420 and turned on the light to alert you there is an issue.

      I would suggest the Catalyst has most likely failed but would need some data to confirm.

      Best of luck to you


  258. Hello,

    I have a 2010 Subaru Forrester. Today the check engine light appeard along with the cruise light which continues to flash. Please advise.

  259. My 17 year old just bought what we will call a beater car….a 1994 station wagon. Engine was replaced with a 175,000 mile engine. The CEL came on at the lot, code was misfire in cylinder 3. Cleared the code and we took it for a drive. No code came on. This car will be driven about 10 miles a day and for $1,000 not much can be expected of it. Drove the car home and sometime during the 30 minute trip the CEL came on again. I don’t have a code reader but would guess it is the #3 cylinder.

    He just brought it home tonight and haven’t done any tune up things like wires, etc. For his sake I’m hoping it just needs a new set of plug wires, that #3 is arching.

    I’m lucky. My car has a built-in code reader. If a CEL is thrown, I can press the VCM and get the code, look up the code and fix it.

  260. I have a 2005 Outback LL Bean, H6 engine, 40,500 on the odo. I have had a recurring problem with a burning or hot ‘rubber’ smell, that will occur when the car is on a long up hill grade. Usually the car has to downshift to keep the RPM’s up. I have had the O2 sensors replaced, and the cats replaced (at different visits). The O2 sensors broke when the Subie mechanics were trying to remove them. I know the cats get hot, but the dealer can’t seem to explain what the bad smell is from. After several months, the smell is back and I think the dealer is going to give me the run around. In addition, the check engine light is on and I have to get that looked at. The CEL was on a couple of weeks ago, but I think it was related to the gas cap. It finally cleared, but, now 2 weeks later it has returned and I have not touched the gas cap. Something else must be wrong. Any suggestions?

      1. I got a P0442 code (per dealer) O2 sensor failure. They tested it and said it was within spec and cleared the code and gave me the CA smog cert that was due. It was suggested that if the problem returns, then I should replace the O2 sensor for about $350. Aren’t the O2 sensors under the emissions warranty? I am worried that they might break it trying to get it out (that happened once before) and I’d have to pay much more for the extra parts.

        1. PO 442 is Evap emissions (small leak), there isn’t an O2 sensor in the world that will fix that code.

          Not knowing model, year or mileage its tough to say if there is a warranty issue.

          The 02 sensors are also covered under the 3 year 36k warranty only unless you bought a extended warranty. All of this and what is covered by the Federal emissions warranty is in fact covered in your owners manual.


          1. The car is an 05 OB LLB edition, H6, 42,200 on the odo. Cats and O2 sensors replaced previously (13K). The dealer invoice states, “Oxygen sensor failure. Tested Oxygen sensor (s). Working properly. Cleared control unit. System working properly at this time” Your comments seem very different from what I have been told by the dealer. Do I need a new mechanic? Do you make house calls?

          2. Either you have read it wrong or they made a typo in the code number. P0442 is related to the Evaporative emissions system.

            O2 codes would be P132 133 134, 135 etc its a federal law all manufactures have to adhere to the P0400 series is Auxiliary Emissions type systems.

            Google OBDII codes and research it your self.

  261. Justin,

    Thank you for all the great advice!

    Not sure you can do much for me as I don’t have the code but I’ll explain anyway…

    About a month ago, after returning from a four hour drive, I noticed smoke coming from the front of the engine. Took my 2005 Outback 2.5 to the dealer (as it’s still under the extended warranty – 83k miles) and they found that the CRV boots if the front were cracked and throwing grease onto the manifold which was causing the smoke and burning smell. After having them replaced, a tune-up and oil change, I thought everything was fine. Then last night, one month later, the check engine light and flashing cruise came on.

    I’m taking it back to the dealer tomorrow to have it checked but was wondering if there’s any connection between the grease being thrown on the manifold and the light now coming on? Sorry I don’t have a code for you to work with.

    Thanks for any help!


    1. Hi Dan,

      They wont be related. And yes with out a code there is no direction.

      The check engine light comes on only when the Computer sees a problem with a sensor, control device or the presence or lack there of of a system monitoring device indicating a system that is no longer functioning properly.

      I am not sure what kind of Tune up you had There aren’t any specified by Subaru other than the 30/60/90k services but there again there is nothing to “tune”, its just an archaic term that I try to point out that shouldn’t be used with modern vehicles and really only adds to the confusion about what type of services you might be paying for..

      The check engine light is also mostly about the vehicles emissions system and not about the engine, look to your federal government for this inefficiency.

      You can also read about the light and its causes in the Owners manual

      Hope that helps


      1. Justin,

        Thanks for the info.

        It was in fact the 60K SERVICE that was performed, not a tune-up!

        In looking through my paperwork, I found a Service Program WVH-18, Engine Control Module Reprogamming letter for cars registered in CA, MA, ME, NY or VT, which was sent to me from Subaru in June 2009. The letter states that under certain driving patterns the catalytic converts may devolp high internal temperatures that ‘exceed the design parameters. This condition may eventually degrade the effciency of the converters (The check engine light will illuminate to alert you if the converter efficiency has degraded beyond an acceptable level…”
        I took the car in and had the reprogramming done in July 2009, but I’m just wondering if this may be related in some way?
        Just thinking out loud (since without a code there’s not much more I do!) and throwing this info out there. Since you’re located in WA, not sure if you knew about this or not.

        Thanks again!


        1. Hi Dan,

          The check engine light can come on for a loose gas cap, a failed catalytic converter , a defective sensor and a thousand other reasons.

          The light coming on now wont be related to the reflash that took place in 2009, its possible that another reflash is needed for something else, but its also possible there is just something new that came up. The electrical items in your car work in the same fashion a light bulb does and are subject to the same rules of failure. If control device or solenoid has failed to function or an 02 sensor is no longer as active in sampling rates as it was when its was new the check engine light will come on.

          It sounds like not knowing is bothering you a bit. I suggest you look into purchasing a basic can bus compatible code scanner so that when and if the light comes on you can at least scan for codes.

          Here is a link to one that I happen to like


          1. Thank you, Justin!

            You can tell that the not knowing IS bothering me. I’ll invest in a code reader and let you know what I find out from the dealer tomorrow. I’m praying to the Extended Warranty Gods that whatever it is will be covered!

            Thank you again for all the helpful advice!


          2. Justin,

            Just wanted to give you an update on my check engine light…

            Just heard back from the dealer that both catalytic converters went out. Thankfully when he called, it was to tell me that the car was ready and that these were one of the few parts that was covered under the extended warranty so they went ahead and replaced them. Big sigh and thanks to you (for all the advice) and to the Extended Warranty Gods (who are still watching over me!)


  262. Hi Justin,

    Here’s my code: 0325 (misfire cylinder 1) on 1997 outback

    Had the head gasket replaced twice a couple years back… first time not sure but second time RHS only (not side with cylinder 1). check engine came on about a year back, and I just assumed it was head gasket again since outbacks 1996-99 are known for that.

