General Information

Central Locking

Purpose of the System

The Central Locking System provides locking/unlocking of the entire vehicle from one central exterior point. From the driver's door or the remote (key-less) entry, a lock/unlock request will lock/unlock all exterior doors, luggage compartment and the fuel filler flap.

From inside, the vehicle can be locked/unlocked using a central locking button located in the center console. Individual doors can be unlocked manually by pulling twice on the interior door handle.

From 2000 MY - if the vehicle has been double locked, press the central locking button and pull the interior door handle twice (alarm will sound when the door opens).

Locking the vehicle from the central switch will "single lock" all doors, luggage compartment and not lock the fuel filler flap.

The Central Locking System utilizes the GM III and Door Modules to carry out all of the locking/unlocking features:
- Remote (key-less) entry is standard.
- When locked from the outside, the vehicle will double lock and arm the DWA System. The ignition must be switched off and the driver's door must be opened and closed.
- Selective unlocking from the outside of the vehicle. Unlocking from the driver's door or remote transmitter will only unlock the driver's door and disarm the DWA System. A second request will unlock the remaining doors and luggage compartment. This feature can be modified for individual users in Key Memory to open all doors from a single request.
- A single central locking button is installed in the center console that will operate when all of the doors are closed. Locking the vehicle from the central switch will "single lock all doors, luggage compartment and not lock the fuel filler flap. When unlocking, a single request will unlock the driver's door only. This feature can be modified for individual users in Key Memory to open all doors and luggage compartment from a single request.
- A remote luggage compartment button is installed in the left kick panel (center console in the E53) to open the luggage compartment from inside the vehicle.
- The EWS is interfaced for double lock monitoring and unlock function. With the presence of an accepted EWS key in the ignition, the vehicle will be unlocked arid disarm DWA.
- The automatic locking feature ( > 99 MY) activates the door locks when a road speed signal of 5 MPH and engine RPM is detected via the K-Bus. The factory default setting of this feature is off (can be encoded on for individual users with Key Memory function).
- In the event of an accident (ignition on), the GM will be signalled to unlock all doors.

Hardware Features:




- The external lock cylinders are located in the driver's door and luggage compartment lid (E53/E39 Sport Wagon does not have a tailgate lock cylinder).
- The driver's door and luggage compartment incorporates an overrunning lock cylinder. The lock cylinder will free wheel or spin. If any key other than the vehicle key or tool, such as a screw driver, is inserted into the cylinder. The lock cylinders can be manually locked/unlocked by turning the key "past" lock/unlock.




- The door lock buttons are mechanically uncoupled from the lock actuators when locked.
The door lock buttons "mechanically" lock the individual doors. This provides manual locking in the event of a central locking malfunction.






- Child safety locks (located in the rear doors) are actuated by inserting a key in the slot on the door latch or by sliding a lever (dependent on model).
The door can now only be opened from outside.




- The luggage compartment can be manually locked with a "Master Key" and leaving the lock cylinder in the horizontal position which prevents opening by any other method (secured for valet).
The luggage compartment release button inside the vehicle will also be ignored by the GM.
Prior to 2000 MY the vehicle could be locked/unlocked using the luggage compartment lock cylinder.




- The glove box has a lock cylinder to secure the contents by manual locking with a "Master Key" and leaving the lock cylinder in the horizontal position which prevents opening by any other method (secured for valet).
- The E38 has a lever behind the glove box handle which permits locking the glove box without a key. Opening still requires a key.

The valet key is not mechanically capable of entering either of these lock cylinders.




- The Fuel Filler Flap mechanical release is found in the right side of the luggage compartment.
The "pull tether" is behind the button as shown on the right.


NOTE: Continuous operation of locking/unlocking will cause a timed arrest of the locking system. When activated, the timed arrest lasts for 2 minutes (or recycle the ignition KL15). The "crash" signal will override the timed arrest and unlock the vehicle.


System Components - with the Principle of Operation




Driver's Door Lock: The lock/unlock signals from the driver's door lock cylinder are input to the driver's door module from the two microswitches on the lock cylinder. The driver's door switchblock module carries out the locking function of the driver's door.

The windows and sunroof can be closed or opened by holding the key in the lock/unlock position (convenience closing/opening feature).

The signal to lock the remaining doors and fuel filler flap is passed over the P-Bus to the GM III and passenger's door module. The locking of the passenger's door is carried out by the passengers door module. The rear doors, luggage compartment and fuel flap locking are carried out directly by the GM III. All four doors will be pulled into the double lock position when locking from the driver's door.

The control of the actuators in the front doors is through final stages in the door modules. The rear doors, trunk and fuel filler flap actuators are controlled by internal relays in the GM III. When locked, the GM III will not carry out any opening commands front the central locking button or luggage compartment interior release button.

