Pontiac Repair: 2004 Pontiac GP emissions, pontiac grand prix, vent valve

Question
I have a 2004 pontiac grand prix, 3800 series III V6. The emissions light is on. Tried a new gas cap worked for a while and now it is back on. Could it be a o2 sensor? Any other suggetions?

Thank you.

Answer
Hi James:

do you know what code(s) is set in the engine computer? If not it's just a guess if you don't know what the code is for your just wasting your $ buying parts that it doesn't need. did you get a DIC message of check gas cap and that is why you went in that direction? Agin this is a guess but on that make and year car the evap canister vent valve would go bad all the time and it would set wither a p0455 or a po0442 or both. Stop by any of the big box auto parts stores they usually will scan for codes for free and that way you at least know what you looking for then. Good luck :)