    Last weekend I checked the wires by swapping cyl 1 and 3 wires – still got 0325. Replaced the spark plug on cylinder one – the old one: although the tip was dry, the gap had gone way up to .0053″ (maybe missing a zero there).

    Initial results were good, check engine was off when I started the engine and on subsequent short (6 mile) trip including a stop at autozone half way through.

    next morning, the CEL was back. I reset it while I’m driving with my code checker and notice that it tends to turn on right after experiencing hesitation (likely due to misfire) in acceleration, which usually happens if i accelerate quickly or on a grade. I smell faint burning oil (what I’d call normal for a 14 year old car) when I park (likely slight oil leak) – it’s not detectable while driving. Note the coolant temp is rock solid in the middle, no variation when misfires occur.

    2 questions – does this sound like the head gasket again? does the increased gap mean anything other than an old plug? (it was fairly low end, and about 1.5-2 years old).
    Second is there a way to disable the knock sensor so I can pass my smog check? 🙂 Last time my measurements were all way below limits, but CEL on forced a retest and cost of replacing the EGR valve)

    1. Well Jeff,

      PO325 is not a Misfire Code, I would stop using whatever code scanner you have and buy a better one.

      PO325 pertains to the possibility of a failed knock sensor, problem with the circuit or ECM.


  263. Hi Justin,
    excellent website, first of all.
    I purchased my 2005 Subaru Impreza RS two years ago with 42,000 miles. now i am up to 73,000 miles. when i got the car it had this very slight chatter when accelerating or climbing hills, or maintaining speeds on the highway. Until very recently i thought this noise was some sort of bearing, but now i understand that it is spark knock. i searched some videos of cars with spark knock to compare the sound, and that is definately it. now my spark knock is extremely noticeable once i’ve been driving for a little bit. the noise is especially pronounced on the highway, climbing grades. i will get the noise at slow speeds climbing hills as well. i can control the knock level easily, and sometimes the noise changes from a chatter into a much harder chatter(at which point i would turn cruise control off or reduce/increase throttle) i’m currently at college, but once i go home again i will replace the knock sensor pronto. i have continuously used marvel mystery oil as a fuel cleaner, with great results. i replaced the plugs recently as well. my question is: why isnt my check engine light on? there is a clear spark knock, and i have maintained it very well, and used a fuel additive in the proper amount, continuously. i also have a scangauge2 hooked up to the car, i plan on watching my ignition advance readings while the knock occurs, as well as watching the readings while i tap next to the sensor with a screwdriver. Is it possible for the sensor to go bad, with no CEL?

    Thanks so much,

    1. You wouldn’t have a failed knock sensor on a 2005 model.

      Without a Subaru Select monitor graphing data there will be no diagnoses only guess work. There is a limit to what you can test with out one.

      As far as no light, its one of those situations where the amount of knocking correction is not triggering a fault code. The possibilities as to why are numerous most likely the ECM is defective, that doesn’t mean rush out and buy one just that it needs to be evaluated.


  264. i bought a Subaru B4 Twin Turbo legacy 1998 model.Recently it started to loose power and gains the power while im driving as if im running low on gas.And also whilst im driving it shakes as if the gas is closing.What might be the problem.i thot it was fuel pump and i replaced it and keeps doing the same.The engine check light is on after replacing the fuel pump.

  265. Hi Justin, I have a 2000 Subaru Outback. Had the car for about 6 mo. I did the timing belt, water pump, front 02 sensor, new alternator,battery, PCV valve, air filter, cleaned MAP and IAC valve. I haven’t replaced plugs and wires yet because they looked okay. The car is throwing a 0420 signal and a 0107. Cat system and MAP sensor respectively. It will idle low at times after warmed up to the point of vibrating around 500 RPM. It will stay low but has only actually died a few times. The 0107 goes off usually when the car is decelrating from Hwy speeds and shudder and dies sometimes but not always. Then the CEL will come on and AT light will flash but resets. What’s my next move? Other than a shady authorized dealer here in SW Mo. I don’t really know who to go to for a good Cat test. And the MAP sensor thing is just confusing. I understand what it does but so far nothing is working. Should I go ahead and replace the plugs and wires as well, maybe the fuel filter? Any help would be appreciated!

    1. The map code is most likely a result of the low idle not the other way around, the Catalyst code is most likely a failed Cat.

      With out data there isnt much I can offer, if its a 5 speed it could have a failed “n” switch but there are so many other possibilities I hate for you to get into a parts toss.


      1. Sorry it is an automatic. Is a back pressure check a good enough Cat test? I don’t trust the Subaru dealer here at all. It is a large multi-car dealership that is famous for being dishonest. And no Subie specialized indy shops. I will probably have to rely on them. Any advice on what I should look for, or have them check when I take it in for a good overall scan. I’m not even sure which shops would have the software to do it correctly. I’m afraid of getting screwed because someone doesn’t know Subarus.

        1. Back Pressure does not correlate to function only confirms restriction.

          There are a few different Catalyst tests that can be done but all require the proper test equipment and the skills to use them.

          The most common method is graphing data with the select monitor you can read about it here.

          I am sorry that I cant help more, but there has to be a good shop somewhere near you?


  266. hi !
    mine is a Subaru outback impreza sport 1998;
    when I plug the OBD II, it reads as follows:
    fault: 2; pending : 0
    fault 1 : PO 325 book : (knock sensor 1 circuit malfunction bank 1 or 1 sensor)
    fault 2 : PO 440 : book : Evap emission control system malfunction

    my question : is it serious ? or I can carry on like this ?? I may think it is only a problem of polution (PO 440) or could it be possible that the Subaru is more thirsty ?? (because of this malfunction) a friend suggest that I should put Super gas to resolve the PO 325, as I am just filling the car with regular unleaded right now; what do you think ?

    thanks a lot !


    1. Super gas wont resolve a failed knock sensor.

      Most likely it has a failed knock sensor, very common but the circuit should be tested to verify this. Possible ramifications are overall longevity of the engine and reduced fuel economy if not repaired.

      To the P0440 either the Gas cap is faulty, the system has a Evap leak or there is an electrical issue.

      Hope that helps

  267. Justin, I am basically at wits end with my 02 Legacy gt, 2.5l. The car is a 5 speed manual, when I put it into first, and go to accelerate the car will bronk and buck violently then at a higher rpm in first will finally accel to about 3k then I shift, into second and the engine idle is really rough. It seems as if when cruising at 30-40mph and I go to give gas, it seems like the engine goes to an on or off switch meaning there is no in between acceleration..While stationary if I rev the rpm, it will dip so low then sometimes stall..I believe I had the p0305 which was the IACV..I replaced that, ran great for a week or so, then it is back to bronking and bucking. I ran seafoam, injector cleaner, still no fix. The IACV is not dirty whatsoever..I am also not getting any other codes…the cat was replaced as well as new o2 sensors..does this sound like an EGR. MAP, TPS issue? Thanks for your help!

