1995 GMC Yukon Owner's Manual - Page 79

There areseveral ways to lock and unlock your vehicle: From the inside: To lock the door, slide the lever onyour door down. To unlock the door, slide the lever up. Power Door Locks (Option) Press the side of the power door lock switch, marked LOCK, on either front door to lock the all doors at once. Press the ribbed sideof the switch 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. _ : 2-7