Luggage Compartment Lock Cylinder (except E53/E39 Sport Wagon): The vehicle can be locked/unlocked (prior to 2000 MY) from the luggage compartment lock cylinder The lock/unlock microswitch inputs are processed in the GM III and the locking commands are carried out.




The signal is passed over the P-Bus to the door modules to lock/unlock the front doors and the GM III locks the rear doors and fuel filler flap.

All door actuators are placed in the double lock position. Removing the key in the horizontal position will activate the valet mode and prevent the valet key from opening the luggage compartment.

Luggage Compartment Remote Unlock:




The luggage compartment can be opened from inside the vehicle with the remote release button. This feature is also functions when the doors are locked from the central button.

The GM will disregard the remote release button input when the luggage compartment is mechanically locked with the Master Key (valet setting).

The GM will also disregard the release input if the vehicle speed is > 4 MPH.

The E53 remote release button is located in the center console. This input will release the rear liftgate following the same criteria stated above.

Crash Signalling
The Multiple Restraint System (MRS) control module provides a switched signal to the GM in the event of an accident. This signal was previously provided by the crash sensor located in the left front kick panel ( < 9/96 MY).







The signal is an output function of the MRS control module and becomes active when MRS determines a crash has occurred. The GM unlocks the vehicle, switches on the interior lights and flashes the exterior lights when this signal is active.

System Components: Inputs - Processing - Outputs







Door Lock Actuators: A door lock actuator contains an electric motor and an integrated microswitch (position switch).The rotary motor movement through the gear drive mechanically moves the locking latch.

When the lock actuator is operating, the motor is powered until the position switch signals the "locked" position. If the vehicle is locked from the exterior, the motor is powered further and the the gear mechanism is moved beyond the locked position into the "double lock" position. The motors must be powered (in reverse) to release the double lock. The inside door handles will not unlock a "double locked" vehicle.

E53 Door Lock Mechanism: The E53 utilizes a door latch combined with dual actuator motors. This type of actuator is sealed, self contained units with no replaceable parts. The door lock actuators use hall effect sensors in place of pin contacts/microswitches to provide:




- Door lock key position (driver's door only)
- Door open/closed status (replaces door jamb switch).

The GM monitors the lock cylinder positions over two wires. The signals are generated by two hall effect sensors (Hall Sensor 1 & 2) located in the actuator.

When the key is turned, a plastic cylinder in the lock actuator is simultaneously rotated by the lock tumbler extension rod.

An asymmetrical shaped magnet is incorporated in the plastic cylinder, which when rotated changes the magnetic influence on the hall sensors. The presence of a magnet in close proximity to the sensing surface of either hall sensor creates a coded input over the two wires that the GM uses to determine the key position.
- Magnet in front of sensor, current flow through the sensor is < 5 mA (0).
- Magnet rotated away from sensor, current flow through the sensor is > 12 mA (1).

Hall effect sensors improve the actuators reliability since they are impervious to moisture and there are no wear contacts.




- Key in the neutral position, both sensors are simultaneously influenced by the magnet - 0/0.
- Key turned to the unlock position from neutral, hall sensor #1 magnet segment moves away from hall sensor - 1/0.
- Key turned to lock position from neutral, hall sensor #2 magnet segment moves away form hall sensor - 0/1.

There are two motors incorporated in each actuator that provide two separate functions:

Single lock/unlock function




Also known as central lock, this motor controls the mechanical lock mechanism when the central lock button is pressed to single lock the vehicle.

The lock mechanism is fully locked at this point but can still be opened from the interior by pulling the appropriate interior door handle twice or by pressing the central lock button again. When single lock function is activated, the fuel filler flap actuator is not locked.

Double lock/unlock function




Also known as central arrest, this motor is activated only when the vehicle is locked from the exterior at the driver's door lock with a key or when the GM receives a lock request from the Key-less entry system. In this case the double lock motor is activated simultaneously with the single lock motor.

The function of the double lock motor is to mechanically offset an internal rod disabling it from unlocking the vehicle from the interior. This prevents the doors from being unlocked by any means except from an unlock request at the driver's door or via the Key-less entry.

Door Contact Hall Sensor







Also included in the drivers door actuator is a third hall effect sensor. This sensor signals the door open/closed status to the GM. This sensor replaces the door jamb mechanical switch of previous systems. The rotary latch plate position activates the door contact hall sensor.
- When the door latch is closed, current flow through the sensor is < 5 mA (0).
- When the door is open, current flow through the sensor is > 12 mA (1).

The passenger side front door and both rear door lock actuators only include this hall effect sensor (hall sensor 3). Hall sensors 1 & 2 are not required.