Power Supply
61 01 05 (125)
Power supply
E65, E66
Introduction
The power supply is regulated principally by the power module. Amongst other things, the power module monitors the battery charge state and the vehicle's off-load current consumption.
The following modifications to the power module are to be introduced in March 2005 with the Model Year measures:
- Modified hardware and software
- CAS and DME connected to terminal 30LM
(CAS = Car Access System; DME = digital engine electronics; LM = light module)
Note: Power supply to digital diesel electronics via power distributor.
Power is still provided to the digital diesel electronics (DDE) via the fuse box in the engine compartment.
Until now, the power module only cut current from the current paths terminal 30B and terminal 30U in the event of an off-load current violation.
This meant that an off-load current violation could only be detected using the current at terminals 30U and 30B.
A new feature is that terminal 30LM is now also switched by the power module. However, current measurement is not possible at terminal 30LM. Increased off-load current consumption is indirectly detected by the monitoring of bus communications on the K-CAN. (K-CAN = "body controller area network.)
Brief description of components
Various components and control units are involved in the power supply system.
- PM: Power module
When the vehicle is at rest, the power module will switch most consumers off if the battery voltage drops too far. This ensures the vehicle can still be started.
Amongst other things, the power module switches the following terminals:
- Terminal 30B
Terminal 30B connects the front power distributor with the power module.
- Terminal 30LM
The following control units are connected to terminal 30LM:
- Car Access System (CAS)
- Digital engine electronics (DME)
- Light module
- Instrument cluster
- Remote control receiver
- Terminal 30U
Terminal 30U connects the rear power distributor with the power module.
- Terminal for "consumer shutdown, rear roof"
- Terminal for "consumer shutdown, front roof"
- Terminal for "consumer shutdown, interior lighting"
- Terminal for "consumer shutdown, body"
- Fuse box
Power is provided to the digital diesel electronics (DDE) via the fuse box in the engine compartment.
- Front power distributor
The front power distributor is connected to the power module via terminal 30B.
- Rear power distributor
The rear power distributor is connected to the power module via terminal 30U.
- DME or DDE: Digital engine electronics or digital diesel electronics
The DME or DDE is connected to the alternator via the local CAN. The DME or DDE receives the following messages from the power module: Calculated temperature and charge level of battery. The DME or DDE regulates the output of the alternator. This enhances the battery's charge balance.
- Alternator
When the engine is running, the alternator generates a variable charge voltage for battery charging. The variable charge voltage is monitored by the power module. The charge voltage is adapted by increasing the engine speed or excitation current. The DME or DDE regulates the charge voltage.
- LM: Light module
The light module regulates the exterior lighting on the vehicle (e.g. side lights and hazard warning lights).
- CAS: Car Access System
The CAS monitors the state of the central locking system. The CAS controls the terminal switching and issues the start enable signal via the ignition-starter switch with integrated electronic immobilizer.
- Remote control receiver
The remote control receiver is connected to terminal 30LM. A radio signal is emitted when the button on the radio remote control or the Telestart transmitter is pressed. Signal path: Radio remote control -> Rear-window aerial -> Remote control receiver -> CAS
- DWA: Anti-theft alarm system
The anti-theft alarm system is permanently connected to terminal 30 via the power module.
During "terminal 30LM reset", the vehicle can only be mechanically opened using the integrated key element. When terminal 30LM is reactivated, the DWA will trigger the alarm.
Reason: When terminal 30LM is reactivated, the door modules transmit their current state. The alarm is triggered because the state has changed (door opened).
- KOMBI: Instrument cluster
The charge-current indicator light is located in the instrument cluster.
- Battery
The battery charge state is monitored by the power module.
- Battery switch
The battery switch has 2 positions: ON and OFF.
In the ON position, the power module is in off-load current monitoring mode.
In the OFF position, the power module goes into transport mode after 30 minutes. Some of the comfort functions cannot be used in transport mode (e.g. radio or television). Current consumption is thus reduced.
- Battery positive support point
The battery positive support point in the engine compartment is extension of the positive terminal of the battery to an easily accessible point. A battery charger can be connected either to the battery positive support point or directly to the battery.
