Power Locks: Description and Operation
Central Locking System
Central locking system
The central locking system is split over several control units, in accordance with function. The Car Access System (CAS) monitors all the processes in the central locking system. The CAS is the master control unit for the central locking system. The following are the control units used for the central locking system:
- Car access system (CAS)
- Footwell module (FRM)
- Junction Box Electronics (JBE)
Brief component description
The following components are described for the central locking system:
- Driver's door lock
- Door contacts
- Master key
- Central locking button
- Rear lid button
- Car access system (CAS)
- Footwell module (FRM)
- Junction Box Electronics (JBE)
Driver's door lock
The driver's door lock allows mechanical locking, securing and unlocking of the vehicle. If the vehicle electrical system malfunctions, the driver's door can be unlocked using the mechanical key in the remote key.
Door contacts
The footwell module (FRM) detects the signals from the door contacts. The FRM forwards the signals over the K-CAN to the junction box electronics (JBE).
Remote control
The remote key allows the vehicle to be unlocked, locked or secured via radio. The radio signals from the remote key are received by the remote control receiver and forwarded to the Car Access System (CAS). The remote control receiver is installed in the inside mirror.
Central locking button
The central locking button allows locking and unlocking from the passenger compartment. It is not possible to use the central locking button for double-unlocking and deadlocking. The central locking button is located in the switch panel centre console, which is integrated into the heating and air conditioning system control panel.
Rear lid button
The outside tailgate pushbutton can be used to open the tailgate if the vehicle is unlocked and stationary.
Car access system (CAS)
All the functions for controlling the central locking system are integrated into the CAS control unit. The commands are transferred via the K-CAN to the junction box electronics (JBE).
Junction Box Electronics (JBE)
The JBE is the activating control unit for the central locking system. The JBE handles activation of all the central locking drives. The JBE consists of the junction box electronics and the power distribution box. The junction box is installed under the glove box.
Footwell module (FRM)
The footwell module (FRM) assesses the status of the door contacts. The FRM identifies the request when the mechanical key is used to lock or unlock the vehicle. The FRM transmits a message to the CAS via the K-CAN. The FRM is installed on the A-pillar in the driver's side footwell.
System functions
The following system functions are described for the central locking system:
- Locking
- Deadlocking
- Unlocking
- Crash unlocking
- Forced deadlock release
- Lockout protection
- Repeat interlock
- Automatic relocking
- Voltage monitoring
- Selective unlocking
- Speed-dependent locking
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 when:
- the doors are closed.
- the central locking button is operated.
- the remote key is operated.
- the driver's door lock is operated.
Deadlocking
A deadlocked door cannot be opened from the inside or outside. The deadlocking function is executed when locks are engaged either at the driver's door lock or using the remote key. Operations for deadlocking:
- Terminal R OFF
- Driver's door or front passenger door was opened
- Driver's door closed
When the vehicle is deadlocked, the alarm system (DWA) is also activated.
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. If the power supply malfunctions, the driver's door can be unlocked using the mechanical spare key in the remote key.
Crash unlocking
A crash is detected by the multiple restraint system (MRS). A crash message is transmitted to the CAS. The message is sent on the K-CAN. The CAS 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. The central locking system can only be reactivated after a crash once terminal R has been switched off for at least 3 seconds.
Forced deadlock release
When the CAS detects that a remote key is locked in place in the insertion slot, the central locking system is unlocked. 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 from overloading, the CAS monitors repeated operation. The doors, tailgate and fuel filler flap are monitored. If there are more than fifteen operations within one minute, the electric motors are not unlocked for a certain time.
Automatic relocking
If the central locking system is unlocked using the remote key and no door or tailgate is opened within two minutes, a locking procedure is automatically carried out again.
Voltage monitoring
The functional range for the central locking system is specified as being from 9 to 16 volts. The drive units are not activated outside this range. 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. At all other doors the central locking system switches from deadlocking to locking. The DWA is switched off and the doors remain locked. The remaining doors are unlocked when the unlocking command is given a second time. The function can be activated over the Car & Key Memory (dependent on the national-market version).
Speed-dependent locking
The central locking system is automatically locked from a driving speed of approx. 16 km/h. This function can be activated over the Car & Key Memory.
Notes for Service department
Nearly all Car and Key Memory functions are programmed inside the vehicle itself.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.