Just ran my buddies scan tool and it says that bank 1 is lean. What should I do? Also just to let you guys know I was driving home from Auburn, Alabama and I popped the hood after my check engine light came on and I noticed that the fine people at Carl Gregory Ford in Auburn had for gotten to replace my oil filler cap when they changed my oil. Could this have something to do with the engine light?
Thanks,
Simon

 

Yes that will cause it, unmetered air is being pulled into the oil filter neck causing the ECU to over correct the injectors throwing the fuel trims out.

Put a new cap on it then clear the code all should be fine.

Bob

 

whitebolt01, Bob is on the money with his anwser. Same reason a chip is needed when adding the breather mod.

 

cool thanks guys. just amking sure its nothing major. like a new motor

 

bump

 

I had the same problem and it turned out being the bottom of the intake boot was folded under when I put it back on after cleaning the throttle body.