Porsche 911 Carrera Owner's Manual page 301

Replacing the remote-control battery
The battery should be changed when the range of
the radio remote control becomes smaller or when
the light-emitting diode no longer flashes when the
remote control is operated.
1. Using your finger nail or a small screwdriver,
carefully lift off the cover of the key grip
(arrow).
2. Replace the battery (paying attention to the
polarity). Replacement battery - Lithium CR
2032, 3 volts
3. Replace the cover and press together firmly.
Please observe the disposal instructions for
batteries.
Note
Please dispose of batteries in compliance with
any and all government regulations.
Practical Tips, Emergency Service
299