Illumination of the Check Engine Light can be caused by a loose or worn gas cap.
Average mileage: 132,230 (112,372–189,000)
25 people reported this problem
The check engine/service engine light comes on with an issue with the EVAP system. Using a scan tool you code that comes up will either be a P0440 or P0442 code. This issue is very common with pontiac bonneville models and also the pontiac gran prix models. You can fix the issue by replacing the gas cap. This will cost anywhere from $10-$30 (this will fix this issue roughly 80% of the time) or you will have to replace eithe the EVAP canister, an EVAP solenoid, or a leak in one of the lines. This will cost about $20-$40.
When I put my gas cap on, I have to turn it past being on. I turn it until it clicks several times. Otherwise, my service engine light comes on.