Try this procedure if it doesn't work you will need to have the codes read with a GM scan tool .Before you do the procedure remove both battery cables and hold them together for 30 seconds and have a helper hold the brake pedal down while you are doing it.Reconnect the battery cables and perform the procedure.Hooking up a backup battery or another car running to keep your battery charged would be a good idea during the procedure since it will take 30 minutes or more.
ImportantThe vehicle learns the key transponder information and/or passwords on the ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.
With a master passkey III key, start the vehicle. The vehicle has now learned the key transponder information and the PCM has now learned the fuel continue password. With a scan tool, clear any DTCs.
Good luck,Mike.Bonuses are appreciated.