Bimmerscan

BMW Junction Box (JBE)

BMW Junction Box - Power Distributor

On the BMW 1 Series, BMW 3 Series and on the BMW X5, the junction box assumes a central role in the vehicle. In the junction box, the power distribution box and junction box electronics form a unit. The junction box electronics is the central gateway in the vehicle.

Brief component description:
The junction box consists of the power distribution box and the junction box electronics.

JBE: Junction Box Electronics
  • The junction box electronics unit combines numerous functions in a single control unit. The junction box electronics unit is connected via 4 plug connections. A 54pin connector is for the connection to the dashboard. Two further connectors are for the connection on the main wiring harness. These are 54pin and 47pin connectors. A 23-pin internal plug connection connects the junction box directly to the power distribution box.
Power distribution box
  • The fuses and various plug-in relays are located in the junction box power distribution box. Depending on the vehicle equipment, the printed circuit boards of the power distribution box are fitted with different relays. There is an opening in the lower part of the junction box. The junction box electronics are connected to the power distribution box through this opening.

Different versions of the power distribution box are fitted, depending on the model series and Model Year measures. For example, the complete fuse assignment may change as part of Model Year measures.

  • 03/2007 Model year measure (not E70, E71): primarily changes to pin assignment.
  • 09/2007 Model year measure (not E70, E71): primarily changes to fuse assignment.

Depending on the vehicle equipment, various relays are mounted on the printed circuit boards in the power distribution box.

System functions

Numerous functions are provided in the junction box electronics (JBE). For example, the junction box electronics process multiple signals, which it makes available to other bus users on the vehicle 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 enable 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
  • Drive train CAN
  • Diagnostic cable or DCAN (diagnosis on CAN)

The Suspension Controller Area Network (F-CAN) is connected to the junction box but is simply looped through. After wake-up, the gateway is ready to send messages over the relevant bus systems within 20Â ms.

– Power window regulator

The footwell module (FRM) and the junction box electronics (JBE) control and monitor the power window regulators. The junction box electronics unit detects the following signals and makes them available to other bus users:

  • Power window switch, front passenger door
  • Power windows switch, right rear door
  • Power window switch, rear door on driver’s side
  • Hall effect sensor, rear door on drivers side
  • Hall effect sensor, rear door on passenger side

The junction box electronics control the following actuators:

  • Power window drive, rear door on passenger side
  • Power window drive, rear door on driver’s side

-Wash/wipe system

The junction box electronics unit detects the following signals and makes them available to other bus users:

  • Front reset contact
  • Rear reset contact

The junction box electronics control the following actuators:

  • Wiper relay for wiper stage 1 and 2
  • Wiper relay for rear window
  • Washer pump relay for headlight-cleaning system

– Central locking system
The junction box electronics (JBE) are the executing control unit for the central-locking system. The junction box electronics handle activation of all the central locking drives. The following control combinations are possible:

  • Selective unlocking
  • Double-unlock
  • Locking Unlocking and deadlock release
  • Deadlocking

The tailgate lock is activated with a separate output stage

– Climate control
The junction box electronics (JBE) unit detects the following signals and makes them available to other bus users:

  • Sensor for automatic air recirculation mode
  • Refrigerant pressure sensor
  • Rear stratification control

The junction box electronics control the following actuators:

  • Auxiliary water pump
  • Control valve for air conditioning system or magnetic coupling
  • Water valve (depending on engine)

– Seat heating
For seat heating, seat-heating electronics or the higher-quality driver’s seat module can be installed. A seat module is always installed with seat memory. The junction box electronics (JBE) send a prompt to determine whether a seat module is installed. If the junction box electronics do not receive confirmation, the junction box electronics handle activation of the seat heating. The junction box electronics generate a pulse-width modulated signal. This signal activates the seat-heating electronics. If a seat module is fitted, the seat heating is activated directly by the seat module.

– Mirror heating and washer jet heating
The junction box electronics (JBE) control the following actuators:

  • Basic version of the mirror heating
  • Washer jet heating

If mirror memory is installed, the footwell module (FRM) controls it via the LIN bus.

– Bi-stable relay
The bi-stable relay is used to shut down the closed-circuit current cutoff relay if there is a standby current violation. Similar to the micro-power module (MPM), e.g. for E60 before 09/2005. The relay is only installed for certain optional equipment (e.g. CCC, M-ASK, TCU, ULF). If a bi-stable relay is fitted, an intelligent battery sensor is also fitted.

– Functions for instrument panel
The junction box electronics detect the following signals for the instrument panel:

  • Fuel level sensor 1
  • Fuel level sensor 2
  • Coolant level
  • Parking brake 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 series 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 panel issues a Check Control message.

– DTC button
The junction box electronics unit detects signals from the DTC button.

– Parking brake switch
The junction box electronics unit detects signals from the parking brake switch.

– Roller sunblind for the rear window
The junction box electronics (JBE) actuate 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”).

– Line connection
As well as its electronic function, the junction box electronics (JBE) also have a connector function. Many of the cables in the 4 connectors connected to the junction box electronics are interconnected via the junction box electronics. The connections optimise the wiring harness. Here, the junction box electronics function as a nodal point.

– Relay of the junction box electronics
The junction box electronics (JBE) have internal and external relays. The excitation coils on all relays are permanently supplied with a positive wire. The positive power supply for the external relays is provided via the load line which is to be switched through. The positive power supply of the internal relay lies on the secured supply line of the junction box electronics. All relays are controlled via the negative lead. All internal relays and the relay for wiper stage 1 and wiper stage 2 are located downstream of the fuse on the current path. All other external relays of the junction box electronics lie in the current path before the fuse.

– Internal relays are:

  • Relay for power window drive, rear
  • Relay for the central-locking drive (except for tailgate)

– The external relays are:

  • Relay for electric motor, rear window wiper
  • Relay for electric motors, wiper stage 1 and wiper stage 2
  • Relay for headlight-cleaning system
  • Relay for heated rear window
  • Bi-stable relay (deactivation of standby current violation)

– Installation location
The junction box with the junction box electronics and the power distribution box is installed behind the glove box below the instrument cluster.

JBE location

BMW E87 JBE location

1. Power distributor in junction box
2. Junction box electronics in the junction box

– Construction
junction box

1. Connector X14270, connector 47-pin
2. Plug to the power distribution box X4010, 23-pin
3. Connector X14271, 54-pin
4. Connector X14272, 54-pin

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