    1. P0 305 is cylinder # 5 misfire, which doesn’t exist on a 4 cylinder Outback.


      Sometimes you can take care of an issue your self and sometimes you need a pro on your side, it sounds like the latter is where you are at.

      I can send you on half a dozen wild goose chases and you can spend money on parts, but what you really need is to have someone local to you do a real diagnoses, not a code scan not a guess but evaluate the systems and figure out whats wrong. It does cost money but what other real choice do you have?


  268. Very helpful site. Justin is most effective when he answers the questions directly without preaching the need for professional diagnostics. People would not be here were they not in need of a professional opinion. Still you deserve kudos; I would take my scooby to your shop. Keep up the good work.

    1. The problem is that each situation is different and some instances require expertise. That is why some can be answered and some need help, also I try to get a sense for the skill set of the questioner, and not everyone is cut out to make their own repairs. This starts with listing codes that don’t exist for their model and continues on with a real lack of understanding about OBDII. When I get posts about someone not wanting to get burned, I understand that and do want to help, but there are just as many who just don’t want to pay to have a diagnoses done.

      Some codes are easy and straight forward, others Require Data to diagnose, the data is typically only available by graphing with a Subaru Select monitor and laptop or equivalent.

      When you go to a Doctor, sometimes he or she has to defer to tests to make a diagnoses, the same rings true for your car in some cases.

      We live in a world where a check engine light comes one time as a loose gas cap, and another time minutes before the car leaves you stranded, the information to the driver is the same.

      I have a doctor that I call and make an appointment o see when I am above my ability to figure out what is wrong with me, anyone who ones a car or a house or a dog that doesn’t practice the exact same principle is bound to be frustrated.

      Those that want to do a lot of their own repairs have that right, and we have many customers that only come to us when they are above their Scope or Skill set.

      I try to help everyone, but at the same time cant and wont completely devalue my profession as a whole to help a few. Sometimes the best advice I have is to establish a relationship with a good service provider they exist in every state the Market place demands it and use them when you need to for some that’s every instance and for others its just once and awhile.


  269. hi all

    well I had my CEL on last week and brought the Subaru legacy GT to a Subaru certified mechanics here in Montreal quebec. I bought the car in California, and the 4 years I lived there she has never experienced the canadian winter. She did great for the 3 first years here in quebec until the CEL lights on. I have 160K miles on it.
    As the major tune up was due I did that and they replaced spark plugs, cover gasket seal, all the fluids and coolant, filter…. But still the CEL was on. so they went into a sorrow inspection and after replacing fuel injector in cylinder 1 (only 3 cylinders were working), a wire, knock sensor; the car does not have the CEL anymore.
    I had code P0325, and i guess two other ones for the wire and the injector.
    My point is that the certified mechanic did a good job, and the car is driving like new or almost as it is 11 years old. I has a cost though as I spent 2000 dollars. THe major tune up cost $1000 alone. It is the first time the car gives me major trouble, but I hope she’ll be driving for 100K more ti finally go to Subaru heaven.

  270. Justin,

    I have a 2007 Forester with 65k miles. The solid check engine light with blinking cruise light. I had the gas cap replaced and reset the system. Lights came back on. Dealer says its a fuel tank roll over valve. About $500 to replace($90 part-4hr labor). Any suggestions? thank you

    1. My suggestion is to fix it.

      You should also ALWAYS know the code number set when the check engine light comes on, that way if the light comes back on later and its the same code number you know there is still a problem with the same system. If the light comes back on with the different code than its a different system this time that needs to be evaluated.


      1. Sometimes I wonder about all the computer monitoring that goes on in modern cars. If you put a space shuttle type monitoring system in a car it would run a lot more eco friendly. Is there a point that we have too much monitoring.

        I’m currently running down an intermittent code 400 on my son’s new-to-him 95 Legacy wagon car. It runs well, gas mileage is great and would rather the code be a component code.

        The car lot that sold the car put a replacement 2.2 engine in the car and I am suspecting a possible electrical condition. Although that EGR valve was caked with carbon unlike any I have ever seen. IMHO some of the vac ports are way too small and are apt to get clogged with carbon. All of which cost people that know nothing of cars, far too much money.

        I am really enjoying working on the Subbie because of its simplicity. Compared to my over engineered Jag the Subbie is wonderful to work on. But I do wonder about putting all those sensors, etc. under the intake. The engineers must have had small hands. 🙂

        1. We achieved above Space shuttle status in the mid 90’s when GM came out with the P6 processor.

          The average driver has no idea how complicated a 2011 vehicle has now become.

          We are at very low levels of emissions with multiple emissions systems and monitors for each of them to get there.

          “But I do wonder about putting all those sensors, etc. under the intake. The engineers must have had small hands. ”

          Those components were put on the intake before it was installed on the engine and before the engine was installed in your Subaru.

          P0400, start with testing the transducer for the EGR.


          1. Yes I know they were installed before installing the intake, I was really referencing those future owners/shop people who must get at them.

            The transducer was my first check because apparently they are the first culprit and it tested well.

            One thing I have yet to replace is the EGR valve gasket. After cleaning out all the EGR gunk, cleaning the throttle body, installing new vac lines, etc. I didn’t have a gasket on hand. I now have one in hand but want to be sure that I won’t again need to remove the EGR valve before installing it.

            I’ve been thinking about getting a smoke test but I’m not yet to that point. SOmetimes the problem is staring you in the face…ya just don’t see it. I remember one time I changed engines on one of my Jags. Buttoned everything up but it wouldn’t start. Two weeks later and by luck I saw the bundle of ground wires on an eyelet that had been stuffed down when I dropped in the engine. I immediately knew what they were and were they were to be attached. Attached them and the engine fired up. They were the ground bundle for the injectors.

            So I am in the looking stage of the P400 code.

  271. Hi Justin,

    I’ve owned my 01 Subaru Forester GT for about 6 hours, and now it won’t drive. The check engine lamp is on, and the car starts but it won’t let me get the revs up. It’s like it’s in some sort of ‘limp home in on idle revs’ mode.

    I’ve got to take it to a dealership here in Australia, but would like to have a better general idea of a possible cause.

    I thought I heard the sound of a hose releasing air while driving it earlier but couldn’t see anything obvious when i looked under the hood.

    any thoughts?


    1. Hi Andrew,

      There isnt anything I can offer you from here. Without first hand knowledge of the exact symptoms plus a visual , audible inspection under the hood plus some data from sensors its all just a guess.


