2002 GMC Savana Van Owner's Manual - Page 82

Resynchronization Resynchronization may be necessary due to the security method used by this system. The transmitter does not send the same signal twice to the receiver. The receiver will not respond to a signal if it has been sent previously. This prevents anyone from recording and playing back the signal from the transmitter. To resynchronize your transmitter, stand close to your vehicle and simultaneously press and hold the LOCK and UNLOCK buttons on the transmitter for at least five seconds. The door locks should cycle to confirm resynchronization. If the locks do not cycle, see your dealer for service. 3. Align the covers and snap them together. 4. Check the operation of the transmitter. If the transmitter does not work after battery replacement, it may need to be resynchronized to your vehicle. See "resynchronization" following. 2-11