Driver, Passenger and Rear Lock System Operation

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. 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 lock/window switch and passenger door lock/window switch. 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 driver door lock/window switch or passenger door lock/window switch. The driver door lock/window switch or passenger door lock/window switch monitors these inputs and sends a serial data message indicating a change in the switch's respective position. Modules which activate the power door lock motors receive the serial data message and activate the motor in the appropriate direction to lock or unlock the vehicle's doors. The rear door lock switch provides a lock and unlock signal to the body control module. The body control module upon receipt of a lock or unlock signal will control the rear door lock/unlock relay and also send a serial data message to the driver door lock/window switch and passenger door lock/window switch to perform the appropriate function.

The modules which activate the power lock motors are:

The driver door lock/window switch
The passenger door lock/window switch
The body control module

The driver door lock/window switch and passenger door lock/window switch are directly connected to the respective door lock actuator through the door lock motor lock and unlock 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 body control module through the rear door lock/unlock relay which is incorporated onto the printed circuit board in the I/P fuse block. The body control module 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.