2005 Pontiac Bonneville Q&A
2005 Pontiac Bonneville Question: The check engine light comes on, it might be the fuel cap not sealing tight.
You can try cleaning off the rust and replacing the cap. But be very careful not to allow any debris to fall into tank when cleaning the rust. - Chevy Power
could be several issues but if there is a seal issue with cap that needs to addressed 1st - globalhelper