Buick 2005 Century - Manual (Page 75)

Battery Replacement
The battery in the remote keyless entry transmitter
should last about three years.
If the battery is weak the transmitter will not work within
its normal range. It is probably time to change the
battery if you have to be very close to the vehicle before
the transmitter works.
Notice: When replacing the battery, use care not
to touch any of the circuitry. Static from your
body transferred to these surfaces may damage
the transmitter.
To replace the battery do the following:
1. Insert a flat object like a thin coin into the slot on
the back of the transmitter and pry apart the front
and back.
2. Remove the old battery, but do not use a metal
object to do this. Make sure the new battery is a
type CR2032 or equivalent, and that the positive (+)
side of the battery is facing down.
3. Snap the front and back of the transmitter together.
4. Resynchronize and test the operation of the
transmitter with the vehicle.
Resynchronization
After the battery has been changed in the remote
keyless transmitter, it will need to be resynchronized.
To do this, press and hold both the LOCK and UNLOCK
buttons on the remote keyless entry transmitter until
one horn chirp is heard.
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