GM Service Manual Online
For 1990-2009 cars only

All Door Unlock

Pressing UNLOCK once on either door lock switch sends a ground signal to the BCM through the door lock/unlock input circuit. The door lock/unlock input signal causes the BCM to supply voltage to the power door unlock feed circuits and the BCM also supplies ground to the power door lock feed circuits for 300 ms. The voltage and ground that is supplied, energizes all of the door actuators and unlocks all of the doors.

All Door Lock

Pressing LOCK once on either door lock switch sends a ground signal, through a 470ohms resistor, to the BCM through the door lock/unlock input circuit. The door lock/unlock input signal causes the BCM to supply ground to the power door unlock feed circuits and the BCM also supplies voltage to the power door lock feed circuits for 300 ms. The voltage and ground that is supplied, energizes all of the door actuators and locks all of the doors.

Driver Door Unlock

Pressing UNLOCK once on the keyless entry transmitter sends a message from the RCDLR to the BCM through the communication link circuit. This message will cause the BCM to supply voltage to the driver power door unlock feed circuit and the BCM will also supply ground to the power door lock feed circuits for 300 ms. The voltage and ground that is supplied, energizes the driver door actuator and unlocks the driver door.

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 Vehicle Personalization/Customization in Entertainment for more information.
    • A vehicle door is open.
        An open vehicle door causes a ground signal to the BCM door ajar input.
    • The key is removed from the ignition switch. This action disables lockout prevention.
        When the key is removed from the ignition switch, an open occurs to the BCM, key in ignition, input.
    • When LOCK is pressed once on a door lock switch or keyless entry transmitter, the BCM locks all of the doors 4.5-5.5 seconds after all of the doors are closed.

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 to the BCM door ajar input.
    • The key is fully inserted in the ignition switch cylinder.
        Full insertion of the key causes a ground signal to the BCM (key in ignition input).

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 Vehicle Personalization/Customization in Entertainment for details.
    • The ignition switch is in the ON position.
    • A transaxle range PRNDL signal is transmitted from the PCM to the BCM via the Class 2 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 to the BCM (door ajar input).
    • The ignition switch is in the ON position.
    • A transaxle range PRNDL signal is transmitted from the PCM to the BCM via the Class 2 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 to the BCM (door ajar input).
    • The ignition switch is in the ON position.
    • A transaxle range PRNDL signal is transmitted from the PCM to the BCM via the Class 2 serial data link. The transaxle is shifted out of PARK or NEUTRAL.