GMC 2003 C4C042 Owner's Manual page 86

2. Remove and replace the battery, positive (+) side
down. Use one Panasonic
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.
R
type CR2032 battery:
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 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.
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