GMC 2007 Sierra - Manual (Page 119)

To replace the battery in the RKE transmitter, do
the following:
1. Insert a thin object, such as a coin, in the slot
between the covers of the transmitter housing
near the key ring hole. Remove the bottom
by twisting the coin.
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. See
“Resynchronization” following this information.
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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