General Electrical System - Service Techniques (E88): Other BMW 1 series F20/F21

System functions

The following system functions for the digital compass are described

1. Display
2. Brightness control of display
3. Adjustment of magnetic field zones and calibration
4. from 09/2006: Further adjustments
5. up to 09/2006: Fault display Display The 8 points of the compass are digitally displayed by abbreviations. from 09/2006 The display is available in English and German (delivery status: English LHD) N: North NE: North East Nordosten E: East Osten SE: South East Sudosten S: South SW: South West W: West NW: North West The changeover between displays is carried out as follows: The current vehicle position is the center of a 360° circle. The eight points of the compass divide these 360° into sixteen 22.5° segments. The display changes over if the direction of travel changes by more than 22.5°.

Brightness control of display

1. 2 photodiodes in the electrochromic interior mirror record the surrounding brightness (1 photodiode for the surrounding brightness coming from the front, 1 photodiode for the surrounding brightness coming from the rear).

The photodiodes deliver the signals for the display brightness control.

The brightness of the display is adjusted by the interior mirror control electronics to suit the surrounding brightness.

1. E88, E93

A darkened interior mirror will become lighter while the soft top or the retractable hardtop is opening and closing.

The overhead control panel (FZD) transmits the signal (roof open or closed) to the control electronics for the interior mirror. The signal is transmitted on the wire that is also used for transmitting the signal for driving in reverse.

Preconditions for activation

At terminal 15 ON, the display is activated with a test run.

1. up to 09/2006

During this process, the LC matrix lights up completely (approx. 3 seconds). The digital compass is then switched on. There is no switch for turning off the LCD display at terminal 15 ON.

Scheme 565

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

1. 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.
2. 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
3. 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
4. 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

1. Selective unlocking
2. Deadlock release
3. Locking
4. Unlocking and deadlock release
5. Deadlocking

The boot lid lock is activated via its own output stage.

1. 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)
2. 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.
3. 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).
4. 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.
5. 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
6. 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.
7. DTC button The junction box electronics unit detects signals from the DTC button.
8. Parking brake warning switch The junction box electronics unit detects signals from the parking brake warning switch.
9. Roller sunblind for rear window The junction box electronics actuates the drive for the roller sunblind.
10. Servotronic valve

On vehicles with Servotronic, the junction box electronics actuates the Servotronic valve (only on vehicles without option 217 "Active Steering").

Cable connector

As well as its electronic function, the junction box electronics unit (JBE) also has a connector function. Many of the wires from the 4 connectors that are connected to the junction box electronics are linked via the junction box electronics. The connections optimize the wiring harness. Here, the junction box electronics work as a node.

Junction box electronics relays

The junction box electronics unit (JBE) has internal and external relays. The excitation coils on all relays are permanently supplied with a positive cable. The positive power supply for the external relays is provided via the load circuit which is to be switched through. The positive power supply for the internal relay is provided via the fused junction box electronics supply wire. 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 circuit. All other external relays on the junction box electronics are located upstream of the fuse on the current circuit.

The internal relays are

1. Relay for power window drive, rear
2. Relay for central-locking drive (except tailgate)

The external relays are

1. Relay for drive, rear window wiper
2. Relay for drives, wiper stage 1 and wiper stage 2
3. Relay for headlight washer system
4. Relay for heated rear window
5. Bistable relay (deactivation of closed-circuit current fault)

Notes for service staff

Service staff should note the following points

1. General information
2. Diagnosis
3. Encoding/programming

Subject to change.

