2004 Pontiac Grand Prix Q&A
2004 Pontiac Grand Prix Question: check engine light is on. I get a message to check gas cap.
If the lamp has not gone out after a few days you will need to have a service shop or dealer run a diagnostic test on the fuel evaporative system. The onboard fuel emmisions system test itself for possible evaporative leaks in the fuel tank and lines. It has turned the light on because a sensor indicates the system will not hold pressure. This is not a safety issue...and emmisions issue. - milesauto
Illumination of the Check Engine Light can be caused by a loose or worn gas cap.
I've owned this car for 4 years now and since I bought it I've replaced the gas cap 5 times trying to get the "check gas cap" notice to go away. As well as the check engine light. I had the car's c...