All Door Unlock
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
The multifunction alarm module unlocks all of the doors when you press UNLOCK once on either the door lock switch or on the keyless remote.
Pressing UNLOCK once on either door lock switch connects ground to the multifunction alarm module. When the circuit is grounded it cycles the door lock actuator control circuit from a normally grounded circuit to battery positive voltage. This supplies power to the door lock actuators and receives ground from the multifunction alarm module.