  272. Hello,

    I have an ’02 Legacy B4 Twin turbo bought in Japan(84,000 km or 52,200 miles) that has been acting crazy, something never experienced with any other vehicle. In the past, it had trouble starting in the winter and the dealer replaced the fuel filter which seemed to fix the starting problem, however it had this weird shaking side to side (barely noticeable at first) initially and then it would subside. Its been 4 months since the fuel filter was replaced but now the shaking is more prominent at startup and when you try to drive with the a/c on, it shakes violently and if you try to accelerate, the transmission light/ check engine light blinks (never stays lit) and it feels like its about to stall, however when you shut the a/c off it drives fine. I’ve also noticed the rpms at idle are about 150 to 200. I spoke to this one guy and he thinks it maybe the idle control module that needs replacing which could run about $1000. He said others have had this problem with their legacys too. Not sure if this has anything to do with my current problem but I also want to mention, in the past there was a fuel line leak up front which was found and fixed. Any help or info would be most appreciated.


  273. Hi Justin,

    Thanks so much for offering this very informative forum. I have an 2008 Outback Sport with <20K miles.

    This past weekend I was on a highway following a slower driver. The cruise control was "on" but not engaged. We were going approximately 60 mph. I pulled into the oncoming traffic lane to pass, and upon stepping vigorously on the accelerator, the car lost a lot of power and was unable to accelerate at all. The traction control light came ON suddenly (meaning TCS was now off). And the CEL started to flash. I do not believe the cruise control light did anything unusual. I pulled back into my original lane, pressed the traction control button to re-engage it, and the flashing check engine light disappeared.

    Any idea what could have happened? The car has driven normally since that episode (the only time) with no unusual warning lights.

      1. Thanks so much for your expertise. Do you have any more specific info regarding the logic reflash I can provide the local dealer? I just spoke with them over the phone here in Portland and they were a bit baffled. Since the warning lights are off and things are running normally, they said it would be hard to pinpoint things. I did have the most recent ECM recall reprogram issued to a lot of different models this past Spring.

        I may try to reproduce the situation, only not into oncoming traffic this time =).

        1. Hi Wayne,

          There is a TSB floating around about the issue its a year or two old so its probably not fresh in their mind.

          That’s also the game they play, even if I give you the Pack number they still want to charge you to look at it.


  274. Justin… Hello and HELP!!!!
    Daughter has a 1999 Sub Legacy that has been a nightmare lately.
    By her own fault and some bad mechanics advise she has had to replace the tranny, rebuild the engine/ rebore heads, and recently again rebuild the tranny. On top of that almost everything under the hood has been replaced over the last 2 years. But……
    we keep getting a CEL going off.. the codes read Knoc sensor which was replaced. Then a week later it again went off again reading knoc sensor but this time they found a partially cut through spark plug and so replaced all that. Now a month later, CEL went off again, this time the Pep boys techs say its the catalytic converter ( not sure if they got a P0420 orP0430 code).. Car has been running like a dream – no hesitations, idles ok, good gas milage
    from reading some of the above posts.. I pretty well doubt they did more than just code read and looking at a $5-900+ job again for this car based on just a code # doesn’t seem to make sense from what I’m reading.
    She can’t afford another big repair like that nor to replace the car yet. The Techs told her its ok to just keep driving the car until next June when her inspection is due….. since this kind of mechanics advise from other folks is why we have replaced 2 trannys and an engine.. I’m a bit skeptical at this point.
    Any ideas or suggestions?

    1. If it setting a po420 than most likely it needs a catalytic convertor replacement.

      Based on what she has had o put into the car , I would invest in a code scanner for here to learn how to use( which is very simple) and put off the repair until absolutely needed. The light will continue to come on, but this way she can read the code herself to make sure its not something new occurring as there is only one light and hundreds of fault codes and even more possibilities of why.

      Here is a link to one that I like

      I do sympathize with the amount she has had to lay out in repair costs and thin that based on the code you are telling me about its ok to ignore for now, but I do strongly suggest backing that up with a code reader to leave in the glove box and scan it herself to ensure she is never stranded.

      Hope that helps


      1. Thanks Justin.. that’s one of the suggestions I gave her.. if she chose to run the car just keep checking the codes to make sure it wasn’t something else going bad.
        Funny thing.. yesterday the light turned itself off and hasn’t gone back on…??? Not sure why or what.. could it be maybe a plug? She has a tendency to run the tank down to a whisper of gas and I have been wacking her upside the head about NOT doing this due to junk in the bottom of the tank ( or is that an old wives tale?)
        Before we replace the converter ( if this light comes back on with the same code) I have told her it sounds like it might be a good idea to drive to your shop for a second opinion!
        Thanks so much for the above advise and any other ideas you can give.. so glad I found this site and appreciate what your doing to help folks like us!

  275. Hello Justin,
    This morning when I started my 2001 Subaru Forester S it ideled rough – like one or two cylinders were not firing. CEL came on flashing. I checked the oil and at first it was a little low but second check showed normal level. I did notice tini bubles in the oil. Also the coolent level is low. I pulled two of the spark plug wires and notices a little bit of oil around the rubber. Don’t have engine codes yet. Any ideas what might be going on? Car has just over 101,000 miles on and up to this point was working great.
    Please help.
    Thank you in advance for your time Justin! Really appreciate any advice you can give.

    1. The flashing check engine light indicates a cylinder misfire and the Subaru needs to be repaired ASAP and not driven until it is repaired, you need some basic tools such as a code reader to know which cylinder is acting up by using the codes set as a starting point in your Diagnoses. A common thing would be oil soaked plug wires causing cylinder misfires you could do at least a visual inspection, but the repair would be to replace the plugs, wires, and reseal the spark plug tube seals and valve cover gaskets. If the plug wires are not oil soaked you would need to look else where.

      You will than need to diagnose whats wrong, this can be as simple as a faulty spark plug or spark plug wire or as expensive as a bad valve. Not everyone is up to the task or diagnosing and repairing this situation, and if not you would be best served to seek out some help local to you. With out the code number I have no where to send you to start out with, if you buy plugs and wires and it doesn’t change anything you have us spent money that you didnt need to.

      Hope that helps


  276. my 05 sti is giving me serious grief. When I accelerate up to speed, it feels pretty much normal. When Im cruising (no matter what gear it is) it FEELS like the brakes come on. Or cuts power for a second. Im sitting there and body rocking every 2-3 secs. Its frustrating, annoying, and basically inoperable

    It went in for a timing belt change (99k) on tuesday. The dealer ran the “check engine” and it came up an 02 sensor. They cleaned it, but its not fixed. I trust them totally, but im thinking maybe its combined with something else. Ive had an 02 sensor go out on a WRX and it wasnt noticeable.

    Its turning into a money dump. Clutch two months ago $1500, timing belt $614, the sensor about 100-300$

    The turbo pegs at .1 or whatever. the gauge goes to .15 I believe. bad turbo? It drinks oil, and when I checked coolant, I noticed it was low…this all started happening when I bought another car for daily driving. Needy car. Any input would be appreciated.

