Porsche 911 Carrera Owner's Manual page 186

Note
Several attempts with different distances between
the vehicle and the hand-held transmitter might be
necessary.
The fog lights will flash once the 5 minutes have
been exceeded. Programming must be repeated
from the beginning in this case.
Deleting programmed signals of the HomeLink
(e.g., when selling the vehicle)
Keep the two outer buttons 1 and 3
depressed for approx. 20 seconds until
light-emitting diode A begins to flash quick-
ly. All programmed signals of buttons 1 to 3
are deleted.
184
Controls, Instruments