Your Subaru Check Engine Light Explained
November 8th, 2007 by Justin Stobb | 109 responses
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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
The Author: Justin Stobb
About: All Wheel Drive Auto is a unique independent Subaru service & repair facility. We combine years of dealer experience with a local neighborhood shop atmosphere. We use Subaru parts & test Equipment and have the expert knowledge to fix it right the first time.
This entry was posted by Justin Stobb, on Thursday, November 8th, 2007 at 5:29 am and is filed under All Wheel Drive Auto News, Blogroll, Subaru Maintenance, Subaru Repair Seattle. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response on the right, or trackback from your own site.
June 25th, 2008 at 8:31 pm
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.
June 26th, 2008 at 12:34 am
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
October 8th, 2008 at 4:44 pm
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.
October 10th, 2008 at 4:43 am
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.
Justin
November 23rd, 2008 at 9:58 pm
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.
November 23rd, 2008 at 10:41 pm
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.
November 24th, 2008 at 3:33 am
Glad we could help in some way
December 16th, 2008 at 8:33 am
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
December 29th, 2008 at 9:06 pm
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?
January 15th, 2009 at 4:41 am
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?
January 15th, 2009 at 6:51 am
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.
Justin
January 22nd, 2009 at 6:28 am
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.
Francois
January 24th, 2009 at 6:48 pm
You want to connect the scanner to the OBDII connector on the drivers side under dash area.
A scan is only the beginning mind you.
February 22nd, 2009 at 6:22 am
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.
February 22nd, 2009 at 7:20 am
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.
Justin
February 22nd, 2009 at 11:36 pm
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.
February 27th, 2009 at 7:10 pm
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!
March 21st, 2009 at 3:28 am
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?
March 21st, 2009 at 3:40 pm
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.
Justin
March 21st, 2009 at 10:44 pm
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.
April 6th, 2009 at 10:35 pm
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!
April 10th, 2009 at 11:00 pm
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.
April 13th, 2009 at 9:42 pm
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.
April 15th, 2009 at 12:41 am
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!
Jan
April 17th, 2009 at 9:24 pm
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.
April 27th, 2009 at 3:57 pm
97 postal legacy.. does speed sensor 2 input to ECM and if not working could it produce rough running and stalls?
May 2nd, 2009 at 6:32 pm
T Robert,
Speed sensors do not typically cause a rough running issue on a Subaru.
Justin
May 11th, 2009 at 3:56 pm
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:)
May 12th, 2009 at 5:37 pm
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.
Justin
May 13th, 2009 at 1:56 pm
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.
Kent
May 26th, 2009 at 5:25 pm
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.
Justin
June 12th, 2009 at 4:38 am
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?
June 13th, 2009 at 5:05 pm
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.
June 16th, 2009 at 4:48 am
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!
June 16th, 2009 at 12:39 pm
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.
June 16th, 2009 at 12:42 pm
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.
June 16th, 2009 at 10:27 pm
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.
Justin
June 20th, 2009 at 4:22 am
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?
June 23rd, 2009 at 4:03 pm
Allen,
There is just no knowing without at least the code information. Most likely a P0420 Catalyst code if I had to guess.
Justin
June 24th, 2009 at 3:37 am
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
June 24th, 2009 at 5:49 pm
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
June 30th, 2009 at 5:42 pm
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!
–
max
July 1st, 2009 at 10:49 pm
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.
Justin
July 2nd, 2009 at 4:15 pm
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.
July 2nd, 2009 at 4:16 pm
Forgot to say it’s a 2004 Forrester.
July 2nd, 2009 at 4:39 pm
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.
Justin
July 7th, 2009 at 2:35 am
Thanks. I made it home alright but the light has yet to go off. Not sure what to do next?
July 7th, 2009 at 5:21 pm
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,
regards,
Steve
July 8th, 2009 at 2:45 am
David,
If the light is still on you really want to at least have it looked at, and decide from there how important it is to fix it.
Justin
July 8th, 2009 at 2:57 am
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.
Justin
July 19th, 2009 at 2:54 am
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.
Lisa
July 20th, 2009 at 4:22 pm
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.
Justin
July 21st, 2009 at 3:42 pm
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.
John
July 23rd, 2009 at 1:47 am
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?
Thanks
July 23rd, 2009 at 3:40 pm
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.
Justin
July 23rd, 2009 at 3:49 pm
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.
Justin
July 24th, 2009 at 3:31 pm
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!
Kathleen
August 1st, 2009 at 4:22 pm
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.
pete
August 3rd, 2009 at 12:59 am
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.
August 6th, 2009 at 3:02 pm
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.
Justin
August 17th, 2009 at 6:40 pm
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.
August 19th, 2009 at 12:59 pm
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.
August 21st, 2009 at 7:50 am
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
Thanks
August 21st, 2009 at 11:06 pm
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?
August 24th, 2009 at 7:59 pm
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.
August 24th, 2009 at 10:54 pm
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.
Justin
August 24th, 2009 at 11:26 pm
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.
Justin
August 24th, 2009 at 11:43 pm
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.
Justin
August 28th, 2009 at 10:13 pm
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
August 30th, 2009 at 12:25 am
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,
Melissa
August 30th, 2009 at 1:33 am
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?
August 30th, 2009 at 3:16 am
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?
August 31st, 2009 at 12:34 am
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?
August 31st, 2009 at 7:55 pm
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?
Justin
August 31st, 2009 at 7:57 pm
Sheila,
The 02 heater circuit should be diagnosed and repaired, sometimes a shorted 02 sensor can cause damage to the vehicles computer if let go.
Justin
September 1st, 2009 at 9:18 pm
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.
September 8th, 2009 at 3:07 pm
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?
September 8th, 2009 at 3:51 pm
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.
Justin
September 9th, 2009 at 3:31 pm
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
September 14th, 2009 at 5:00 pm
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.
September 15th, 2009 at 11:42 pm
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!
Jim
September 21st, 2009 at 1:46 am
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?
September 21st, 2009 at 4:06 pm
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
Justin.
September 22nd, 2009 at 5:03 pm
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?
Thanks,
Pat
September 25th, 2009 at 1:30 am
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.
John
October 4th, 2009 at 9:02 pm
i have a 2002 subaru forester that has a check engine light on that is flashing why is it flashing and not constant
October 28th, 2009 at 7:58 pm
If your CEL is flashing, you need to see a mechanic pronto
November 23rd, 2009 at 3:45 pm
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
November 30th, 2009 at 7:24 pm
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??
December 2nd, 2009 at 5:59 am
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.
Justin
December 2nd, 2009 at 6:04 am
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.
Justin
December 14th, 2009 at 4:40 am
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.
December 16th, 2009 at 2:17 am
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?
December 30th, 2009 at 5:16 pm
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.
January 6th, 2010 at 3:21 pm
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!
Beth
January 7th, 2010 at 8:01 pm
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?
January 11th, 2010 at 9:31 pm
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.
January 18th, 2010 at 6:33 pm
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.
January 24th, 2010 at 3:06 pm
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.
January 26th, 2010 at 6:32 pm
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
January 29th, 2010 at 6:31 pm
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.
February 3rd, 2010 at 9:20 pm
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.
February 26th, 2010 at 5:53 pm
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!
March 3rd, 2010 at 4:32 pm
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?
March 6th, 2010 at 4:46 pm
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.
Justin
March 7th, 2010 at 3:18 pm
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…
March 9th, 2010 at 7:28 pm
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 ?
March 11th, 2010 at 3:43 am
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
Justin
March 11th, 2010 at 3:50 am
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.
Justin