A Loose or worn gas cap may cause Check Engine Light to illuminate.Google+
Car Problem Reports
Chevrolet Cobalt SS Check Engine Light Due to Gas Cap Issue
Chevrolet Cobalt SS Problem
Visitor, 2006 Chevrolet Cobalt SS, 85,000 mi
Well I've tried everything to get rid of the engine light warning. With no luck, good news is the car still runs like a champ with 130,000 miles on it.