A Loose or worn gas cap may cause Check Engine Light to illuminate.Google+
Car Problem Reports
Pontiac Torrent Check Engine Light Due to Gas Cap Issue
Pontiac Torrent Problem
Average Mileage: 84,000 mi (50,000 mi - 118,000 mi)
Visitor, 2006 Pontiac Torrent, 118,000 mi
My check engine light comes on every gas tank fuel fill at different levels. I changed my cap and it is still doing it
Visitor, 2006 Pontiac Torrent, 50,000 mi
The gas cap wore out, and I replaced it for about $20.
Visitor, 2006 Pontiac Torrent
My Check Engine Light was going on, too, even though I'd securely tighten the gas cap after fueling. Even after I had the gas cap replaced, it'd occasionally go on. I just live with it.