GM Service Manual Online
For 1990-2009 cars only

Lock/Unlock

The driver door lock switch lock and unlock signal circuits provide input to the driver door module (DDM) when the driver door switch is activated to the LOCK or UNLOCK position. These inputs allow the DDM to detect a door lock or unlock request. The DDM provides both power and ground to the driver door lock and unlock switches. When the driver door lock switch is activated, a ground is supplied through the driver door switch to the driver door lock input which is pulled low. When the DDM detects low voltage on the driver door lock input, the DDM will lock the driver door. The DDM will also send a message on the serial data line to the passenger door module (PDM) to lock the passenger door. When the driver door unlock switch is activated, the DDM will unlock the driver door and also send a message on the serial data line to the PDM to unlock the passenger door. The passenger door lock and unlock function operates the same as the driver door except when the PDM detects low voltage on the passenger door lock input, the lock or unlock message is sent to the DDM. Both door modules provide output control to their respective door lock motors based upon a lock or unlock switch input, or from a message received on the serial data line from the other door module. The door modules provide both power and ground through the door lock actuator unlock control, driver door lock actuator unlock control and the door lock actuator lock control circuits to the door lock motors. The lock and unlock output operation is similar to each other except that the polarity of the voltage applied to the door lock motors is reversed.

Automatic Lock

If the AUTO LOCK-ON feature is selected, the vehicle will automatically lock both doors when the transmission is shifted out of PARK. In manual transmission vehicles, both doors will lock when the vehicle exceeds 16 km/h (10 mph).

The AUTO LOCK-OFF feature will disable the automatic lock function.

For information on enabling or disabling the automatic door locks refer to Vehicle Personalization in Personalization.

Automatic Unlock

If the AUTO UNLOCK-DRIVER feature is selected, the vehicle will automatically unlock the driver door when the ignition is turned OFF and the key is removed from the ignition.

If the AUTO UNLOCK-BOTH feature is selected, the vehicle will automatically unlock both doors when the ignition is turned OFF and the key is removed from the ignition.

The AUTO UNLOCK-OFF feature will disable all automatic unlock functions.

For information on enabling or disabling the automatic door unlock feature refer to Vehicle Personalization in Personalization.