Passenger Door Unlock Operation - Uplevel Vehicles

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. 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 unlock position, voltage is applied to the door unlock control circuit and the BCM. When the BCM senses the voltage signal, it grounds the door unlock control circuit and the unlock relay winding. Since the other side of the unlock relay winding is connected to battery voltage, 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 UNLOCK fuse to the unlock side of the door lock actuators. Since the other side of the passengers door lock actuators are connected to the normally closed contacts of the lock relay to ground, the doors unlock.

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