radio code ?

You may find the answers here: http://repairpal.com/gm-theftlock-radio-issues

You'll have to take it to the dealer, who will then remove the radio to get a code off of the radio. They will contact the factory and enter the code. It's part of the anti-theft system. After talking to a guy in the service department, I went by the dealers and the guy at the parts counter happened to have a sheet of codes that he had copied at no charge. He started to put the codes in one at a time. Finally, he got the radio to work. He did this at no charge to me. The guy in the service dept. wanted $45 to do the same thing.

code is on card given at time of purchase. must reinstall code after each battery change or work.

when you bought your car, they (dealership) should have given you a code to unlock your car. It also came with your owner's manual. Check that first to see if you still have the card that has the 4 digit code for the radio. If you do not have that, then talk to your dealership and they might have to replace the whole radio system and give you a new code for to unlock your radio in the future.