Power Door Lock System Operation

WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The front power door lock switches are integral components of the driver door module (DDS) and passenger door module (PDS). The switches are 2 position normally open rocker switches. When placed in either the lock or unlock positions, the switches provide a direct input to the DDS or PDS. The DDS or PDS monitors these inputs and sends a GMLAN message indicating a change in the switch's respective position. Modules which activate the power door lock actuators receive the lock or unlock message and activate the actuator in the appropriate direction to lock or unlock the vehicle's doors.

The modules which activate the power lock motors are:

The DDS (driver door lock actuator)
The PDS (passenger front door lock actuator)
The BCM (both rear door lock actuators)

The DDS and PDS are directly connected to the respective door lock actuator through the lock and unlock control circuits. Once a door lock or unlock request has been received, the module will supply battery voltage to one side of the actuator and ground the other causing the doors to lock or unlock.

The rear passenger doors are controlled by the BCM through the rear door lock/unlock relay which is incorporated onto the printed circuit board in the LH BEC. The BCM controls the unlock relay by providing ground to energize the coil and controls the lock relay by providing battery voltage to energize the relay coil. The energized the relay and allows voltage to be applied to either the door lock motor lock or unlock circuits. Since the other side of the door lock actuator is connected to the normally closed contacts of the opposing relay to ground, the doors lock or unlock.