i was recently driving and my check engine light came one. at first i thought i had forgot to screw on my gas cap (i have done it before) but i still decided to stop at a checker. i checked my gas cap and still had one. when the worker plugged in the computer it read "fuel trim bank 1". the worker said possibly had something to do with a dirty fuel injector or the O2 sensor. when i am driving i cant tell a difference, i have noticed my gas mileage has gone down, but i am not sure if that has anything to do with it. if you have any clue about this you would be a great help!