This could be bad faith on dealer's part. The first thing you may want to do is contact GM. If they too refuse to help, get in touch with a consumer protection attorney.
Find someone good here:
lemon law applies to new vehicles. If the dealership has rejected any requests for repair or replacement made in writing, then it may be time to contact a consumer law attorney. Take all the paperwork with you. You can also call the consumer office at the Dept. of Justice.
DISCLAIMER: I am not your attorney and readers employ any information provided herein at their own risk. Any comment is for general educational purposes only, and is based only on the limited facts provided, which may or may not be true. It is not legal advice upon which you may rely, as the commenter has not interviewed witnesses or examined any evidence, and has not researched the applicable law. Available defenses may prevent the success of any claim. Competent legal advice should always be obtained from a lawyer licensed in your jurisdiction before taking any legal action or filing suit.