For 1990-2009 cars

The automatic door lock system has several features, controlled by the Body Control Module (BCM), which are listed below. The door lock switches and the door lock cylinder tamper switch sends an input to the BCM. The BCM then controls the door lock and actuators through relays.

### Automatic Door Lock/Unlock

When the ignition is in the RUN position, all doors are closed, and the vehicle is shifted out of park, the BCM will lock all the doors. When the vehicle is shifted into park, all doors will unlock. The unlock portion of this feature can be disabled either by using the TECH 2, or by key FOB sequence. Refer to Programming the Receiver in wiring systems.

### Central Door Unlock

The central door unlock feature is performed using the key in the door lock cylinder. As the key is rotated, the driver's door is unlocked. If the key is held in the unlock position for more than 1.5 seconds, all the doors will unlock.

### Anti-Lockout Feature

If any door is opened and the key is in the ignition cylinder, the BCM will not lock the doors when the door lock switch is pressed. This prevents the keys from being locked in the car. If the door lock switch is held for more than three seconds, this feature will be overridden and the doors will lock.