GM Service Manual Online
For 1990-2009 cars only

The power door lock system includes the following components:

    • The door lock actuators
    • A door lock relay
    • An door unlock relay
    • A driver door unlock relay
    • The door lock and side window switches
    • The body control module (BCM)
    • The endgate lock cylinder switch /liftgate lock cylinder switch (utility)
    • The keyless entry, if equipped

The door lock and liftgate mechanisms may be controlled by the following switches:

    • The door lock and side window switches
    • The BCM
    • The endgate lock cylinder switch / liftgate lock cylinder switch (utility)
    • The keyless entry, if equipped

The following locking functions are included on the vehicle:

    • All the doors unlock -- All the doors will unlock, including the endgate/liftgate, when any power door unlock switch is detected. The passenger doors lock directly by pressing the lock switches. The driver door unlocks by the BCM using a driver door unlock relay.
    • All the doors lock -- All the doors will lock, including the endgate/liftgate, when any power door lock switch is activated. All the lock actuators will activate directly from the power door lock switch (external to the BCM).
    • The end/lift gate lock switch -- All the doors will lock or unlock from the end/lift gate lock switch.
    • The lockout prevention -- This function will prevent the doors from automatically locking if the keys have been left in the ignition and the power door lock switch is operated.

The motor is protected by a built-in electronic circuit breaker (ECB). If the motor is overloaded or voltage is applied for an excessive amount of time, the ECB internal resistance increases, essentially creating an open circuit. The resistance returns to normal only after voltage is removed from the circuit, thereby restoring circuit continuity.