We have encountered a few newer Model Subaru Outbacks (2010 to 2014) with a check device error message when a smart phone, tablet etc is plugged in.  This would include my 2012 Subaru Outback.

Subaru just a couple of months ago put out a TSB ( Technical Service Bulletin) to help explain this.  There is no fix mind you, just an understanding of how heat affects the low voltage systems in particular in a modern vehicle. Essentially what occurs is that in warm weather situations the increase in heat will cause a decrease in the supplied voltage to a device through the USB port the system senses the decrease in voltage and displays the error.

I have also provided the TSB information below.

Subaru Check Device Error Message

Thanks for reading

-Justin