GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 Century 🢒 Body and Accessories 🢒 Body Control System 🢒 Power Door Locks Circuit Description

Automatic Door Lock Features

The BCM has the following automatic door lock features:

All door unlock: The BCM unlocks all of the doors when you press UNLOCK on either door lock switch.

All door lock: The BCM locks all of the doors when you press LOCK on either door lock switch.

Last door closed locking: The BCM locks all of the doors 5 seconds after the vehicle doors are closed. This feature occurs if the ignition switch is in the LOCK position and the key is removed from the ignition and you press LOCK on either door lock switch.

Lockout prevention: The BCM does not lock the doors is you press LOCK on either door lock switch if the key is in the ignition cylinder and the driver door is open.

Lockout prevention override: The BCM overrides the lockout prevention and locks all of the doors. This feature occurs when you press and hold LOCK on either door lock switch for at least three seconds.

Shift into PARK unlock: The BCM unlocks all of the vehicle doors when the transaxle is shifted into PARK.

Shift out of PARK lock: The BCM locks all of the vehicle doors when you shift the transaxle out of PARK and the driver door is closed.

Automatic door lock relock: The BCM locks the doors when all of the doors are closed, the ignition switch is in RUN and the transaxle is out of PARK.

Remote driver door unlock: The BCM locks the driver door when you press UNLOCK on the keyless entry transmitter.

Remote all door unlock: The BCM unlocks all of the vehicle doors when you press UNLOCK on the keyless entry transmitter again within 5 seconds of pressing unlock.

Remote all door lock: The BCM locks all of the vehicle doors when you press LOCK on the keyless entry transmitter.

Refer to Keyless Entry System Description in Keyless Entry for more information about the keyless entry system.

Refer to Body Control System Operation in Body Control System for more information about the BCM.

All Door Unlock

The BCM unlocks all of the doors when you press UNLOCK once on either door lock switch.

Pressing UNLOCK once on either door lock switch sends a ground signal to the BCM through CKT 781. The ground signal causes the BCM to supply voltage from CKT 1540 to CKT 294 for 315-385 ms. The voltage energizes all of the passenger door actuators and unlocks all of the passenger doors. At the same time, the BCM grounds CKT 1391 and energizes the door lock relay. The energized door lock relay supplies voltage in CKT 694. The voltage energizes the driver door lock actuator and unlocks the driver door lock.

All Door Lock

The BCM locks all of the doors when the following actions occur:

    • You press LOCK once on either door lock switch.
    • All of the doors are closed.

The BCM delays door locking when the following conditions exist:

    • The key is removed from the ignition switch.
    • The driver door is open.

The delay enables the last door locking feature. The last door locking feature is enabled the first time that you press LOCK on a door lock switch. The BCM sounds the chime 3 times in order to indicate that the last door closed locking feature is active. The BCM locks all of the doors 5 seconds after all of the doors are closed. You can bypass the last door closed locking feature by pressing LOCK on a door lock switch 2 times. The BCM locks all of the doors immediately with a door still open.

The BCM does not lock the doors when the following conditions exist:

    • The driver door is open.
    • The key is fully inserted in the ignition switch.

The above conditions enable the lockout prevention feature.

Pressing LOCK on either door lock switch sends a ground signal to the BCM through CKT 780. The last door closed locking feature and the lockout prevention feature indicate to the BCM when it is appropriate to lock the doors. When it is appropriate to lock the doors, the BCM applies voltage from CKT 1540 to CKT 295 for 315-385 ms. This action energizes all of the door actuators and locks all of the vehicle doors.

Last Door Closed Locking

The BCM activates the last door locking feature when the following conditions exist:

    • The last door locking mode is enabled. Refer to Feature Customization later in this section for more information.
    • A vehicle door is open.
        An open vehicle door causes an open signal in CKT 49 and CKT 727.
    • The key is removed from the ignition switch. This action disables lockout prevention.
        When the key is removed from the ignition switch, there is an open signal in CKT 80.
    • You press LOCK once on a door lock switch or keyless entry transmitter.

When you press LOCK, the BCM sounds the chime 3 times. The chime indicates that the last door locking feature is active. The BCM locks all of the doors 4.5-5.5 seconds after all of the doors are closed.

Complete the following steps in order to cancel the last door closed locking feature:

  1. Press UNLOCK on a door switch or on a keyless entry transmitter.
  2. Turn the ignition switch to the ACC or the RUN position.

Press LOCK twice in order to override the last door closed locking feature. The BCM locks all of the doors immediately with a door still open.

Lockout Prevention

The BCM does not lock the vehicle doors when you press LOCK on either door lock switch with the lockout prevention feature active. The BCM activates the lockout prevention feature when the following conditions exist:

    • A vehicle door is open.
        An open vehicle door causes a ground signal in CKT 49 or CKT 727.
    • The key is fully inserted in the ignition switch cylinder.
        Full insertion of the key causes a ground signal in CKT 80.

The BCM disables the following automatic door lock features:

    • All door lock
    • Last door closed locking
    • Keyless entry system unlock

Lockout Prevention Override

Press and hold LOCK on either door lock switch for 3 seconds in order to override the lockout prevention feature. Holding LOCK for 3 seconds causes the BCM to lock all of the doors immediately.

