Today I performed the following maintenance on my 2007 Subaru Outback 2.5i wagon:
- Replace air filter
- Clean throttle body
- Replace PCV valve
- Replace all PCV pipes
- Replace throttle body gasket
The PCV valve in particular was in terrible condition and completely clogged of oil and the throttle body had about 1mm - 2mm of gunk build-up on the butterfly valve.
I performed all of the following and upon starting the car, the CEL was on. I immediately turned the car off and checked every electrical connector, and checked that the throttle body gasket was seated properly. All seemed fine. I then disconnected the battery and let the car sit for about 10 minutes and then I started it again. The CEL light was still on.
I let the car idle for around 15 minutes so it can get up to temp, and it seemed to be idling perfectly fine, but the CEL persisted. I decided to take it for a brief drive and it was totally fine, no odd noises, the engine was smooth and performance was good all through the rev range.
This made me think that perhaps the throttle body and PCV valve were so dirty that, after performing the maintenance, the ECU thinks theres a problem.
Is it possible that performing the above maintenance could trigger the CEL? And is it possible that the CEL is a false negative? What should I do?
EDIT: After turning the car on this morning, the CEL is gone. I guess it was a false negative! I purchased an OBD reader anyway, just in case I'm in this situation again sometime.