Check Engine Light Due to Gas Cap Issue on Pontiac Sunfire

Problem Description and Possible Solution

Illumination of the Check Engine Light can be caused by a loose or worn gas cap.

Problem Data
RepairPal Verified
Average mileage: 127,355 (30,000–332,345)
10 model years affected: 1996, 1997, 1998, 1999, more2000, 2001, 2002, 2003, 2004, 2005
38 people reported this problem
Viewing 1 - 9 of 9 comments
check engine light on but says evap code
Purchased new gas cap.
got new cap
Engine light came on. Turned out the cause was the gas cap not being securely tightened. You have to hear clicks to be sure it's tight. My cap was very dirty. Cleaned it and it was fine but soon replaced it.
Engine light came on. Auto zone diagnosed vacuum leak in gas tank, basically. Replace gas cap. Week later,light back on. Recheck. Same answer. New gas cap. ( best one available). Week later same thing. Took to my mechanic. Did smoke test. Empty gas tank,fill with smoke, find hole and fix it. No hole found. Someone told me to put black tape over light! Lol. Light still on. I go to auto zone to check things every couple months to check for other possible issues, it is 15 years old now.
check engine light comes on, cause, fuel cap
check engine light on and replaced cap waiting to see the light go off hopefully soon
I can always tell when someone other than myself has messed with the gas tank lid....either its coiled up all wrong or i ge the check engine light...I then make sure during my next stop to undo the cap and retighten it, making sure it clicks at least 2-3 times. Usually, the check engine light will then go off after a couple of restars after the cap has been retightened.
My check engine light was on so i went to mechanic and it was diagnosed as it being the gas cap. replaced gas cap-problem solved! ;)