I am sorry that you have not been helped yet. I just came online and saw your question
you dont mention if the alarm is still going off, or if the security light is on solid on the dash or blinking, or not on at all. Also, factory or aftermarket antitheft system.
If the security light is on and not going off, do the following relearn
30 minute GM relearn procedure:
1-Turn ON the ignition, with the engine
2-Attempt to 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 10 minutes the telltale will turn OFF.
4-Turn OFF the ignition, and wait 5 seconds .
5-Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes (the vehicle is now ready to relearn the Passlock(TM) Sensor Data Code 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).
If this is not the issue, please let me know