A Loose or worn gas cap may cause Check Engine Light to illuminate.Google+
Car Problem Reports
Buick Rainier Check Engine Light Due to Gas Cap Issue
Buick Rainier Problem
Average Mileage: 82,528 mi (38,000 mi - 120,000 mi)
Visitor, 2005 Buick Rainier, 120,000 mi
Bought a new gas cap
Visitor, 2004 Buick Rainier, 38,000 mi
removed gas cap and reinstalled. After a tank of gas the light went off. It has occurred twice with same result.
Visitor, 2004 Buick Rainier, 85,000 mi
A Toy Story Sticker solved this one for me. I stuck it right over the indicator light!! THe darn thing comes on EVERY time that I am almost empty. As soon as I fill up, it may go off, it may not. Sometimes I only have to turn the car off, go outside and screw the cap on again. It's not a very smart car.
Visitor, 2004 Buick Rainier, 95,000 mi
Check engine light comes on frequently due to gas cap :(
Visitor, 2004 Buick Rainier, 88,700 mi
Gas cap no longer latches causing the check engine light to illuminate.