You can check the fuses first under the hood and inside, but expect to make an expensive trip to the dealer. GM has cleverly designed in a number of tricks to cost unsuspecting owners money after the sale. Simply disconnecting the battery or letting it run dead leads to computers locking up. They must be unlocked or reprogrammed by the dealer. There is no valid reason to do that except to keep you coming back. Only Volkswagen and BMW have more customer-unfriendly business practices.