GM Service Manual Online
For 1990-2009 cars only

Object Number: 807725  Size: A2

If your vehicle has this feature, you can lock or unlock all doors on your vehicle from the driver's or front passenger's door lock switch.

Press the lower portion of the switch to lock the doors. Press the upper portion of the switch to unlock the doors.

The locking lever 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.