GM Service Manual Online
For 1990-2009 cars only

Important: Synchronization may be necessary under the following conditions

   • If the immobilzer programming procedure has been performed.
   • If the transmitter is activated more than 255 times while the transmitter is out of range of the intelligent switching unit's antenna
   • Synchronization may be necessary due to the security method used by the remove keyless entry system. The transmitter does not send the same signal twice to the intelligent switching unit (ISU).
   • The ISU will not resond to a signal that has been sent previously. This prevents anyone from recording and playing back the signal from the transmitter.
   • The battery in the transmitter was replaced.
   • The battery in the vehicle has been in a low or no charge condition for an extreme period of time.

Transmitter Synchronization Procedure

In order to resynchronize the transmitter with the ISU, perform the following steps:

    • Stand within 1.5 m (5 ft) from the vehicle.
    • Simultaneously press and hold the LOCK /UNLOCK and TRUNK buttons on the transmitter for 10 seconds. The LED on the transmitter will flash fast and then stop flashing
    •  Comfirm proper operation by pressing the LOCK/UNLOCK button.