Central Locking System
Central Locking System
From a functional point of view, central locking system on the BMW 1-Series and 3-Series is divided among several control units. The Car Access System (CAS) monitors all the processes in the central locking system. The CAS control unit is the master control unit for the central locking system. The control units for the central locking system are:
- Car access system (CAS)
- Footwell module (FRM)
- Junction Box Electronics (JBE)
Based on the requests from various control points (e.g. lock barrel, remote control, Comfort Access) the CAS control unit decides on:
- Locking/deadlocking the central locking system
- Unlocking the central locking system
Brief component description
The following components supply an input signal for the central locking system:
Door lock cylinder
The door lock cylinder allows mechanical locking/deadlocking and unlocking of the vehicle. If the vehicle electrical system should fail, the driver's door can be unlocked manually with the key (mechanical key element in the ID transmitter).
Remote control
The ID transmitter allows the vehicle to be locked/deadlocked via radio (radio interface). The radio signals from the ID transmitter are received by the remote control service receiver (receiver for ID transmitter) and passed on to the CAS control unit.
The remote control receiver is integrated in the aerial amplifier.
The remote control receiver is integrated in rear view mirror on the convertible.
Central locking button
The central locking button enables the vehicle to be locked/unlocked from inside the passenger compartment. The fuel filler flap is not locked. On the convertible, the glove compartment and the storage compartment in the centre console are not locked.
Hotel position switch (US version)
The hotel position switch is installed in the glove box. The hotel position switch decouples the tailgate from the central locking system. When hotel position is selected (locked or unlocked), the setting of the hotel position switch is detected.
Interior trunk-release button (US version)
The interior trunk-release button on the A-pillar in the driver's footwell allows the trunk to be opened when the vehicle is unlocked and stationary (hotel setting not selected).
Tailgate button on outer tailgate
The exterior boot release button allows the boot lid to be opened when the vehicle is unlocked and stationary (hotel setting not selected).
Tailgate lock
The luggage compartment lock allows the luggage compartment to be mechanically opened (hotel position not selected).
Rear window button
The rear window button can be used to open the rear window if the vehicle is unlocked and stationary. The rear window switch is integrated in the rear window wiper.
The following control units are involved in the central locking system:
CAS: Car Access System
All the rules for controlling the central locking system are integrated in the CAS control unit. The commands are transferred via the body CAN.
JBE: Junction Box Electronics
The junction box electronics are the executing control unit for the central locking system. The junction box electronics handle activation of all the central locking drives. The junction box consists of the junction box electronics and the power distribution box. The junction box is installed under the glove box.
FRM: Footwell module
The footwell module evaluates the status of the Hall effect sensors in the door contacts. When the vehicle is locked or unlocked with the mechanical key element, the footwell module will recognize this request. The footwell module transmits a message on the K‐CAN to the CAS control unit (CAS: Comfort Access System). The footwell module is installed at the A-pillar down in the footwell of the driver's side.
The following actuators are activated by the central locking system:
Door lock
The door locks comprise:
- 2 drives with gearing
- Hall effect sensors as door contact
Drives in the door locks
There are 2 drives in each door lock. The locking mechanism can be brought into the following position by the drives:
- Locking: door can still be opened from the inside
- Deadlock: Door can be opened neither from the outside nor from the inside.
- Unlocking: door can be opened from the inside and outside
Drive for fuel filler flap
The drive locks/unlocks the fuel filler flap.
Drive for the rear lid lock
The drive unlocks the tailgate.
Drive for rear window locking
The drive unlocks the rear window.
Drive for electrically locking glove box
If deadlocking is activated by the central locking, the door lock barrel or the Comfort Access system, the drive motor locks the glove compartment handle.
In this situation, it is only possible to open the glove box with the mechanical key.
If the glove box was locked with the mechanical key, it can only be opened again with the mechanical key.
Drive for electric locking of storage compartment in centre console
The drive locks the storage compartment in the centre console. In the event of a flat or faulty battery, the storage compartment in the centre console can be released in an emergency using a cable assembly.
Release motor for luggage compartment roller cover
There is an release drive on the left and right-hand sides of the D-pillar. To unlock the roller cover for luggage compartment, the release drives are actuated for about 2 seconds by the junction box electronics.
