GM Service Manual Online
For 1990-2009 cars only
    • Resynchronization may be necessary due to the security method used by the remote keyless entry system.
        The transmitter does not send the same signal twice to the body control module (BCM).
    • The BCM will not respond to a signal that has been sent previously.
        This prevents anyone from recording and playing back the signal from the transmitter.
    • The panic button should still operate normally when the system is out of synchronization.
    • Resynchronization may be necessary under the following conditions:
       - The battery in the transmitter is very weak.
       - The battery in the transmitter was replaced.
       - The battery in the vehicle has been in a low or no charge condition for an extended period of time.
    • In order to resynchronize the transmitter with the BCM, perform the following steps:
        1. Stand within 1.5 meters (5 ft) from the vehicle.
        2. Simultaneously press and hold the LOCK and UNLOCK buttons on the transmitter for 7 seconds.

The door locks should cycle and the park lamps should flash in order to confirm resynchronization.