On-Board Computer Functions

Power Supply JBE Junction Box Electronics

JBE minimum function:
The junction box electronics (JBE) are located in the bottom of the distribution box (SV). The JBE (A04010a) and distribution box together are referred to as the junction box (A04010). As soon as the junction box electronics are able to communicate with the diagnostic system, the following power supply is present:
- Diagnostic lead via connector X14271
- Ground connection via connector X14270
- Power supply (unfused) from distribution box via the internal connector X04010. The processor and CAN bus communication gateway function (between PT-CAN and K-CAN) of the JBE are supplied across this cable.
- Power supply (fused via F63) from the distribution box via the internal connector X04010. All other functions of the JBE are supplied across this cable. Exceptions are the drives that are switched by the JBE via relays.

Relays of the JBE (internal and external):

Functions of internal relays (in JBE):
- Drives for rear power windows (F62/F64)
- Drives for central-locking system (F56/F57), except luggage compartment lid and rear window

Functions of external relays (on distribution box):
- Drive for rear window wiper
- Drive for wiper stage 1 and wiper stage 2
- Pump for headlight-washer system
- Activation of rear window defroster
- Bistable relay (cutoff with closed-circuit current faults)

All the relay coils of the relays of the JBE (internal and external) are continuously supplied by a positive cable. The positive power supply of the relay coils of the external relay comes from the through-switching load circuit. The positive power supply of the relay coils of the internal relay comes from the fused power supply line of the JBE (F63). All relays of the JBE (internal and external) are controlled via the negative cable.

All the internal relays of the JBE and the relays for wiper stage 1 and wiper stage 2 are located in the current circuit behind the fuse. All other external relays of the JBE are located in the current circuit in front of the fuse (relay sound also in the event of a defective fuse).

Bus connections:
The JBE is connected to the PT-CAN and the K-CAN. The JBE is the gateway for these buses. Communication between the diagnostic system and JBE is independent of these buses, because the diagnostic lead is connected directly on the JBE.

Examples of functions that require both buses and the gateway: DSC button, volume control on the multifunction steering wheel (additional F-CAN)

Examples of functions that require the K-CAN: Power windows passenger's door via switch passenger's door, center lock button, parking-brake switch

Examples of functions that require the PT-CAN: Wiper functions (additional F-CAN), windscreen washing pumps (additional F-CAN)

Line connections in the JBE:
Alongside its electronic function, the JBE also has a connecting function for many cables of the 4 connectors connected to the JBE:
- Internal connector between JBE and distribution box: X04010
- Connector in direction of travel: X14270
- Connector in opposite direction of travel: X14271 and X14272

The connections only serve to optimize the wring harness. The JBE only functions here as a cable. In detail, the following connections are involved:
- 4 power supplies (F58, F59, F60, F61)
- One for activation of the horn relay
- 2 for the outdoor temperature sensor
- 2 for F-CAN
- One for the hotel position switch
- 2 for SMG rocker switch
- 2 for blower (diagnostic signal/ PWM control signal)
- One for the electrical auxiliary heater (PWM control signal)
- One for the center lock button
- 21 ground outputs connected with ground input on X14270
- 5 K-CAN connections CAN-Low (internally connected on one cable)
- 5 K-CAN connections CAN-High (internally connected on one cable)

Functions of the JBE:
The JBE performs the following functions:
- Gateway to diagnostic lead
- Gateway between PT-CAN and K-CAN
- Activation of the bistable relay for cutoff in the case of closed-circuit current faults (same as MPM on E60). The relay is only installed for certain optional extras (e.g. CCC, M-ASK, TCU, ULF). If a bistable relay is installed, an IBS is also installed.
- Power window functions (sensor system (depending on variant): Hall sensors - 2 for passenger's side at rear and 2 for driver's side at rear; switches: passenger's door, passenger's side at rear, driver's side at rear; drives: passenger's side rear, driver's side rear)
- Windscreen washing (contacts: reset contact at front, reset contact at rear; activation: relay for wiper stage 1 and wiper stage 2, rear window wiper relay)
- Central-locking functions (activation of all drives)
- Air-conditioning functions (sensor system (depending on variant): AUC sensor, coolant pressure sensor, rear stratification flap potentiometer; activation (depending on variant: auxiliary water pump, water valve, control valve in the air-conditioning compressor)
- Functions for instrument cluster (sensor system: fuel gauge sensor 1, fuel gauge sensor 2, coolant level, wash water level, parking-brake switch)
- DSC button (switch: DSC button)
- Mirror/washer nozzle heating (activation: washer nozzle heating and basic variant of the mirror heating, together via an internal electronic switch). Activation of mirror heating not if LIN mirrors are installed. Then activation via LIN from FRM.
- Seat heating (activation: PWM signal for basic variant of seat heating, driver's side and passenger's side). Not if seat module is installed on corresponding side. Then activation via seat module of corresponding side.
- Heated rear window (activation: heated rear window relay)
- Headlight-cleaning system (activation: relay for headlight-cleaning system)
- Roller sun blind (activation: drive for roller sun blind)