Power Locks: Description and Operation
Power Door Locks Description and Operation
Door Lock System Components
The Power Door Lock System consists of the following components:
* Body control module (BCM)
* Driver door lock switch
* Front passenger door lock switch
* Reversible door lock actuator in each of the doors
* IBCM (PWR) 15-amp fuse
* Driver door cylinder switch, if equipped
Door Lock System Controls
The Power Door Lock System is controlled by the body control module (BCM) and can be activated by any one of the following:
* A door lock switch lock or unlock actuation
* A keyless entry transmitter actuation
* An automatic door lock or unlock actuation
* A last door closed locking (LDCL) actuation
If the driver door cylinder switch feature of the vehicle is functional, the locks may also be operated by a driver door cylinder switch lock or unlock activation
Power Door Lock Switch Operation
Each door lock switch is wired to the body control module (BCM) through a separate door lock/unlock signal circuit. While these circuits are separated between the BCM and respective door lock switch, they are connected into a single circuit within the BCM. The BCM supplies voltage through the door lock/unlock signal circuits to each door lock switch. When either door lock switch is operated, this supply voltage is pulled to ground, providing the BCM with the required lock or unlock signal. In order for the BCM to distinguish between a lock and unlock signal, the lock switch contains two separate paths for this voltage to flow to the same body ground. When the switch is operated to the unlock position, the supply voltage flows to ground through a 1.5 Kohm resistor. When the switch is operated to the lock position, the supply voltage flows to ground through a different part of the switch circuit, which has no resistor. The BCM then interprets the flow of voltage as a lock or unlock request and powers the door lock actuators to the appropriate lock or unlock position.
Power Door Lock Actuators
The body control module (BCM) powers the reversible door lock actuators by providing battery positive voltage and ground to the appropriate lock and unlock control circuits of the actuators. The Lock control circuits of the driver and passenger door lock actuators are all connected together, however, the Unlock control circuits are connected in a slightly different way. While the unlock control circuits for the passenger door lock actuators are connected together, the driver door lock actuator has a separate unlock control circuit. The system is designed this way so that the keyless entry transmitter may be used to unlock only the driver door. Despite this difference, all of the lock actuators perform much the same way. When the door lock actuators are not active, all actuator Lock and Unlock control circuits are at ground potential within the BCM. Transitioning of the lock actuators to the lock or unlocked position depends upon which control circuits receive voltage and which control circuits receive ground.
* If the BCM is commanding the door lock actuators to Lock, it momentarily switches the lock control circuits to voltage. Since the unlock control circuits are at ground potential within the BCM, the actuators transition to the Lock position.
* If the BCM is commanding all door lock actuators to Unlock, it momentarily switches the unlock control circuits for both the driver and passenger door lock actuators to voltage. Since the lock control circuits are at ground potential within the BCM, all lock actuators transition to the Unlock position.
* If the BCM is commanding only the driver door lock actuator to Unlock, it momentarily switches only the driver door actuator unlock control circuit to voltage. Since the lock control circuit is at ground potential within the BCM, the actuator transitions to the Unlock position.
Power Door Lock and Unlock Operation w/Keyless Entry Transmitter
The keyless entry transmitter may be used to unlock only the driver door. When the unlock button of the keyless entry transmitter is pressed once, the body control module (BCM) receives the unlock request from the remote control door lock receiver (RCDLR). The BCM interprets this single press as an unlock driver door request and responds by switching only the driver door lock actuator unlock control circuit to voltage. With the lock actuator lock control circuit for the driver door at ground potential within the BCM, the driver door lock actuator transitions to Unlock.
If the unlock button of the keyless entry transmitter is pressed a second time within three seconds of the first press, the BCM interprets this second press as a request to unlock the passenger doors and responds by switching the passenger door unlock control circuits to voltage. With the lock actuator lock control circuits at ground potential within the BCM, the passenger door locks transition to Unlock.
To lock all doors with the keyless entry transmitter, a single press of the transmitter lock button is all that is ever needed. The BCM receives the lock doors request from the RCDLR and responds by switching all lock actuator lock control circuits to battery voltage. With the actuator unlock control circuits at ground within the BCM, all actuators transition to Lock.
Lockout Prevention
This function is intended to prevent the vehicle operator from locking the doors if the key is left in the ignition and any vehicle door is open. The lockout prevention function can be overridden by the body control module (BCM) if the BCM receives a door Lock input for longer than 3 seconds.
Automatic Door Lock/Unlock
The automatic door lock/unlock function is a vehicle personalization feature with the following 4 programmable modes of operation:
1. All of the doors lock when the vehicle is shifted out of Park with the ignition ON.
2. All of the doors lock when the vehicle is shifted out of Park with the ignition ON, and all of the doors Unlock when the vehicle is shifted into Park.
3. All of the doors lock when the vehicle is shifted out of Park with the ignition ON, and only the driver door Unlocks when the vehicle is shifted into Park.
Last Door Closed Locking (LDCL)
The last door closed locking (LDCL) function is a vehicle personalization feature that is intended to allow the doors to be locked while passengers are exiting the vehicle. When LDCL is in Active Mode, the body control module (BCM) will delay locking of the vehicle doors for 5 seconds after all of the doors have been closed. The LDCL function will be overridden if the BCM receives a door Unlock input or a key in ignition input.