GMC 2004 Sierra - Manual (Page 106)

The following instructions tell you how to change the
automatic door unlock mode. Choose one of the
four programming options listed above before entering
the program mode. To enter the program mode, do
the following:
1. Begin with the ignition off. Then pull the turn
signal/multifunction lever toward you and hold
it there while you perform the next step.
2. Turn the key to RUN and LOCK twice. Then, with
the key in LOCK, release the turn
signal/multifunction lever. Once you do this, the
doors will lock and unlock, the horn will chirp twice,
and a 30-second timer will begin. You are now
ready to program the automatic door unlock feature.
3. Press the door unlock switch once. You will hear
one, two, three, or four chimes. The number of
chimes tells you which unlock mode is currently
selected. Continue to press the door unlock switch
until the number of chimes that you hear matches the
number of the mode that you want. If you take longer
than 30 seconds, the locks will automatically lock and
unlock and the horn will chirp twice to indicate that
you have left the program mode. If this occurs, you
can repeat the procedure beginning with Step 1 to
re-enter the programming mode.
You can exit the program mode any time by turning the
ignition to RUN. The doors will automatically lock
and unlock and the horn will chirp twice to indicate that
you are leaving the program mode. If the lock/unlock
switches are not pressed while in the programming
mode, the current automatic settings will not be
modified.
See your dealer for more information.
Rear Door Security Locks
(Crew Cab)
With this feature, you can lock the rear side doors so
that they cannot be opened from the inside by
passengers.
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