Shift Into PARK Unlock

The BCM unlocks all of the doors when the following conditions exist:

    • The automatic door lock/unlock is in mode 3. Refer to Feature Customization later in this section for details.
    • The ignition switch is in the RUN position.
    • A transaxle range PRNDL signal is transmitted to the transaxle via the Class II serial data link. The transaxle is shifted into PARK.

Shift Out Of Park Lock

The BCM locks the doors when the following condition exist:

    • The automatic door lock/unlock feature is in one of the following modes:
       - Mode 2
       - Mode 3
       - Mode 4
    • All of the vehicle doors are closed.
        Closed vehicle doors cause an open signal in CKT 49 and CKT 727.
    • The ignition switch is in the RUN position.
    • A transaxle range PRNDL signal is sent to the transaxle via the Class II serial data link. The transaxle is shifted out of PARK or NEUTRAL.

Automatic Door Lock Relock

The BCM locks all of the doors when the following conditions exist:

    • Automatic door lock/unlock is in one of the following modes:
      • Mode 2
      • Mode 3
      • Mode 4
    • All of the vehicle doors are closed.
        Closed vehicle doors cause an open signal in CKT 49 and CKT 727.
    • The ignition switch is in the RUN position.
    • A transaxle range switch PRNDL signal is transmitted to the transaxle via the Class II serial data link.
    • You press UNLOCK on either door lock switch.
    • A vehicle door is open.
        An open door causes a ground signal in CKT 49 or CKT 727.
    • All of the vehicle doors are closed.
        Open vehicle doors cause an open signal in CKT 49 and CKT 727.

Feature Customization

Automatic Door Lock/Unlock Modes

There are four automatic door lock/unlock modes:

    • Mode 1
        The automatic door lock/unlock feature is disabled.
    • Mode 2
       - All of the doors lock when you shift the transaxle out of PARK.
       - There is no automatic door lock.
       - The automatic door lock relock feature is active.
    • Mode 3
       - All of the doors lock when you shift the transaxle out of PARK.
       - All of the doors unlock when you shift the transaxle out of PARK.
       - The automatic door lock relock feature is active.
    • Mode 4
       - All of the doors lock when you shift the transaxle out of PARK.
       - The driver door unlocks when you shift the transaxle into PARK.
       - The automatic door lock relock feature is active.

Changing the Automatic Door Lock/Unlock Mode

There are two ways to change the automatic door lock/unlock mode:

    • The Tech 2 scan tool method
        Complete the following steps in order to change the automatic door lock/unlock mode using the Tech 2 scan tool method:
    • At the SELECT SYSTEM screen select BODY.
    • Then select the car line and nameplate.
    • At the APPLICATION MENU screen select PERSONALIZATION.
    • At the next APPLICATION MENU screen select SET OPTIONS.
    • At the next APPLICATION MENU screen select the mode you want.
    • The door lock switch method.

Complete the following steps in order to change the automatic door lock/unlock mode using the door lock switch method:

  1. Close all of the vehicle doors.
  2. Turn the ignition switch to the RUN position.
  3. Firmly depress and hold the brake pedal.
  4. Press and hold LOCK on either door lock switch.
  5. Hold LOCK on the door lock switch and complete the following steps:
    6. • Shift the transaxle out of PARK.
    • Shift the transaxle back into PARK.
  6. Complete the following steps in order to advance the mode:
    7. • Shift the transaxle out of PARK.
    • Shift the transaxle back into PARK.
  7. The BCM sounds the chime a number of times equal to the automatic door lock/unlock mode. A transition past mode 4 repeats the sequence starting with mode 1.

    8. Release the door lock when you obtain the desired mode. Releasing the door lock will exit and save the current customization mode.

Mode 3 is set when the vehicle is manufactured. Disconnecting the battery for up to a year will not change the mode.

Last Door Closed Locking Mode

There are two last door closed locking modes:

    • Mode 1
        The last door closed locking feature is disabled.
    • Mode 2
        The last door closed locking feature is enabled.

Changing the Last Door Locking Mode

There are two ways to change the last door locking mode:

    • The Tech 2 scan tool method
    • Complete the following steps in order to change the last door locking mode using the Tech 2 scan tool method:
    • At the SELECT SYSTEM screen select BODY.
    • Then select the car line and nameplate.
    • At the APPLICATION MENU screen select PERSONALIZATION.
    • At the next APPLICATION MENU screen select SET OPTIONS.
    • At the next APPLICATION MENU screen select the mode you want.
    • The door lock switch method.

Complete the following steps in order to change the last door closed locking mode using the door lock switch method:

  1. Close all of the vehicle doors.
  2. Turn the ignition switch to the RUN position.
  3. Firmly depress and hold the brake pedal.
  4. Press and hold UNLOCK on either door lock switch.
  5. Hold UNLOCK and complete the following steps:
    6. • Shift the transaxle out of PARK.
    • Shift the transaxle back into PARK.
  6. Complete the following steps in order to change the last door closed locking mode:
    7. • Shift the transaxle out of PARK.
    • Shift the transaxle back into PARK.
  7. The BCM sounds the chime once when the last door closed locking mode is disabled.

    8. The BCM sounds the chime twice when the last door closed locking mode is enabled.

    Release the door lock switch when you obtain the desired mode. Releasing the switch will exit and save the current customization mode.

The last door closed locking mode is enable when the vehicle was manufactured. Disconnecting the vehicle battery for up to a year will not change the mode.

Exit Illumination and Delay Illumination

Refer to Interior Lights Circuit Description in Lighting Systems.