GMC 1995 Suburban Owner's Manual page 79

There are several ways to lock and unlock your vehicle:
Power Door Locks (Option)
Press the side of the
power door lock
switch, marked
LOCK, on either front
door to lock all the
doors at once. Press
the ribbed side of the
switch to unlock all
the doors at once.
From the inside: To
lock the door, slide the
lever on your door
down.
To unlock the door,
slide the lever up.
On four-door models, the switch on each rear door works only that door's
lock. It won't lock (or unlock) all of the doors
-
that's a safety feature.
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