Scheme 566

The following system functions of the power supply system are described

1. Power management with engine running: "Basic Power Management" functions with standard equipment and "Advanced Power Management" with High equipment level
2. Emergency operation in the event of bitserial data interface failure
3. Energy management even when engine is not running: Power supply for control units, consumer cutoff of auxiliary consumers and off-load current monitoring
4. Data transfer for power supply Power management The power management system is the most important component of the energy management system. The power management system is a software package in the engine control unit (DME or DDE). When the engine is running, the power management system regulates the alternator voltage. Depending on the vehicle's equipment, there are 2 versions of the power management: Basic Power Management (BPM) on vehicles with standard equipment and only a few items of special equipment Basic Power Management controls the idle speed. Basic Power Management also specifies the charge voltage according to demand. Advanced Power Management (APM) on vehicles with High equipment level, e.g. with the following items of special equipment: CCC: Car Communication Computer M-ASK: Multi-audio system controller BMW "Professional" radio in US version Telephone in US version. Advanced Power Management is only available with the intelligent battery sensor. Advanced Power Management gives precise consideration to the current battery condition: The intelligent battery sensor reads the corresponding data. When the engine is running, the power management system regulates the following: Alternator voltage regulation When the engine is running, the alternator generates a variable voltage, the alternator voltage. This variable alternator voltage is regulated by the power management according to the following criteria: Nominal value for alternator voltage: The respective nominal value for alternator voltage depends on how many electrical consumers are switched on. Battery temperature: To prevent the battery from overheating, the optimum charge voltage is regulated. The alternator voltage is regulated by the engine control unit (DME or DDE). The alternator should always deliver as much current as the electrical consumers need. The engine control unit adapts the alternator voltage as follows, depending on the consumers in use: By increasing engine speed By increasing excitation current to alternator coils The data is exchanged via the bitserial data interface. Battery charging regulation On vehicles without intelligent battery sensor, the battery temperature (for example) is calculated. On vehicles with intelligent battery sensor, the battery condition is recorded precisely by the intelligent battery sensor. Load-dependent reduction of some consumers Only on vehicles with High equipment level and intelligent battery sensor On vehicles with intelligent battery sensor, consumers may be reduced or even switched off altogether, even if the engine is running. This consumer cutoff reduces current consumption in critical situations. This ensures that the battery is not discharged. The affected consumers are either switched off completely of their power output is reduced. On vehicles with diesel engine, the power consumption of the electric auxiliary heater is regulated.

Emergency operation in the event of bitserial data interface failure

If the bitserial data interface between the engine control unit and the alternator is interrupted, the alternator voltage will be regulated to a constant 14.3 V.

Energy management system

The energy management system is software package in several control units, e.g.

1. CAS: Car Access System
2. JBE: Junction Box Electronics
3. Engine control unit: DME or DDE).

The energy management system monitors and regulates the power supply, even when the engine is not running.

1. Power supply for control units To ensure that the vehicle retains its starting capability, there are two additional terminals for permanent current (terminal 30): Terminal 30g (active) Terminal 30g-f (cutoff in case of fault, only on vehicles with High equipment level). These new terminals allow consumers to be cut off and off-load current to be monitored when the vehicle is our of use.
2. Auxiliary consumer cutoff Terminal 30g (terminal 30 active): Terminal 30g means "active continuous positive": Components with power supply via terminal 30g are switched off according to time. The Car Access System (CAS) uses terminal 30g as follows to effect a time-controlled cutoff of control units and components with power supply: Approximately 30 minutes after terminal R is switched OFF, the power supply for these components is switched off. This prevents the battery from being subjected to excess load by the electrical consumers for too long when the vehicle is out of use.
3. Control unit cutoff in case of fault Cutoff in case of fault is only available on vehicles with High equipment level (e.g. on vehicles with CCC or M-ASK).

Cutoff in case of fault helps to maintain the vehicle's ability to start.

All control units and components on terminal 30g-f are cut off if any of the following faults develop

1. Control units frequently woken up after terminal R is switched OFF: Some control units do not "go to sleep", but rather remain active.
2. Prolonged undervoltage on bus systems
3. Data buses do not go to "sleep" after terminal R is switched OFF.

Data transfer for power supply

The CAS (Car Access System) forwards the data for the terminal control as follows

1. Terminal R ON or OFF
2. Terminal 15 ON or OFF
3. etc.

The CAS switches the corresponding relays for the following terminals

1. Terminal 15
2. Terminal 30g

The junction box electronics switch the corresponding relay for the following terminal

1. Terminal 30 g-f

The control units on these terminals are supplied with power and "woken up".

The corresponding vehicle systems are activated.

The consumers are primarily supplied via terminal 30g and terminal 30g-f (only on vehicles with High equipment level).

However, certain consumers are also supplied directly from terminal 30.

For example, the anti-theft alarm must also be active when the ignition is switched off.