Circuit/System Description

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The power door locks are controlled by the body control module (BCM) through lock and unlock printed circuit board relays in the IP fuse block. The driver and passenger door lock switches are normally open, 2 position rocker type switches, with detents for lock and unlock. The lock and unlock switch signal circuits are referenced from battery voltage by the BCM and when a door lock or unlock switch is pressed the signal circuit is closed to ground through the switch contacts and BCM determines the signal is active. The unlock relays are controlled by the BCM through driver door and passenger door low side drive control circuits and the lock relays are controlled through a single high side drive control circuit. During lock or unlock operation, battery voltage will be supplied to the lock actuators through the energized relays and grounded through the de-energized relays.