GMC YUKON XL 2004 Owner's Manual page 101

1. Insert a dime, or similar object, in the slot between
the covers of the transmitter housing near the key
ring hole. Remove the bottom by twisting the dime.
2. Remove and replace the battery with a three-volt
CR2032 or equivalent battery, positive (+) side up.
3. Align the covers and snap them together.
4. Resynchronize the transmitter.
5. Check the operation of the transmitter.
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 that 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 press and hold the LOCK and UNLOCK
buttons on the transmitter at the same time for 15
seconds. The door locks should cycle to confirm
synchronization. If the locks do not cycle, see your
dealer for service.
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