Driver and Passenger Door Lock Operation (Base Vehicles)
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
When any of the door lock switches are placed in the lock position, voltage is applied to the door lock control circuit and the lock relay winding. Since the other side of the lock relay winding is connected to ground, the relay is energized. This causes the contacts to close and complete the path from the DR LOCK fuse through the battery voltage circuit. Voltage is then applied through the LOCK fuse to the lock side of the door lock actuators. Since the other side of the all the door lock actuators are connected to the normally closed contacts of the unlock relay to ground, the doors lock.
The lock function can also be accomplished by the BCM supplying voltage to the door lock control circuit during a delay lock function (utilities only).