System functions
Numerous functions are provided in the junction box electronics (JBE). For example, the junction box electronics unit processes multiple signals, which it makes available to other bus subscribers on the electrical system. It also performs control tasks.
Depending on the model series and equipment, the following functions can be controlled or signals detected by the junction box electronics:
- Gateway
The junction box electronics unit enables a number of bus systems to communicate with one another. The junction box electronics unit provides the gateway function for the following bus systems:
- Body CAN
- Powertrain CAN
- Diagnosis wire or D-CAN (diagnosis-on CAN)
The chassis CAN (F-CAN) is connected to the junction box, but is merely looped through.
After waking, the gateway is ready to send messages to the corresponding bus systems within 20 ms.
- Power windows
The footwell module (FRM) and the junction box electronics (JBE) control and monitor the power windows.
The junction box electronics detects the following signals and makes them available to other bus subscribers:
- Power window switch, front passenger door
- Power window switch, rear door on the front-passenger side
- Power window switch, rear door on the driver's side
- Hall sensor, rear door on the driver's side
- Hall sensor, rear door on the front-passenger side
The junction box electronics unit controls the following actuators:
- Power window drive, rear door on the front-passenger side
- Power window drive, rear door on the driver's side
- Wiper/washer system
The junction box electronics unit detects the following signals and makes them available to other bus subscribers:
- Reset contact, front
- Reset contact, rear
The junction box electronics unit controls the following actuators:
- Wiper relay for wiper stage 1 and 2
- Wiper relay for rear window
- Windscreen washer pump relay for headlamp wipe/wash unit
- Central locking system
The junction box electronics (JBE) is the executing control unit for the central locking system. The junction box electronics assume the task of actuating all central-locking system drives. The following control combinations are possible:
- Selective unlocking
- Deadlock release
- Locking
- Unlocking and deadlock release
- Deadlocking
The boot lid lock is activated via its own output stage.
- Climate control
The junction box electronics (JBE) detect the following signals and makes them available to other bus subscribers:
- Sensor for automatic air recirculation mode
- Refrigerant pressure sensor
- Rear stratification control
The junction box electronics unit controls the following actuators:
- Additional coolant pump
- Control valve for air-conditioning system or magnetic coupling
- Water valve (depends on engine equipment)
- Seat heating
A seat heating module or the more advanced driver's seat module can be fitted for the seat heating. A seat module is always fitted with seat memory.
The junction box electronics unit (JBE) sends a request to check whether a seat module has been fitted. If the junction box electronics unit does not receive a confirmation, the JBE will take over control of the seat heating. The junction box electronics generate a pulse-width-modulated signal. This signal is used to control the seat heating module.
If a seat module has been fitted, the seat heating is controlled directly by it.
- Mirror heating and heated washer jets
The junction box electronics (JBE) control the following actuators:
- Basic variant of mirror heating
- Heated washer jets
If a mirror memory has been fitted, the LIN bus takes over control of the footwell module (FRM).
- Bistable relay
The bistable relay is used to shut down terminal 30g-f if there is a closed-circuit current fault. Similar to the micro power module (MPM), e.g. for E60 before 09/2005.
The relay is built in for certain options only (e.g. CCC, M-ASK, TCU, ULF). If a bistable relay is fitted, an intelligent battery sensor will also be fitted.
- Functions for instrument cluster
The junction box electronics unit detects the following signals for the instrument cluster:
- Fuel level sensor 1
- Fuel level sensor 2
- Coolant level
- Parking brake warning switch
- Washer fluid level
- Lock for second row of seats
- E70
The junction box electronics (JBE) monitor the locking of the second row of seats.
A total of 5 microswitches are fitted in the second row of seats. The microswitches are used to verify that the second row of seats is correctly locked. The microswitches are wired in parallel directly with the junction box electronics.
When the second row of seats is correctly locked, a signal is sent to the junction box electronics. If the signal is not received, the second row of seats is not correctly locked. The junction box electronics sends a message on the body CAN. The instrument cluster emits a Check-Control message.
- DTC button
The junction box electronics unit detects signals from the DTC button.
- Parking brake warning switch
The junction box electronics unit detects signals from the parking brake warning switch.
- Roller sunblind for rear window
The junction box electronics actuates the drive for the roller sunblind.
- Servotronic valve
On vehicles with Servotronic, the junction box electronics actuates the Servotronic valve (only on vehicles without option 217 "Active Steering").