System functions
The central locking system incorporates the following functions:
- Locking
- Deadlocking
- Unlocking
- Hotel setting
- Crash unlocking
- Forced deadlock release
- Lockout protection
- Repeat interlock
- Automatic relocking
- Voltage monitoring
- Selective unlocking
- Speed-dependent locking
- Locking the fuel filler flap
Locking
A locked door cannot be opened from the outside. However, the door can still be opened from the inside. To do this, the inner door handle must be pulled twice. Locking is carried out in the following ways:
- Pressing the central locking button (condition: front doors must be closed)
- Operation via the driver's door lock barrel or the ID transmitter, where the conditions for deadlocking are not fulfilled (see "Deadlocking").
- Driver's door closed
Locking
A deadlocked door cannot be opened from the inside or outside. A door is deadlocked if the vehicle is locked via the drivers door lock cylinder or the remote control. Preconditions:
- Terminal 30B OFF
- Driver's door or front passenger door was opened
- Driver's door closed
When the vehicle is deadlocked, the anti-theft alarm DWA is also primed.
Unlocking
An unlocked door can be opened from the inside and the outside. When the vehicle is unlocked, the alarm system (DWA) is also deactivated.
Hotel position (US version)
When the hotel setting is selected, the tailgate also stays locked after the vehicle is unlocked. For hotel position to be selected, the setting of the hotel position switch is detected.
Crash unlocking
A crash is detected by the ACSM control unit. A crash message is transmitted by the CAS control unit. The message is sent on the K-CAN. The CAS control unit unlocks the vehicle.
All operating points are disabled when there is a crash message. This prevents unintentional actions of the central locking system from occurring due to line short circuits caused by the accident.
After a crash, the central locking cannot be operated again until Terminal 30B has been switched off for at least 3 seconds.
ACSM stands for "Advanced Crash Safety Module", referred to as the crash safety module.
Forced deadlock release
When the CAS detects that a ID transmitter is locked in place in the insertion slot, the central locking system is enabled. The central locking system assumes the "Lock" position. The anti-theft alarm system is also deactivated during forced release.
Lockout protection
To protect the driver against unintentionally locking himself out, all operating points are locked when the driver's door is open. This makes any additional mechanical lockout protection in the door locks unnecessary.
Repeat interlock
To protect the central locking drives (doors, tailgate, fuel filler flap, rear window, glove box and storage compartment in the centre console) against overloading, the CAS monitors repeat operation.
If there are more than 15 attempts at activation within one minute, the drives are not unlocked for a certain time.
Automatic relocking
If the central locking system is unlocked using the ID transmitter and no door or tailgate is opened within 2 minutes, the vehicle is automatically locked again (locked and secured). This function can be activated via the personal profile.
Voltage monitoring
The functional range for the central locking system is specified as being from 9 to 16 volts. Outside of this range, the drives are not activated. If the voltage supply is interrupted, the state of the central locking system does not change (anti-theft protection.).
Selective unlocking
The first time there is an unlocking command, only the driver's door is unlocked. The central locking system sets all other doors from deadlock to lock. The DWA is switched off and the doors remain locked.
With a second unlocking command, the remaining doors are unlocked. This function can be activated in the Personal Profile (depends on national-market version concerned).
Speed-dependent locking
The central locking system is automatically locked from a driving speed of approx. 16 km/h.
This function can be activated in the Personal Profile (depends on national-market version concerned).
Locking the fuel filler flap
The fuel filler flap is only locked when the central locking system is set to deadlock. This function can be activated in the Personal Profile (depends on national-market version concerned).
Notes for Service department
General notes
Nearly all Car and Key Memory functions are programmed inside the vehicle itself. (Please refer to the "Personal profile" section of the Owner's Handbook: Individual settings for a maximum of 3 remote control units via the display in the instrument panel or via the Central Information Display)
National-market versions
National-market version for US
The glove box is electrically locked. Reason: Knee airbag fitted in glove box cover. In order to transmit the forces that are released when the airbags are triggered, the glove box cover is bolted on both sides when it is closed. When the opener is lifted slightly to open the glove box, a microswitch transmits a signal to the junction box electronics (JBE). The JBE briefly actuates the release drive in the glove box. The release drive retracts the 2 locking rods. The glove box cover can then be opened again. After a short time, the release drives are de-energized and the locking rods extend again. The locking rods have an angled area at the ends. This has the effect of mechanically pushing the locking rods against a spring force when the glove box cover is closed. When the glove box cover is closed, the spring force pushes the locking rods back out, locking the glove box.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.