Chevrolet 2001 Impala Owner's Manual page 82

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.
2-12
To replace the battery do the following:
1. Insert a flat object like a coin into the slot on the
back of the transmitter. Gently pry apart the front
and back.
2. Gently pry the battery out of the transmitter. Do not
use a metal object.
3. Put the new battery into the transmitter as shown
on the transmitter (use type CR2032 battery
or equivalent).
4. Put the two halves back together. Make sure the
halves are together tightly so water won't get in.
5. Resynchronize and then test the transmitter.
Resynchronization
After you have changed the battery in your transmitter,
you will need to resynchronize the transmitter.
To do this, press the LOCK and UNLOCK buttons
on the transmitter together and hold for approximately
seven seconds or until one brief horn chirp is heard.