I am sorry that you have not been helped yet. I just came online and saw your question
Ok, the first step is to do the 30 minute relearn procedure. The battery does need to be strong for this.
30minute GM relearn procedure:
1-TurnON the ignition,with the engine OFF.
2-Attemptto start the engine,then release the key to ON (vehicle will not start).
3-Observe the SECURITY telltale(this is the security light), after approximately 10minutes the telltale will turn OFF.
4-Turn OFF the ignition, and wait 5 seconds .
5-Repeat steps 1through 4 two more times for a total of 3 cycles/30 minutes(the vehicle is now ready to relearn the Passlock(TM) Sensor DataCode and/or passwords on the next ignition switch transition from OFF to CRANK). IMPORTANT: The vehicle learns the Passlock(TM)Sensor Data Code and/or password ***** the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.
6-Start the engine(the vehicle has now learned the Passlock(TM) Sensor Data Code and/or password).