- Battery cable
The battery cable is split up as follows:
- 1 wire to the power module
The power module is directly connected to the battery.
- 1 wire to the safety battery terminal
The battery is connected to the following components by the safety battery terminal:
- Starter motor
- Alternator
- Battery positive support point
- Fuse box
- Safety battery terminal
Depending on the severity of the accident, the safety battery terminal disconnects the starter motor and the alternator from the battery. This minimizes the risk of short circuits in a serious accident. A triggering signal comes from the right-hand B-pillar satellite.
- SBSR: B-pillar satellite, right
The SBSR records the severity of an accident using acceleration sensors. If certain operating thresholds are exceeded, the safety battery terminal is triggered.
- SGM: Safety and gateway module
The SGM is the data interface between the K-CAN and the PT-CAN. (K-CAN = "body controller area network"; PT-CAN = "powertrain controller area network".)
System functions
The following system functions of the power supply system are described:
- Consumer shutdown
- Off-load current violation detection
- Shutdown on excessive off-load current
- Shutdown on excessively frequent wake-up
- Battery starting capability retention
- Reduced run-down period
Consumer shutdown
To prevent the battery from being discharged due to continuous operation of consumers, the terminals to the consumers are shut down.
The CAN bus goes into standby a few minutes after terminal R is switched OFF. After 16 minutes, the power module transmits a signal for consumers to be shut down. When this happens, the CAN bus is briefly reactivated.
The following terminals are switched off:
- Terminal for "consumer shutdown, rear roof"
- Terminal for "consumer shutdown, front roof"
- Terminal for "consumer shutdown, interior lighting"
- Vehicles without telephone:
Terminal for "consumer shutdown, body"
- Vehicles with telephone:
After 60 minutes (can be encoded), the terminal for "consumer shutdown, body" is switched off.
The output for the telephone drawer is connected to the terminal for "consumer shutdown, body".
The power module starts the monitoring off-load current.
If certain consumers are switched on, off-load current monitoring will not be active.
These consumers are needed for the following reasons:
- Legally stipulated consumers
(e.g. side lights, hazard warning lights)
- Occupant comfort
(radio, telephone)
Off-load current violation detection
During off-load current monitoring, the power module measures as follows:
- Voltage measurement every 5 seconds
- Current measurement every 60 seconds An off-load current violation is detected if more than 80 milliamperes are measured.
If the power module detects an off-load current violation, a special off-load current monitoring function starts, as follows: The power module measures the instantaneous current value every 1.5 seconds for 8 minutes.
This gives the vehicle electrical system a period of time to restore normal off-load current.
If a current less than 80 milliamperes is detected for longer than 1 minute during the special off-load current monitoring, the special off-load current monitoring is restarted.
If the off-load current violation is still present after the special off-load current monitoring, the power module will send a warning to all control unit on terminals 30B, 30U, 30LM: These terminals are switched off: The power module issues the warning in the form of a message to the connected control units.
Shutdown on excessive off-load current
The shutdown message tells all control units: The connection to the battery will be switched off in 90 seconds.
This enables all control units with memory function to store their data in their non-volatile memory.
After 90 seconds, the control units are shut down.
The shutdown is performed as follows:
1. Terminals 30B and 30U briefly shut down by power module (as previously):
All consumers on terminals 30B and 30U are isolated from the battery (for 30 seconds).
Off-load current is then monitored for 8 minutes.
2. Terminals 30B and 30U permanently shut down by power module (as previously):
If the off-load current violation is maintained, the shutdown message is issued again (for 90 seconds).
All consumers on terminals 30B and 30U are isolated from the battery again.
3. New: Terminal 30LM briefly isolated from power module
After terminals 30B and 30U have been shut down, the bus participants on the K-CAN must go into standby within an encoded period of time (e.g. 5 minutes).
If not, the power module will isolate terminal 30LM from the vehicle electrical system for an encoded period of time (e.g. 10 seconds).
After this, a terminal 30LM reset will be started. This reset will effect a reset of all control units connected to terminal 30LM.
Current measurement is not possible at terminal 30LM. The power module will detect an increased off-load current consumption indirectly by monitoring bus communications on the K-CAN.
