GM Service Manual Online
For 1990-2009 cars only

Door Lock System Components

The power door lock system consists of the following components:

    • LF door lock switch
    • RF door lock switch
    • Liftgate lock/unlock release switch, if equipped
    • Door lock relay
    • Door unlock relay
    • Driver door unlock relay, w/ keyless entry
    • Body Control Module (BCM)
    • Reversible door lock actuators in each of the front doors
    • Reversible door lock actuator in the side door
    • Reversible door lock actuator in the cargo door or liftgate
    • CIG LTR 20A fuse (switch supply voltage)
    • PWR ACCY 30A circuit breaker (relay supply voltage)

Door Lock System Controls

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

    • A power door lock or unlock switch activation
    • A keyless entry transmission
    • A BCM delay lock function
    • A BCM lockout prevention function

Driver and Passenger Door Lock Operation - w/o Keyless Entry

When any of the door lock switches are placed in the lock position, voltage is applied to the door lock control circuit and the lock relay winding. Since the other side of the lock relay winding is connected to ground, the relay is energized. This causes the contacts to close and complete the path from the PWR ACCY circuit breaker through the battery voltage circuit. Voltage is then applied to the lock side of the door lock actuators. Since the other side of the all the door lock actuators are connected to the normally closed contacts of the unlock relay to ground , the doors lock.

The lock function can also be accomplished by the BCM supplying voltage to the door lock control circuit by a delay lock function.

Driver and Passenger Door Lock Operation - w/ Keyless Entry

When any of the door lock switches are placed in the lock position, voltage is applied to the door lock control circuit and the lock relay winding. Since the other side of the lock relay winding is connected to ground, the relay is energized. This causes the contacts to close and complete the path from the PWR ACCY circuit breaker through the battery voltage circuit. Voltage is then applied to the lock side of the door lock actuators. Since the other side of the passenger door, cargo door or sliding side lock actuators are connected to the normally closed contacts of the unlock relay to ground and the driver door lock actuator is connected to the normally closed contacts of the driver door unlock relay to ground, the doors lock.

The lock function can also be accomplished by the BCM supplying voltage to the door lock control circuit by any of the following:

    • A keyless entry lock transmission
    • A delay lock function

Driver and Passenger Door Unlock Operation - w/o Keyless Entry

When any of the door lock switches are placed in the unlock position, voltage is applied to the door unlock control circuit and the unlock relay winding. Since the other side of the unlock relay winding is connected to ground, the relay is energized. This causes the contacts to close and complete the path from the PWR ACCY circuit breaker through the battery voltage circuit. Voltage is then applied to the unlock side of the door lock actuators. Since the other side of the door lock actuators are connected to the normally closed contacts of the lock relay to ground, the doors unlock.

Passenger Door Unlock Operation - w/ Keyless Entry

When any of the door lock switches are placed in the unlock position, voltage is applied to the door unlock control circuit and the unlock relay winding. Since the other side of the unlock relay winding is connected to ground, the relay is energized. This causes the contacts to close and complete the path from the PWR ACCY circuit breaker through the battery voltage circuit. Voltage is then applied to the unlock side of the door lock actuators. Since the other side of the passenger(s) door lock actuators are connected to the normally closed contacts of the lock relay to ground, the doors unlock.

The unlock function can also be accomplished by the BCM supplying voltage to the door lock control circuit by a keyless entry unlock transmission.

Driver Door Unlock Operation - w/ Keyless Entry

The driver door unlock control circuit uses a dedicated driver door unlock relay. This is done so that the driver door may be unlocked by itself using a keyless entry unlock transmission. The driver door unlock relay differs slightly from the unlock relay in that the primary side of the relay is connected to the PWR ACCY circuit breaker and the door unlock control circuit is pulled low by the BCM to energize the relay.

When any of the door lock switches are placed in the unlock position, a voltage is applied to the unlock relay and to the BCM. When the BCM senses the voltage signal, it grounds the driver door unlock control circuit. Since the other side of the driver door unlock relay winding is connected to the PWR ACCY circuit breaker through the battery voltage circuit, the relay is energized. This causes the contacts to close and complete the path from the PWR ACCY circuit breaker through the battery voltage circuit. Voltage is then applied to the unlock side of the driver door lock actuator. Since the other side of the driver door lock actuator is connected to the normally closed contacts of the lock relay to ground, the driver door unlocks.

Liftgate Lock/Unlock Release Switch Operation

On vehicles equipped with a liftglass and dutch doors, the liftgate lock/unlock release switch (mechanical key) is added to serve the same function as the front power door lock switches. By inserting the door key into the liftgate lock/unlock release switch and turning the key to the lock or unlock positions, voltage is applied to the door lock or unlock control circuits to control the lock or unlock relays. This will lock or unlock all of the doors, including the dutch doors. Once the door lock system is unlocked, press the liftgate release switch to electrically open the liftglass and pull the handle to open the secondary latch.

For further information about the liftgate release system, refer to Rear Hatch/Gate Description and Operation in Body Rear End.

Delay Locking Operation

This feature allows the operator to lock all the doors from any door lock switch or a keyless entry lock transmission with the side door open. The sliding side door has contact plates that complete the power door lock and unlock fuse supply circuits when the sliding side door is closed, and interrupt these circuits when the sliding side door is open. When a lock function occurs and the BCM senses an active state on the sliding side door ajar switch signal circuit (door open), the driver, passenger and cargo doors will lock as described, and the BCM continues to monitor the sliding side door ajar switch signal circuit . When the BCM senses an inactive state (door closed), the BCM will cycle the door lock relay again after approximately 5 seconds to perform another lock function, thus locking the sliding side door.

Lockout Prevention Operation

This feature prevents the locking of the driver door if the ignition key is left in the ignition lock cylinder. If a lock function occurs from any door lock switch and the BCM senses an active state on either the left front door latch signal, secondary door latch switch signal and/or the lift gate ajar switch signal circuits and the key in ignition switch signal circuit is in the yes state, the BCM will cycle the door lock relay to lock the doors and then cycle the driver door unlock relay to unlock the driver door.

Programmable Automatic Door Locks

The automatic door lock feature can be programmed to control the door lock system. The automatic door lock feature is factory programmed to have all doors lock and unlock. For detailed instructions on programming the automatic door locks, refer to Vehicle Personalization in Personalization.

When the automatic door lock feature is programmed to control the door lock system, the BCM will lock the vehicle doors if the following inputs are true:

    • Ignition 1 input is active.
    • All door jamb switch inputs are inactive.
    • Cargo door or lift gate/lift glass ajar inputs are inactive.
    • Transmission is shifted out of park

This automatic door lock function will only occur once per ignition cycle unless, a door jamb switch input changes state to active and back to inactive. Then the BCM will lock all doors again.

Once the automatic door lock feature has locked the doors, the BCM will then unlock all the doors when the transmission is shifted into park.