The coach door lock (CoSi) is a necessary safety precaution in the case of vehicles with rear doors that open to the front in the direction of travel. The coach door lock (CoSi) automatically prevents:
Below a vehicle speed of 4 km/h, the coach door lock (CoSi) permits opening of the rear doors by the occupants.
The Car Access System (CAS) incorporates the functions terminal control, electronic vehicle immobilization unit (EWS), remote control signal evaluation.
The door modules register the signals of the switches and sensors installed in the doors and control the drives installed in the doors. Information is received and sent via the K-CAN PERIPHERALS data bus.
The door module in the driver's door is connected to the switch block by a one-wire data bus.
Operated from the switch block in the driver's door:
The door modules in the rear doors (TM-FATH, TM-BFTH) have the following tasks in addition to the functions of the door modules (TM) in the front doors:
In the Car Access System (CAS), the speed threshold of 4 km/h is coded for coach door lock (CoSi) function.
There is a Hall sensor on the inside door handle of the rear door. The Hall sensor registers operation of the inside door handle and transfers the status change to the door module in the rear door.
There is a door contact on the frame of the rear door. The status change that occurs when the rear door is opened and closed (door open = contact closed) is reported to the door module in the rear door.
On the system lock of the rear, the functions controlled by the Car Access System (CAS) and the door module in the rear door are implemented by electromechanical drives:
The status of the elements involved in these functions is determined with the Hall sensors: 'main lock', 'pre-lock', 'CoSi', 'mechanical position of lock', 'SCA standby'.
Note: coach door lock motor (CoSi motor) = child lock motor (KiSi motor)!
Disengagement: The mechanical disengagement of the inside door handle from the system lock prevents opening of the rear door for the functions coach door lock (CoSi) and child safety lock (KiSi). Disengagement takes place with the child lock motor after instruction from the Car Access System (CAS).
Engagement: The mechanical engagement of the inside door handle on the system lock takes place when the inside door handle is operated if the Car Access System (CAS) has enabled activation of the child lock motor.
The coach door lock (CoSi) is engaged when:
Engagement of the coach door lock (CoSi) is triggered by the Car Access System (CAS) by the central locking system (ZV) command ”Activate coach door lock” on the door module in the rear door. To engage the coach door lock (CoSi), the door module energizes the KiSi motor for a defined period.
If the CoSi sensor detects that the coach door lock is engaged, the door module in the rear door sends the signal ”coach door lock active” on the K-CAN SYSTEM data bus.
If the coach door lock (CoSi) is reported as not engaged although it should be engaged, the Car Access System (CAS) makes the door module in the rear door lock the door with the locking motor. The first operation of the inside door handle unlocks the system lock. However, the system lock is immediately locked once again.
If the coach door lock (CoSi) is defective or there is a failure of the Hall sensor for determining the locking of the rear door, the state ”locked” is also created. Locking takes place with the locking (VR) motor of the system lock. The state ”locked” is retained for as long as the coach door lock (CoSi) would prevent opening of the door.
The coach door lock (CoSi) can only be disengaged when the Car Access System (CAS) sends the signal ”Deactivate coach door lock permitted” to the door module in the rear door.
The signal ”disengage CoSi permitted” is issued on the data bus K-CAN SYSTEM when
After the signal arrives, the door module can disengage the coach door lock (CoSi) on operation of the inside door handle.
If the CoSi sensor detects that the coach door lock (CoSi) is disengaged, the door module in the rear door sends the signal ”coach door lock inactive” on the K-CAN SYSTEM data bus to the Car Access System (CAS).
When the door handle is lifted, the handle is mechanically disengaged at the status ”disengage CoSi permitted”. If the door handle is now raised slightly and the Hall sensor is activates, the door module energizes the KiSi motor for the defined period. The same operation takes place when the door handle is let go.
Lifting the door handle again opens the main lock and the pre-lock. This means that the door can be opened the first time the door handle is pulled. If it is pulled too quickly, before the door can be opened the door handle must be released and pulled once again.
The coach door lock (CoSi) is automatically disengaged
When the child safety lock (KiSi) button on the switch block of the driver's door is operated, the Car Access System (CAS) sends the central locking command ”Activate child safety lock” to the door module in the rear door. The door module then runs the following processes on the rear door:
If the child safety lock (KiSi) button is operated again (LED goes out), the Car Access System (CAS) sends the telegrams
to the door module in the rear door.
The door module in the rear door then unlocks the operating options of the power window in the rear door.
The parking brake (EMF) is automatically triggered to brake the vehicle. Here, a closed EMF button is simulated in the door module of the rear door. It is triggered when the following conditions are met:
The Car Access System (CAS) receives from the door module in the rear door the message
In this case, the Car Access System (CAS) sends the command ”Brake” in cycles to the door module.
Note: In the case of ”Driving not permitted” and vehicle speed > 4 km, the CAS issues the error message but no braking takes place!
When the doors are being closed and the ”pre-lock” Hall sensor is activated, the soft-close automatic (SCA) is activated. The soft-close automatic (SCA) draws the door into the system lock. If the door is closed and the soft-close automatic (SCA) has not been activated (e.g. if the door is slammed), the soft-close automatic (SCA) is also activated when the coach door lock (CoSi) is engaged.
If faults are detected in the coach door lock (CoSi) system, the Car Access System (CAS) generates the display of the following text messages on the instrument cluster:
”Door open” for the relevant door if the vehicle speed is ≤ 4 km/h if
”Electronics fault” while the vehicle is being driven at a vehicle speed above 4 km/h if