    1. Yes an STI is a very needy car, its a Performance vehicle, and I have never come across one that didn’t get into your wallet. I am sorry if you were previously unaware of this, but you can expect to put $$ in a performance car and on a STI right at about the 100k mark.

      I cant offer you any real advice on your Symptoms with the amount of information you have provided me, if it was diagnosed with a failed 02 sensor and merely cleaned as an attempt to repair that may be the best place to start.

      The STI is typically reliable but at the mileage it has its ready for a round of service and repairs to maintain that reliability.


  277. Justin,
    What if there is no CEL that comes on and you get in your car one day and it wont start? This past monday morning I got in my 05 Legacy GT w/ 79,000 miles. When I turned the key it acted as if the starter engaged for a second then disengaged and made the typical motor winding sound. I tried it several more times with the same result. So I reluctantly called my local repair shop and had it hauled over for what I thought was possibly a bad starter. The mechanic went out to check it to see what it was doing and when he did, it started right up… WTH!!! He said that when it started it ran as if it had been flooded for a minute or two then cleared up. Throughout the day he drove it around and started it about 20 times and said it “appears” to be ok. I’m guessing your going to ask me if he pulled a code on it…the answer is no. It’s a small shop that I trust with my other cars but they don’t have the tech to pull codes on a subaru. So my question to you is, in your experience have you seen anything like this and do you recommend I get my car into my subaru dealer (who is an hour away) and have it checked out properly?

    1. Hello Louis,

      Its very possible it was just flooded? And the Computer has now way of detecting this so it cant report the issue VIA a check engine light. I will tell you that this comes up at the beginning of every Fall and winter however.

      Here is why.

      The worst thing you can do with a horizontally opposed engine is start it up , let it run for a few moments say to move it out of the wife’s way or run back into the house after something you forgot. May times when you try to restart it, either moments later or the next day that engine may in fact be flooded as there was just to much fuel that entered the combustion chamber and was not burnt.

      When the temperatures come down this issue is made much more pronounced as the computer feeds a cold engine much more fuel.

      On an inline engine or a V design the excess fuel will literally pool on top of the pistons and will slowly evaporate. But on a H engine the fuel actual collects on the cylinder walls, which will diminish the ability of the engine to build compression as the friction needed by the piston rings making contact with the cylinder walls. With out compression there is no explosion all while the computer is adding more fuel to the “no fire”.

      The right thing to do is to floor the gas pedal while trying to start a flooded engine as it will do two things one is increase the air coming in, and second is to put the engine into “clear flood mode” by shutting off the injectors.

      I dont know if this at all fits your scenario, I also would have suggested the Tech pull codes as most likely there wouldn’t be any unless your check engine light doesn’t come on because someone removed the bulb?

      Dont see a lot of no starts on the GT models that aren’t related to low or no fuel pressure, I would suggest that maybe a fuel pressure test should be performed if it wasn’t just a flooded situation based on what I tried to lay out earlier.

      Hope that helps


  278. Justin,
    I have very little knowledge on cars so please bear with me… About a month ago, my fiancé attempted to start our car (1995 Legacy wagon) shortly after turning it off. It sounded like it was going to start but never actually turned over. He tried this quite a few times until the cat’s attempt at starting no longer happened and all he got was a “click.” We had a local mechanic check it out and they replaced the starter. It worked fine after that for about a week. Then it would occasionally stall while idling. (did this about 5 times over a period of about 2 weeks) we had it checked by another mechanic because the CEL was flashing when we received it back from the first one. Turns out they had forgotten to unplug the diagnostics cord. The second mechanic said there was nothing wrong with the car. Three times in the last two weeks (after getting it back from the second mechanic) it refuses to start just like it had in the beginning. It sounds like it’s going to but doesn’t actually turn over. We usually sit and stress about it, weighing our options, for about 5-10 minutes and then try it again. Eventually it does start for us (so far) but the CEL comes on after it starts. We intend to get the codes read on it but every time we have the opportunity to take it to autozone the CEL has turned itself off. Any suggestions or ideas would be very much appreciated.
    Thank you!

    1. Hi Mary,

      Sounds like this has been Quite a ride!

      The code will stay in memory even if the light goes out for a period of time depending on what system is affected, so it may still be wise to run it by Autozone the next time the light comes on even if the light goes off the next day, I do have to point out that Auto zone can give you codes and may guess right, but cannot actually diagnose the car. The “click” no start and the Check engine light don’t have anything to do with another.

      Really it just needs to find its way to a good Subaru tech, or it will be more of the same I am afraid. It could be that the starter is defective, the ignition switch worn, it could have a faulty sensor causing the intermittent check engine light as well.

      I dont understand what diagnostic cord would have been left plugged in unless he was referring to the D check connector, which by the way there would have been no reason to connect to diagnose a “click no start”

      As far as the staling that’s also probably not related to the starting issue either.

      I know that it all probably seemed like it was fine until the first no start and that it should of only needed one thing to correct it, but sometimes multiple issues can crop up during similar time frames.

      IO wish I could solidly point you in any one direction but its just not possible with out seeing the car first hand or having some data such as a code number or ISC percentage.

      Sorry I cant offer more


  279. Hey Justin, I have a 98 impreza 2.2L and my CEL just came on today. It was cold this morning so I started my car to warm it for 5-10 mins then drove to work (5min ride). When I was parking the car felt like it was going to stall, but it didn’t. Fast Forward: leaving work I started my car but it stalled a few seconds after it started. I started the car again and slightly gave it gas when it felt like it was going to stall again. I held the engine at about 1000-1500 for 20 seconds or so and the engine seemed fine but I looked and saw the CEL was on. I drove home and did a visual check of the engine bay and saw nothing obvious. I did hear the air intake sound like it was working pretty hard so I shut the car off and checked the filter and it was very clean. I restarted the car and it was still weak sounding and when I held the engine at 2500 rpm the sound was not smooth it faltered as I held the gas.

    When I purchased the car used I had the plugs and wires replaced, fresh oil change/filter, fuel system cleaner, oil restore treatment, new air filter, brakes replaced (rotors, pads, drums). I have maybe put 1,000 miles on it in the past year.

    Any ideas?

    I’m going to try and have it hooked up to an OBD II scanner this weekend to try and diagnose a little better but any help would be appreciated.

    1. When you get the code number I may be able to provide some insight but there is not much I can say without the code number and then really its possible that it wont be enough to offer much help either.

      Sometimes data from sensors is also needed to offer much in the way of help. Generic OBD scan tools dont always offer this.


