Power Door Locks Description and Operation

POWER DOOR LOCKS DESCRIPTION AND OPERATION

DOOR LOCK SYSTEM COMPONENTS
The power door lock system consists of the following components:
- Driver door lock switch - Uses a single signal wire for both lock and unlock switch activations
- Front passenger door lock switch - Uses a single signal wire for both lock and unlock switch activations
- BCM - Class 2 module which requires programming when replaced
- Reversible door lock actuators in each of the doors
- BCM PWR 15A fuse - Located in the BCM fuse panel, supplies power for the door lock system

DOOR LOCK SYSTEM CONTROLS
The power door lock system can be controlled by any of the following:
- Power door lock switch activation
- Keyless entry lock or unlock command, if equipped
- Delayed locking command
- Automatic door lock command
- Lockout prevention command
- An air bag deployment
- An automatic door lock or unlock actuation.

DOOR LOCK AND UNLOCK OPERATION
The BCM PWR fuse supplies battery positive voltage to the BCM for the door lock system.

The BCM supplies and monitors a reference voltage to the door lock switch through the door lock switch lock/unlock signal circuit. The door lock switch also receives a constant ground source. If a door lock switch is placed in the lock position, the reference voltage is taken directly to ground and the BCM senses 0.0 volts on the signal circuit. If a door lock switch is placed in the unlock position, the reference voltage is taken to ground through a 1.5K ohm resistor that is internal to the door lock switches and senses approximately 2.9 volts on the signal circuit. This is how the BCM determines what portion of the door lock switch was activated.

The BCM, upon receipt of a door lock switch lock or unlock signal, will switch the appropriate door lock actuator control circuits to battery positive voltage. The opposing side of the door lock actuators are connected to ground internally within the BCM through the other door lock actuator control circuit and the doors will lock or unlock appropriately.

Vehicles without keyless entry have two internal drivers in the BCM to control the door lock actuators. All door lock and all door unlock. Vehicles equipped with keyless entry have three internal drivers in the BCM. Driver door unlock, passenger door unlock and all door lock. This is done to isolate the driver door lock actuator so it can be unlocked by itself using the keyless entry transmitter.

AUTOMATIC DOOR LOCK OPERATION
This BCM controlled feature can be personalized to driver preference.

The BCM will automatically lock the vehicle doors if the following conditions exist:
- All vehicles doors are closed.
- The ignition is in the ON position.
- The vehicle is shifted out of PARK.

The BCM will then unlock the doors when the ignition is placed in the OFF position.

DELAYED LOCKING OPERATION
With any door open and a door lock switch is activated in the lock position, the BCM will give three audible chimes. When the door is closed, the BCM will cycle the internal door lock relay to lock the doors after approximately five seconds. This feature can be overridden by activating the door lock switch a second time and the doors will lock even with a door open.

LOCKOUT PREVENTION OPERATION
The BCM will lock all doors and unlock the driver door with a door lock switch lock activation if a vehicle door is open and the ignition key is fully inserted in the ignition. The lockout prevention feature can be overridden if a lock command is received from the keyless entry system.

UNLOCK AFTER AIR BAG DEPLOYMENT
This feature will unlock all of the vehicle doors 15 seconds after an air bag deployment.