Okay, when I first bought this 2003 Sunfire Coupe (bought it new) I went out and spent money buying a locking gas cap. No problems until last week when the "Check Engine" light came on. I brought it into the dealership and was told that I could NOT use a locking gas cap. They charged me $50 for my ordeal. What an expensive lesson. If it's true that we can't use locking gas caps why ioan the hell doesn't the manual say this???

where did you get the cap from?? Check with the parts department and see if they carry one. If it's a GM cap, not much they can say. Did they test the cap or just pull a code?

I have a locking cap on my 2002 cav... I got it at autozone and I havent had any problems?