  280. Great site sir,

    Had a 86 justy in the Navy in the 80’s loved it…had Toy’s my entire adult life…02 Tundra with 123 K on her…but gas is killing…so I went back and searched for a Forester because I wanted AWD and 4 cyl on a good car…found one wholesale…took it home…CEL comes on..took it to Auto Zone…air intake code came up…dont have it in front of me to tell you exactly… But I see that others have had this problem so I went and purchased CRC MAF cleaner and started cleaning components…and the entire air intake system…car was running fantastic..quick…no hesitation…after that cleaning this morning it will go and then sputter…and rev high to about 3000 rpms and chirp and the AT Oil light came on…it has a K & N filter…Now I thought it had a MAF but another person told me it might not so what did I Clean…they asked for pics of it..unfortunetly I work midnights…so I will have to take them tomorrow….I am very upset becuase I love that car already and it was riding great even with the CEL on… I will tell you I unscrewed what I thought was the MAF and sprayed the CRC on the component and put it back together… I hope I didnt screw it up…thanks. RJ

  281. Hey there,
    2005 forester 175k miles. CEL light comes on with the cylinder 3 misfire. replaced plugs, wires and coil. I know there is a leak with the head gaskets and working on the funds to fix that one. But not sure if that is causing the misfire or if it is something else. It runs just fine, but on occasion on start-up it idles a little shaky. after 3-4 normal starts, the light resets itself, only to turn back on in the next 1-3 start-ups. Suggestions here? All the techs are baffled whether or not the head gasket is causing this or if something bigger.

    1. Have the “techs” look at the Valve guides.

      Use the search feature on our website and you will find an article with a Video.

      There is no reason any Tech should be baffled with a Misfire. The internal combustion engine while it has gone though changes still uses the same basic principles for proper combustion.

      Were the plugs, wires and coil found to be faulty or was that a guess?


      1. it was more of a guess since they were cheap and the wires hadn’t ever been replaced. the plugs had been so we were more iffy on replacing them again. we borrowed a coil to test that before making that purchase and it still does the same thing. I’ll talk to them about your suggestion as well. I’m shooting for the cheapest fix so I can sell it. I’ve got a new 2012 outback on order.

  282. Justin,
    Stumbled upon your site and since I unfortunately have an issue with my wife’s 2007 2.5i I thought I would drop you a line:

    Situation: Car has 74,xxx on it and all maintenance is generally up to date (sans brakes). We recently moved down to Georgia from the northeast and during the last 3 hours of the trip the check engine light came on and the cruise light began to flash. The car felt as if it lost a cylinder (this is relayed from my wife as she drove the car herself). The light then went off by itself.

    A couple days later we had the car taken to a local shop just to have a check done and ensure things were OK. They found nothing wrong. About a week later the problem returned as the car was idling very rough and the CEL returned. We brought it back to the shop and they initially thought it was a misfire due to a bad coil. After replacing the coil they were still left with the misfire. At that point they ran a compression test and attempted to run a leakdown test a few times. They also swapped the spark plugs to see if that was the issue. Essentially at this point nothing in the realm of igition issues seems to be causing the misfire and they are convinced that the cylinder 4 misfire is either due to a burnt exhaust valve and / or lifter isse.

    They have quoted me $1,5xx plus machine shop fees for grinding the new valve. My question is given the mileage is this something that is even remotely common (i.e. burnt value causing a misfire issue?). This is my 3rd Subaru (I had a 2003 WRX and currently drive an 09 WRX) and this is the first real issue I have had to deal with. I am really disappointed that a car with 74,xxx may need to have a new valve at this stage of its life…

    If you have any thoughts I would appreciate it…

    1. HI Josh,

      Its not common for a 2007 to develop a burnt valve. That doesn’t mean it cant happen.

      No shop in the world should struggle with a misfire diagnoses if its acting up when they view it.

      A burnt valve will create low compression and at least 20% leakage to the exhaust, it doesn’t have a choice its a mechanical fact. It should not be hard to spot with low compression and leakage, thats the part based on your post I dont quite understand.

      Now if its a matter of who is paying for what kind of tests that’s different.

      At 1500.00 I fear the job is being quoted incompletely? It should be both sides, and you should plan on replacing your timing components while it is apart. May be the labor prices where the car is is a whole lot cheaper than where I live?

      Without seeing it for my self I really cant confirm the diagnoses, typically for a exhaust valve to burn that early it was overheated as per lack of lubrication or there is a exhaust leak close to the valve somewhere.

      Hope that helps


  283. Just came back from a trip taoday and after stopping my car then restarting it I noticed a lack of power and some rough idling. When I accelerated the CEL started to blink. The CEL was already on and when read recently it indicated I needed a new O2 sensor. I’ve done some research online and have come to the conclussion my engine is misfiring. IM bringing the car to a garage tomorrow to check it out, but was wondering where I’d start in the order of process of elimination. Just would like to fix as cheaply as possible as I’ve recently acquired this car and have sunk about $1000 into it getting it up to par such as brakes and cvs and one wheel bearing.

    1. Hi Shane,

      The process of elimination should be done by the shop doing the diagnoses. A misfire will cause a check engine light to flash, and it should not be driven when the check engine light is flashing. The 02 sensor is most likely not causing the misfire. This is why the code number is important when asking questions. The light is the indication that it needs to be scanned for codes, and then the codes diagnosed per the proper flow chart in order to determine why the code is set.

      Hope that helps


  284. Justin,

    Thanks so much for doing this site on your free time. It’s unusual these days to find such a goldmine of suggestions.

    I have two quick questions, if you’re able to reply. I have a 1996 Brighton, 300k km, and the CEL just popped on, and the only other thing I’ve noticed is the resting idle may be 200-300rpm higher.

    Tried to scan with an ‘Autoguage’ code reader (which works fine on other vehicles tested afterwards), but on the Subaru, would not register a problem code, also wouldn’t clear the CEL light, and finally wouldn’t read the other variables of the car, i.e., the various temperatures, pressures, etc..

    What do you recommend as the next step? Go to my trusted independent mechanic, Subaru dealer, try another code reader? Do you think this could mean the person i purchased it from fiddled with the computer, so as to hide an issue? The car runs like a top otherwise. I’d bring it to you, except I live in a different country!

    Thank you so much for time and thoughts.


    1. I would try another code reader, maybe if there is an autoparts store nearby?

      I will offer however, if the car wont communicate with the scanner, and the check engine light is on, and its idling high, its probably in failsafe mode and may have a faulty ECM (Engine Control Module) this is just a guess but it is a set of symptoms I have seen a few times on the 1996 only.

      I dont suggest running out and buying a new computer, but after some careful evaluation that may be where it takes you.

      Hope that helps, Sorry I dont have better news.


      1. Justin,

        Thanks so much. I had a thought, I read somewhere the scanner should be used with the ignition in the ‘on’ position, but without the engine running, and we had the engine running. Could this be the cause of the failed scan?

        Also, looking at a map, you are only 2hrs away (I live close to the border). If I can’t get things sorted, would it be safe enough to drive there, for your shop to take a look? As I said the vehicle seems to run fine.

        Thanks again, and have a great week!


        1. Most likely it would be ok to drive here, if the check engine light was to start flashing that would be a stop driving it kind of a thing. The scan tool should be able to read codes with the car running.


