My trucks check engine light was on and they say it is the fuel cap not being tight enough. What other emission problems could there be if this is not the problem like they say?

Bad fuel cap--the O-ring seal could have deteriorated.

Bad fuel cap--the O-ring seal could have deteriorated.

I went and bought a new cap but it still comes on and stays on and won't go off. The dealership said that was the problem too. What else do you think it could be? Thanks for the help.

Did you try erasing the code, using a code reader or scan tool? The light may go out on its own, after driving the car for a day or two.

I thought if you disconneced the battery it would cancel the code so I did that and it didn't?