GM Service Manual Online
For 1990-2009 cars only

Power Door Locks System Components

The power door locks system consists of the following components:

    • Body Control Module (BCM)
    • Vehicle Interface Unit (VIU)
    • Driver door lock switch
    • Front passenger door lock switch
    • Driver lock cylinder switch
    • Front passenger lock cylinder switch
    • Door lock actuators in each of the doors
    • PWR LOCK 20A fuse

Door Lock System Controls

The power door lock system is controlled by the BCM and can be activated by any one of the following:

    • A door lock switch Lock or Unlock actuation
    • A door lock cylinder switch Unlock actuation
    • A keyless entry transmitter actuation
    • An OnStar Unlock actuation using the vehicle interface unit (VIU)
    • An automatic door lock actuation, refer to Vehicle Personalization in Personalization
    • An automatic door unlock actuation, refer to Vehicle Personalization in Personalization
    • A last door closed locking (LDCL) actuation, refer to Vehicle Personalization in Personalization

Door Lock Operation

When the BCM detects a transition of either of the door lock switches to the Lock position, it switches the door lock actuator lock control circuit to voltage. Since the lock actuator unlock control circuits are at ground potential within the BCM, all the door lock actuators transition to the Lock position.

Driver Door Unlock Operation

When the BCM detects a transition of either of the door lock switches to the Unlock position, it switches the driver door lock actuator unlock control circuit to voltage. Since the door lock actuator lock control circuit is at ground potential within the BCM, the driver door lock actuator transitions to the Unlock position.

The driver door lock actuator unlock control circuit is a dedicated control circuit used only for the driver door lock actuator. This is done so that the driver door may be unlocked individually before unlocking the passenger doors using a keyless entry transmitter or an automatic door unlock function, if programmed.

Passenger Door Unlock Operation

When the BCM detects a transition of either of the door lock switches to the Unlock position, it switches the door lock actuator unlock control circuits to voltage. Since the door lock actuator lock control circuit is at ground potential within the BCM, the passenger door lock actuators transition to the Unlock position.

The door lock actuator unlock control circuits are dedicated control circuits used only for the passenger door lock actuators. This is done so that the driver door may be unlocked individually before unlocking the passenger doors using a keyless entry transmitter or an automatic door unlock function, if programmed. When this feature is active, the BCM will require a repeated unlock command to unlock the passenger doors. However, all doors will unlock when the unlock input is from a door lock switch.

Automatic Door Lock/Unlock

The automatic door lock/unlock function is a Vehicle Personalization feature with the following four programmable modes of operation:

  1. The automatic door lock feature is disabled.
  2. All of the doors lock when the vehicle is shifted out of Park with the ignition ON.
  3. All of the doors lock when the vehicle is shifted out of Park with the ignition ON, and all of the doors unlock when the ignition is turned OFF.
  4. All of the doors lock when the vehicle is shifted out of Park with the ignition ON, and all of the doors unlock when the vehicle is shifted into Park.

The automatic door lock function can only be enabled by the BCM if the driver door switch is in the Inactive state, meaning the door is closed. For information on programming the automatic door locks, refer to Vehicle Personalization in Personalization.

Lockout Prevention

This function is intended to prevent the vehicle operator from locking the doors if the key is left in the ignition and the driver door is open. The lockout prevention function can be overridden by the BCM if the BCM receives a door Lock input for longer than 3 seconds.

Last Door Closed Locking (LDCL)

The LDCL function is a Vehicle Personalization feature that is intended to allow the doors to be locked while passengers are exiting the vehicle. When LDCL is in Active Mode, the BCM will delay locking of the vehicle doors for 5 seconds after all of the doors have been closed. The LDCL function will be overridden if the BCM receives a door Unlock input or a key in ignition input.

Key Cylinder Unlock

The BCM will unlock all of the doors after detecting a door lock cylinder switch in the Unlock position for greater than 1 second.