Driver Door Unlock Operation (Uplevel 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.

The driver door unlock control circuit uses a dedicated driver door unlock relay. This is done so that the driver door may be unlocked by itself using a keyless entry unlock transmission or with an automatic door unlock function (if programmed). The driver door unlock relay differs slightly from the unlock relay in that the primary side of the relay is connected to the DR LOCK fuse and the door unlock control circuit is pulled to ground by the BCM to energize the relay.

When any of the door lock switches are placed in the unlock position, a voltage is applied to the unlock relay and to the BCM. When the BCM senses the voltage signal, it grounds the driver door unlock control circuit. Since the other side of the driver door unlock relay winding is connected to the DR LOCK fuse through the battery voltage circuit, 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 to the unlock side of the driver door lock actuator. Since the other side of the driver door lock actuator is connected to the normally closed contacts of the lock relay to ground, the driver door unlocks.

The unlock function can also be accomplished by the BCM supplying voltage to the door lock control circuit during any of the following:

A keyless entry unlock transmission
An automatic door unlock function (if programmed)