I have a 2003 Civic. The other day the malfunction indicator light came on.

The manual states that this could be caused by a loose gas cap, and that tightening the gas cap will fix the problem. It also states that the light will not go off until you make one trip with the car. I checked the cap, and sure enough, it was loose. I tightened the cap, and then made one trip. Now, when I turn on the car, the malfunction indicator light still comes on.

I'm convinced that this has something to do with the gas cap. I've never found it loose like that before. I'm lost, though, as to why tightening the gas cap did not fix the problem. Am I missing something?

 

Reset the ECU, see if the CEL comes back on. or check to code it is giving you.