[Yhwsha]

Junction box ELECTRONIC

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Introduction

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.
> E70, E71:
> E81, E82, E87, E88, E89:
> E90, E91, E92, E93:

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 54‐pin connector is for the connection to the dashboard. Two further connectors are for the connection on the main wiring harness. These are 54‐pin and 47‐pin 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.
Note: For current details about the pin assignment and fuse assignment of the junction box electronics and the power distribution box, please refer to the diagnosis system
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 D‐CAN (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 20 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 micro switches are fitted in the second row of seats. The micro switches are used to verify that the second row of seats is correctly locked. The micro switches 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 sun blind for the rear window
The junction box electronics (JBE) actuate the drive for the roller sun blind.
- 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)

Notes for Service department

Observe the following information for service:
- General information:
- Diagnosis: ---
- Encoding/programming: ‐‐‐
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.

[J0hnC0ffie]

Hi Yhwsha,

Thank you very much for this superb post, very interesting.
I'm sorry to bring this 2015 post up but it would be very interesting if any one could share more information on junction box.

From what I know, JBE before march 2007 are using the k-link protocol (OBD) and JBE after are using the d-can protocol.
There is also different versions like L1, L2, H1, H2, H3, H4, KL and M. Does any one knows what is the difference between all those letters?
Maybe a table or PDF documentation with specifications? Some have more relays depending on the car options available but I could not find  any good detail document.

Kind regards,
JC,

[DieStream]

Hello JC, the different version design are for the different body styles.
In my E91(2009), i have a H4 JBBE2. That’s for station wagon.
I want to have a JBBE3R for my E91. That’s the latest JBE for E89X-Series.
If you go to Dealer they sell only the M version, that’s like a Max Brose from the FRM. You can use this version in all body shapes.

[J0hnC0ffie]

Thank you DieStream.

Do you know any ways to correlate the body styles with the JBE?
For instance how to know if the original mount on a e87 is H1 , or Hx ?

That's the kind of document I seek. And I believe that the community could benefit from.

Kind regards,
JC,

[bmchicago]

you can use ETK and supersession for compatible part numbers, and if you have access to ATLAS, you can see forwards and backwards supersessions.