Cadillac 1999 DeVille Owner's Manual page 69

1. Use the round end of the door key or a coin to pry
open the transmitter.
2. Once the transmitter is separated, use a pencil (or
similar object) to remove the old battery. Do not use
a metal object.
3. Replace the battery. Insert the new battery as the
instructions under the cover indicate.
4. Snap the transmitter back together tightly to be sure
no moisture can enter.
5. Resynchronize the transmitter.
See "Resynchronization" following.
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