1994 GMC Suburban Owner's Manual - Page 62

I From the inside: To lock the door, slide the lever on your door down. To unlock the door, slide the lever up. Power DoorLocks (Option) Press the bottom or the power door lock switch, marked LOCK, on either front doorto lock all the doors at once. Press the switch marked UNLOCK to unlock all the doors at once. 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. - Leaving Your Vehicle If you are leaving the vehicle, take your keys, open your door and set the locks from inside. Then get out and close the door. 2-6