You might want to check with Chevrolet's Customer Service center to see if there is a recall on the vehicle for this problem. You might be able to get it repaired at no cost. If you have already done this and the dealer is not able to fix it, try going to a different Chevrolet dealer.
If you still can't get the problem fixed, call 800-222-1020. It's Chevrolet's customer service number.