Ok, you need to do the relearn procedure
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 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).
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