Terminal 30LM is only separated when terminal 30B and terminal 30U are already permanently separated.
The "terminal 30LM reset" process will only be performed once within a special off-load current monitoring period. Reason: During this process, all control units on terminal 30LM are actuated. This results in increased current consumption.
The "terminal 30LM reset" function and the specified value for shutdown times can be encoded.
Note: No loss of data in instrument cluster during "terminal 30LM reset".
The brief shutdown of the power supply does not cause a loss of data in the instrument cluster.
Only the clock will be retarded by the time involved (approx. 10 seconds).
Note: Not possible to unlock vehicle with radio remote control during "terminal 30LM reset".
The vehicle cannot be unlocked with the radio remote control during the "terminal 30LM reset".
Reason: During "terminal 30LM reset", neither the remote control receiver nor the CAS (Car Access System) are supplied with power.
The vehicle can be mechanically unlocked using the integrated key element. When terminal 30LM is reactivated, the DWA will trigger the alarm.
Reason: When terminal 30LM is reactivated, the door modules transmit their current state. The alarm is triggered because the state has changed (door opened).
Shutdown on excessively frequent wake-up
If the vehicle is "woken" excessively frequently after terminal R has been switched OFF, the power module will isolate the vehicle electrical system from the battery. The number of wake-up processes can be encoded. At present, 30 wake-up processes are encoded. The wake-up could be caused by operation of the controls or by a defective component (e.g. control unit).
The shutdown is performed as follows:
1. Terminals 30B and 30U shut down by power module
When the encoded number of wake-up processes is reached, terminals 30B and 30U are shut down by the power module.
2. Terminal 30LM briefly shut down by power module
After terminals 30B and 30U have been shut down, the bus participants on the K-CAN must go into standby within an encoded period of time (e.g. 5 minutes).
If not, the power module will isolate terminal 30LM from the vehicle electrical system for an encoded period of time (e.g. 10 seconds).
A terminal 30LM reset is started. All control units connected are set to the basic setting.
Note: Wake-up counter not cleared during "terminal 30LM reset" process.
The wake-up counter is no longer cleared during the "terminal 30LM reset" process (with the previous software, the counter was cleared when the connection between the consumers and the battery was restored).
Battery starting capability retention
Old:
On a vehicle without off-load current violation, terminals 30B and 30U are not separated. This means that the battery capacity could drop below its limit of starting capability without apparent reason and without the power module reacting.
New:
From terminal R OFF, the system will wait for an encoded time (e.g. 5 minutes) if auxiliary consumers are shut down.
If the battery's limit of starting capability is exceeded, terminals 30B and 30U are separated. A "terminal 30LM reset" is performed for an encoded period of time (e.g. 10 seconds).
Exception: The message "starting capability at risk" has already been transmitted on terminal R ON. In such cases, the shutdown is interrupted by a terminal change after terminal R is switched OFF. The shutdown is restarted after a set period of time.
Reason: The occupants are still in the vehicle (terminal R ON). The radio etc. are switched on. Current consumption is high. The power module reacts immediately and reports the low charge with a Check-Control message.
When terminal R is switched off, the control units will not be separated from the battery by the power module for some time. This allows the occupants to leave and lock the vehicle.
Reason: If the control units were to be separated from the power supply too quickly, the door modules would also receive no current. It would no longer be possible to lock the vehicle.
Reduced run-down period
Old:
A vehicle is separated from terminals 30B and 30U due to an off-load current violation. A "terminal 30LM reset" was performed.
The terminals are reactivated (e.g. when the vehicle is unlocked with the radio remote control). The terminals cannot be separated again for 60 minutes (16 minutes without telephone).
This long run-down period could allow the battery charge to drop well below its starting capability limit.
New:
The run-down period for all consumers prior to off-load current monitoring being restarted is set with an encoded value (e.g. 20 minutes).
Note: Reduced run-down period reset after "engine running" signal.
If the power module receives the signal "engine running", the encoded value for the reduced run-down period is reset (20 minutes are encoded).
Notes for service staff
Service staff should note the following points:
- General information:
- Diagnosis: ---
- Encoding/programming: ---
- Car and Key Memory: ---
Subject to change.