I replaced the cap with a new one and light did not go off.
It's had the check engine light since
Gas cap was too loose. Tightened it up, problem solved.
Check engine light stayed on for a few days, and my wife took vehicle to chevrolet dealer for service. The mechanic said there was a leak around the gas cap area and they fixed. I was charge for 1 hour labor plus tax.
Used diagnostic code reader, and it gave me the problem "evaporative system leak". Auto parts store said change the gas cap. Got new cap, problem solved
Loose gas cap = "check engine" light. reset/replaced cap, no problem since.