A Loose or worn gas cap may cause Check Engine Light to illuminate.
Car Problem Reports
GMC Sierra 3500 HD Check Engine Light Due to Gas Cap Issue
GMC Sierra 3500 HD Problem
Exhaust & Emissions Affected: Gasoline
Visitor, 2008 GMC Sierra 3500 HD, 53,000 mi
engine light goes on. the mechanic stated that gmc has problems with the gas cap and spout