  285. Good afternoon Justin,

    I have a 1998 Outback. I am currently overseas and will be returning to the US next month. I am being told by the person driving my car while I am here that the check engine light is on and that the code is a vaccum leak. I was wondering if you know someone in the Baltimore, MD area you could recommend you look at it upon my return. Not looking for you diagnose or anything as I have read the site enough to know the CEL is about getting the fault code to start the diagnosis. Was just hoping you might know someone in my area you could recommend to start that process.

    1. Hello Scott,

      Thanks for understanding there is a limit I can offer without a code number and data. I did make a couple of phone calls, and it appears that other than the Dealer there aren’t to many options in that part of the country for you in terms of Independents.

      I would suggest maybe or Google places as places to start searching for a shop in that area.

      Hope that helps


  286. Hi Justin,
    My engine light just went on yesterday but also error message:ER HC 096043, “Sport” and “Cruise” ….. car seems to be running fine but cannot find in manual what these things mean.

    Your website seems to help many people and I hope you have some suggestions for me.

    Joan Reynolds

  287. Also, I think the day before there seemed to be water on ground….not oil and colorless so not sure related to the issues/Joan

  288. I need a little help figuring out what to do 1st. My CEL came on yesterday but when Autozone tried to use a codereader on it, there’s no power at the OBD port. I heard the fuse to your cigarette lighter could sometimes blow and would prevent power to the port also but 2 different mechanics (I was harving oil change/tires aligned) couldn’t find the fuse to check if it had blown. What do I need to do to get power to the port so I can figure out what’s causing CEL? Thanks for any help.

      1. That would be why they couldn’t find one, huh? I’m not feeling very confident that there’s anyone around here who understands Subaru’s, and seems as if there’s something unique about their insides that doesn’t correspond with every other car out there (which would be why there great cars, right?). What is likely the problem that would cause no power to the diagnostic port then, everything else in the car seems to be running fine (other than whatever the cause of the CEL coming on is). Should I be taking my car specifically to a Subaru dealership to have repairs done, or should any national chain mechanic shop (Carmax, Firestone, Midas etc.) be able to figure things out? Thanks for being there and all your help on this forum.

        1. Allison,

          I doubt there is a power problem, its most likely that the shops and parts stores near you don’t have a compatible device for your Subaru. I will tell you that anytime there is no communication to a scan tool it typically points to a faulty ECM, this is something only a Subaru guy is competent in diagnosing for you.

          The shops you mentioned have a huge disadvantage over a specialty shop, and the profit model also only allows for cheaper labor costs, cheaper labor costs do not attract the most qualified of Technicians. I started my Career at a Tire store and I have a great understanding of how they operate.

          I don’t like the Subaru dealers unless you can find a smaller market one that works a little harder for your business, I do prefer a Independent Subaru Facility for the best of both worlds.

          What do do from here is try and find a good shop that you can establish a relation ship with, if you can do this your ownership experience will also improve greatly.


  289. Hi Justin,

    I apologize for adding to this giant list of inquiries, but I am hoping you can help me out. I have not yet taken my car to a dealership as you have recommended. I have a 2001 Legacy L, and here are my symptoms:

    CEL Showing code P0328 (knock sensor, chamber 1 or something like that)

    80% of the time my car drives terribly. Slow to accelerate, feels like driving in fifth gear when it should be in first, the other 20% just reminds me how well my car could drive.

    I have replaced knock sensor, changed all fluids, use only premium gas, etc., but the issue persists. After replacing knock sensor, I left the battery unplugged overnight, and CEL stayed off for about 20 miles.

    About a week ago, my CEL turned off while driving and stayed off for a week and a tank and a half of gas.

    Tonight, I filled up at Shell and after about 20 or so miles, the CEL came back on.

    If you have any ideas, I am open to them. Thanks for reading.

    1. Hello Josh,

      The gas level and type have zero to do with the Check engine light, a P0328 could be a faulty Knock Sensor but could also be a wiring or ECM issue as well. The only way to know is to test it, meaning that a DVOM (Digital Volt Ohm Meter) Subaru Select monitor or the equivalent, a factory service publication and someone capable of performing the tests analyzing the data and determining what is wrong.

      I know you are looking for me to tell you something else, but there just isn’t anything else I can responsibly tell you to do. You don’t have to take it the Dealer, but you do need to take it to a Subaru Guy, you have already replaced the knock sensor and that was proven to be noneffective as is the case many times when merely replacing parts based on a code and no diagnoses performed. I didn’t like paying for my MRI , but as I didn’t have any choice I had to as guessing at what was wrong with my shoulder just wasn’t getting the job done. I have to point out that if you want results you are probably at the end of your capabilities.

      There are situations that I just cant help you with without seeing the car first hand and this is one of them.


  290. Hello Justin,
    So relieved to find this blog. Just bought a 2005 Outback 2.5xt today with 71k miles. I have been researching and shopping for a subaru for almost a year, and felt somewhat confident with my purchase. 3 hours later after driving the car 40 miles on the freeway home, I am freaking out, to put it mildly.
    After getting off the freeway, the engine light illuminated and the cruise light flashing. I pulled into my driveway about 4 minutes later to my awaiting family who all started talking about the “burning rubber” smell. I turned off the car, gave it a minute and restarted it. Same lights, and car seems to be idling rougher than I remember it doing so when I left the lot with it. I am so upset about this, but don’t want to overreact. The financing is not done on this deal- would it be a good idea to return the car and not finish the deal?
    Any advice would be so appreciated. I read through 2 years of posts on your blog, and you sound very knowledgeable. Just lost my dad this year who was a master mechanic and helped me with all of this:(

    1. Amy,

      The check engine light can come on for a loose gas cap and this will also cause the cruise light to flash as well (it will every time the check engine is commanded on by the Engine Control Module) I wouldn’t want to give back a good car for a loose gas cap.

      The check engine light can come on for thousands of other reasons as well, based on the information at hand its just not responsible to advise you either way, the burning smell is a concern, but what would have made the most sense was a prepurchase inspection, had that happened you would be comfortable with the car or you wouldn’t have purchased it.

      A plastic bag melted on the exhaust could be the smell, but it could also be a fluid leak which would be a concern.

      It needs to be evaluated locally, and I hate saying this but you have to have any car you are buying inspected before you buy it, or the outcome can be devastating.

      Sorry I cant offer more, and I sincerely hope it turns out ok for you.


  291. Hi Justin,
    I really appreciate the advice being given in your spare time on this page, now I must ask about my 2002 Outback that is a limited with a manual trans.

    This car has had it’s service engine light on since I bought it 15 months ago with a code of catalyst inefficiency. I had the pair of catalytic converters and the O2 sensors replaced two months ago. The CEL would come back on after driving 40, 60, 80 miles etc… every time I brought it back to the shop. Eventually they had to replace the new parts recently installed and I think they tried to get away with aftermarket stuff, but they put on OEM parts. CEL still comes back on.

