Your car uses a radio that is controlled, via data bus, by the body computer. It can also have either an amplified or non-amplified stereo system. The problem could be in the data bus circuits of either the wiring or the body computer but this would cause other problems besides just the radio. If you don't have the amplified system then you most likely have a bad radio. If you have the amplified system then it could be a bad radio OR a bad amplifier. Find a reputable car stereo shop that is knowledgable with factory systems to troubleshoot the problem for you or simply replace the radio and bypass the factory amp if equipped. There's an interface module available that will allow you to retain the door chimes and OnStar (if equipped) when replacing the factory radio with an aftermarket unit.