A Loose or worn gas cap may cause Check Engine Light to illuminate.Google+
Car Problem Reports
Chevrolet Silverado 1500 Check Engine Light Due to Gas Cap Issue
Chevrolet Silverado 1500 Problem
Average Mileage: 70,760 mi (44,550 mi - 104,000 mi)
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.
Visitor, 2010 Chevrolet Silverado 1500, 87,000 mi
Diagnostic code comes up to say emissions leak and was told preferably to change gas cap, but when I did replace the cap, I unhooked the battery thinking it would reset and if the problem had been resolved then the check engine light would not come back on. Not the case, however, because the light came back on and I am again looking for a resolution.
Visitor, 2008 Chevrolet Silverado 1500, 104,000 mi
Engine light comes on- attributed to a sensor for emission control
Replaced it but it returned less than a week later