    Also had a tune up as well, everything but the spark plugs were changed. They had to have the “computer” in the car reprogrammed and then it went its longest without the light, around 170 miles before it came back on. Last night the CEL started blinking, luckily I was 2 minutes form home and it only did intermittently. It definitely sounded like a misfire to me.

    The car has been in and out of the repair shop 8-9 times and this is still not solved. I trust these guys but beginning to think it might need to go to a dealership, but having $1500 sunk in already I don’t have the cash for that now. At least all these follow up visits have been free haha.

    I think there might be an underlying issue causing the catalytic inefficiency code to come up and now with the misfire, could that possibly be it? I’m really at my wits end with this and now late on getting a state inspection sticker ugh.

    Thanks for any help! Can pull codes tomorrow if needed.
    -Dave in Mass.

    1. Dave,

      First of all you need to invest in a generic code scanner so you have the code number your self each time the light comes on, so we can know if the light is coming on solely for a P0420 or if there are other issues at work.

      Its possible to set a P0420 and not have a failed catalyst which is why testing must be performed, it doesn’t sound on the surface like that has been done, no aftermarket parts will do, they don’t have enough precious metal to be a Catalyst, that’s why they are cheaper.

      Use the search feature of this website and search for the 420 code you will get an idea of the cause of the code.

      Yes you are correct that the check engine light will never blink because of a a P0420 either, only a misfire will cause a flashing check engine light and also damage a catalytic converter regardless of how new it may be.

      Ive never had 8 or 9 opportunities to correct the same code, you are patient. You need to find out what went in the car, what are the results of testing not code scans. A OE catalytic convertor coupled with a cheap generic 02 sensor will cause a check engine light and P0420 code.

      Hope that helps


  292. I have a 2006 outback with 2.5 XT turbo, I’ve had my check engine light coming on for about 2 months. I took it in for an oil change and it started to run like crap. It was kind of running rough before that but now its bad. I replaced the mass air flow sensor & reset the codes by disconnecting the battery, it did’nt fix the problem so I took it to my local subaru dealer, they played with it for 2 hours. They couldn’t find anything that was causing it to run like crap, even driving it plugged into the datascanner, nothinf. Two days later the ce came on, l went back & they said it’s misfiring on cylinder 4, so l switched ignition coils with 2 & 4 and checked it again, now 3 & 4 are misfiring. I put new coils in & the plugs are a year old, and just replaced timing belt, still runs like crap.

    Could this be a knock sensor gone bad? They said at subaru it might be bad gas, gummed up injectors, carbon build up, bad plugs loose gas cap etc. I’m running out of things to replace, kinda. I did replace O2 & fuel mixture sensors 2 months as well. Any ideas on if this could be the knock sensor?

    1. Chris,

      You have a good car with a problem that needs to be accurately diagnosed. Anytime parts are replaced without “knowing it will correct the issue” its a risk and typically an expensive one.

      You need a Subaru Expert, and they don’t work at the Dealer or if they do they weren’t assigned your car that day. Until that happens there will be no resolution.

      There is a diagnostic procedure that is to long and detailed to post. Thats what needs to be done and the solution will be found until then it will continue to be frustrating..

      A Subaru select monitor will show misfire data not just codes, then that data can be broken down further along with tests of the ignition, fuel and mechanical systems including but not limited to injector balance tests, cylinder leakage tests and valve clearance tests. All of these should be done prior to any parts replacement.

      There is a limit to what I can do minus car in front of me, I cant diagnose it from here, and you cant tow it to me, look for a me where you live. I am not the only one who understands how a car functions you just haven’t found that guy yet.


  293. Or should I just light it on fire and let it burn for insurance money. I’m tired of these problems. I bought it with thought in mind that I’m getting a high quality Japanese car, traded an Olds Aurora, but l think l should of kept it

  294. Hello,

    I have ’96 Subaru Impreza Outback, 2.2L, 122K, recently began making incredible noise and turns out the exhaust system is rusting, specifically the catalytic converter and flanges.

    I am wondering if I might be able to get away with using an after market converter or should I pay more for the Subaru part. I’m hoping to get another year at least out of the car but want expenses kept low. What are your thoughts?

    Thank you!

    1. Hi Rod,

      Thats a tough one. Because the car has so much life left I would steer you towards the Subaru Part. But I do understand the price is going to be really high on a 1996.

      There are some not as legal options such as local classifieds for part outs. But I will leave that up to you.


  295. Justin, you’re a total legend. cheers for any help you can give. I have a 2000 TX Legacy, about 175,000kms on the clock. CEL has been coming on when i hit big hills, cruising down the other side it goes off. Its just come on recently and stayed on. Otherwise the car is running fine. Any thoughts, or just the regular emmission issue?

    1. Gibbsy,

      Thanks for the kind words. Without a code number I am guessing here but I suspect a boost or boost monitoring issue since its a TX and I do believe that to be a Turbo model ( wasn’t available here in the US)

      If you can gather a code number I might be able to offer a bit more.


      1. Hey Justin
        Thanks for replying. I’m writing from the otherside of the world in New Zealand. I lose count of the number of different Subaru models we get here at about 100 so i can understand theres plenty of confusion. Its not a Turbo, TX i think was one of the most basic models of Legacy. Its 2000cc, auto, and runs great, just that cheeky little CEL bugger. I flushed the radiator and cleared out dead bugs for africa. doesnt seem to have done much. i’ll see if i can get a code from a subaru service centre.

  296. Greetings Justin,
    Thanks in advance for any advice you can provide. Your site and your free advice is admirable. I have a common problem on a unique car. Three months ago, as a gift for my 16 year old son, I purchased a 1998 Subaru Legacy GT Limited from a private party (a subaru mechanic). The mechanic had replaced the original engine with a subaru ej22 (2.2L) engine. In hindsight, I now realize I should not have bought this car for numerous reasons, but because the owner stated he was a subaru mechanic, I was not as cautious as I should have been, and I did not get the car checked. Anyway, the car has had several mechanical problems (bad caliper and leaking valve cover gaskets) which were fixed at my local subaru dealer. However, I have a continuing problem with P0303 codes (cylindar 3 misfire). Dealer says plug, wire, and ignition coil are OK. They performed some kind of $90 engine maintenance service that supposedly cleaned the injectors. The car ran for about 200 miles, then the P303 code appeared again (I have my own code reader). My question is what should I ask the dealer to do next? Is is harder to diagnose problems on this car due to the engine replacement? Thank you Justin.

      1. Thanks for reply Justin – Let’s assume for the moment that sticking valve(s) are a problem with this engine. Could sticking valves destroy the engine? Is there something that can be done to keep the problem from getting worse? For example, is there any kind of additive (to oil or fuel) that would help mitigate the sticking valves, or would I do more harm than good by fooling around with additives? Thanks for any further advice.