Try this procedure exactly as its' stated and if the car starts great but if not suspect the ignition lock cylinder (includes the theft sensor) is defective.
10 Minute Learn Procedure
Turn ON the ignition, with the engine
Attempt to start the engine, then release the key to ON, vehicle will not start.
Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.
Turn OFF the ignition, and wait 5 seconds.
The vehicle is now ready to relearn the Passlock™ Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK.
Important: The vehicle learns the Passlock™ Sensor Data Code and/or password XXXXX the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.
Start the engine, the vehicle has now learned the Passlock™ Sensor Data Code and/or password.
With a scan tool, clear any DTCs if needed, history DTCs will self clear after 100 ignition cycles.