A Loose or worn gas cap may cause Check Engine Light to illuminate.
Car Problem Reports
Chevrolet Silverado 1500 Check Engine Light Due to Gas Cap Issue
Chevrolet Silverado 1500 Problem
Visitor, 2009 Chevrolet Silverado 1500, 44,550 mi
i replaced the gas cap and had the computer reset....3 days later the truck told me to tighten the gas cap again. now the check engine light is back on.