GM Service Manual Online
For 1990-2009 cars only

Door Lock System Components

The power door lock system consists of the following components:

    • Driver door lock switch
    • Front Passenger door lock switch
    • Door Lock/Unlock Relay
    • PWR ACC Fuse 15A
    • Body Control Module (BCM) -- on vehicles with keyless entry

Door Lock System Controls

The power door lock system can be controlled by any of the following:

    • A power door lock switch activation
    • A keyless entry command, on equipped vehicles

All Door Lock and Unlock-w/o Keyless Entry Option Operation

Pressing LOCK on either door lock switch applies battery positive voltage to all the door lock actuator lock control circuits. All the door lock actuator unlock control circuits are grounded through the unlock portion of both door lock switches, energizing all of the door lock actuators, locking all of the doors.

Pressing UNLOCK on either door lock switch applies battery positive voltage to all the door lock actuator unlock control circuits. All the door lock actuator lock control circuits are grounded through the lock portion of both door lock switches, energizing all of the door lock actuators, locking all of the doors.

Driver and Passenger Door Lock and Unlock-w/ Keyless Entry Option Operation

Pressing LOCK on either door lock switch sends a signal to energize the door lock relay portion of the door lock/unlock relay and also sends a signal to the BCM. When the door lock relay portion of the door lock/unlock relay is energized, the door lock actuator lock control circuits are switched to battery positive voltage. The passenger door lock actuator unlock control circuits are grounded through the door unlock relay portion of the door lock/unlock relay and the driver door lock actuator unlock control circuit is grounded through the BCM, completing the path to ground, energizing all of the door lock actuators, locking all the doors.

The lock function can also be accomplished by the BCM having received a keyless entry door lock command.

Pressing UNLOCK on either door lock switch sends a signal to energize the door unlock relay portion of the door lock/unlock relay and also sends a signal to the BCM. When the door unlock relay portion of the door lock/unlock relay is energized, the door lock actuator unlock control circuits are switched to battery positive voltage and the BCM switches the driver door lock actuator unlock control circuit to battery positive voltage. The door lock actuator lock control circuits are grounded through the door lock relay portion of the door lock/unlock relay, completing the path to ground, energizing all of the door lock actuators, unlocking all the doors.

The unlock function can also be accomplished by the BCM having received a keyless entry door unlock command. Keyless entry personalization allows the driver door to be unlocked individually before unlocking the passenger doors. When this feature is active, the BCM will require a repeated unlock command to unlock the passenger doors.

Lockout Prevention

The BCM does not allow the driver door to stay locked when you press LOCK on either door lock switch with the lockout prevention feature active. The BCM activates the lock out prevention feature when the following conditions exist:

    • A vehicle door is open
        An open vehicle door sends a ground signal to the BCM door ajar switch input
    • The key is fully inserted in the ignition cylinder
        Full insertion of the key sends a ground signal to the BCM key in ignition input

Lockout Prevention Override

The BCM overrides the lockout prevention and locks all of the doors. This feature occurs when you press the lock switch on the key fob.

Unlock After Air Bag Deployment

This feature will unlock all of the vehicle doors 15 seconds after air bag deployment.