Illumination of the Check Engine Light can be caused by a loose or worn gas cap.
Car Problem Reports
Buick Century Check Engine Light Due to Gas Cap Issue
Buick Century Problem
Model Year Affected: 2005
Average Mileage: 105,500 mi (88,000 mi - 123,000 mi)
Visitor, 2005 Buick Century, 123,000 mi
check engine light came on. Mechanic checked code, cleared it and suggested we tighten gas cap to at least three "clicks". Three months later problem has not returned
Visitor, 2005 Buick Century, 88,000 mi
check engine light came on and stayed on code said vacume leak I replaced gas cap with new one and cleared code and light never came on again.