Onboard power supply management
Switching off convenience electrical equipment
With the ignition on or active alternator (engine running), the onboard power supply control is classified
by the onboard power supply control unit as very critical if the voltage of the onboard power supply
battery is below 12.2 volts for a certain period dependent on the electrical equipment.
The result is that convenience electrical equipment is switched off by priority by its control unit.
If an item of electrical equipment is not switched on, it is skipped and the next item is switched off.
Drive Train CAN bus Convenience CAN bus
Gateway
Engine Signals for Onboard
control unit switching off power supply
electrical control unit
equipment
Rise in idling speed
Battery voltage
2nd stage
Control units involved in switching off electrical equipment
Control unit for Central control unit Control unit for Door control unit, Control unit for Onboard power
air conditioning for convenience steering column driver's side seat adjustment supply control unit
system system electronics - Driver
- Front passenger S272_015
- Rear compartment
28
If the state of the onboard power supply remains very critical after the convenience electrical equipment
has been switched off, a second stage of the idle speed increase is initiated.
If this does not improve the state of the onboard power supply, the air conditioning system is also
switched off.
Switch-off sequence
Reduction in heat
output to 50%
PTC to 25% * Mirror heating off Steering wheel Reduction in air
Seat heater and
heating switch-off conditioning
ventilation off
system
Switch-off Wiper park PTC off * Rear window
PTC to 75% * PTC to 50% * windscreen position heater off heater off
Electrical equipment switch-off
* PTC heating element in the rear footwell flaps
S272_084
29
State of the onboard power supply
Networked functions
Networking system
On today's vehicles, activation and supply of the lighting system can no longer be implemented via
conventional switches, relays and cable connections. Networked functions in these vehicles handle the
corresponding functions.
Schematic diagram with control units
involved in lighting control system and networking as an example
Turn indicators
Dipped beam headlights
Turn indicator in the mirror
Main beam headlights
Courtesy light
Parking light
Door exit light
Rotary door
Fog lights
latch
Door handle lighting, interior
J234
Airbag control
J386
Interior lighting
unit
Door control unit,
front passenger
Reading lights
J217
Control unit for
Convenience lighting
gearbox
Switch for convenience
lighting
J285
J518 Control unit
Switch for
Dash panel insert
for entry and
reading lights
gateway
start authorisation
Switch for
Direction of travel
interior lights
J528
Control unit for
sunroof
electronics
Brake light switch
J523 Control unit
J519 J527 Control unit
for front
onboard power for steering
information display
supply control column
and operating unit
unit electronics
Light switch
J387
Turn indicator switch
Door control unit,
Hazard warning light switch
driver
Switch for manual
dipping and flasher
Dimming +
Fog lights
Dimming -
Turn indicator in the mirror
Rotary door
Parking light
Front footwell lighting latch Courtesy lights
Main beam headlights
Door exit light
Dipped beam headlights
Door handle lighting, interior
Turn indicators
30
Activation signals are sent to control units via resistance-coded switches, and these either activate the
electrical equipment themselves or send the activation signal via a databus system to the control unit in
charge of activation. The supply of the electrical equipment is then via the control unit in charge.
Turn indicators Indicator lights
Brake light Brake light
Door exit light
Tail light Tail light
Rotary door latch
Door handle lighting
Rear fog light Rear fog light
Reversing light Reversing light
J389
Rear right door
control unit
Rear footwell lighting
Rotary door latch, boot
J521 Control unit J393 Central
for front control unit for
passenger's seat convenience
adjustment system
boot light
Courtesy lighting (rear)
Number plate lights
Number plate lights
3rd brake light
J136 Control unit J345 Control unit
for driver's seat for trailer
adjustment detection
J388
Rear footwell lighting
Rear left door
control unit
Reversing light Reversing light
Rear fog light Rear fog light
Tail light Tail light
Rotary door latch
Door exit light
Brake light Brake light
Door handle lighting
S272_087
Turn indicators Turn indicators
31
Networked functions
By way of illustration, the CAN lines
Brake light control
(orange) for the signals are represented
individually. In reality, all the signals are
Control units involved
sent via a CAN High and a CAN Low
Central control unit for convenience system
line.
Control unit for trailer detection (optional)
Dash panel insert
Brake light switch
Dash panel insert
Central control Control unit for
optional
unit for trailer detection
convenience
system
Brake light, left Brake light, right Brake light, left Brake light, right
S272_062
Brake light, top centre
Signals
1 Activation of the central control unit for the 4 Fault message from control unit for trailer
convenience system and the control unit for detection to the dash panel insert via
trailer detection viathe brake light switch with Convenience CAN bus; if the brake light is
an analogue voltage defective,
a fault message appears in the display
2 Power current to the brake light from central
control unit for convenience system or control 5 Safety signal. If the activation signal from the
unit for trailer detection brake light switch to the control unit for trailer
detection is missing, information is provided
3 Fault message from central control unit for
through the central control unit for
convenience system to the dash panel insert
convenience system
via Convenience CAN bus; if the brake light is
defective, a fault message appears in the
display
32
Control of side lights and tail lights
Control units involved
Onboard power supply control unit
Central control unit for convenience system
Control unit for trailer detection (optional)
Dash panel insert
Light switch
Front left side light
Onboard power
Front right side light
supply control
unit
Left side light
Dash panel insert
Right side light
Central control Control unit for
optional
unit for trailer detection
convenience
system
Left tail light Right tail light Left tail light Right tail light
Number plate lights Number plate lights
S272_045
Signals
1 Activation of the onboard power supply 5 Fault message to the dash panel insert via
control unit by the light switch with an Convenience CAN bus; if a tail light is
analogue voltage defective,
a fault message appears in the display
2 Activation signal from the onboard power
supply control unit to the central control unit 6 Fault message to the dash panel insert via
for convenience system and control unit for Convenience CAN bus; if a tail light in the
trailer detection via Convenience CAN bus trailer is defective, a fault message appears in
the display
3 Power current to the side lights and tail lights
4 Fault message to the dash panel insert via
Convenience CAN bus; if a side light is
defective, a fault message appears in the
display
33
Networked functions
Light activation via the light switch or the automatic driving light control
Control units involved
Onboard power supply control unit
Dash panel insert
Control unit for entry and start authorisation
Control unit for sunroof electronics
Light sensor
Control unit for
sunroof
Light switch
electronics
Control unit for
entry and start
authorisation
Onboard power
Dipped beam headlight, left
supply control unit
Dipped beam headlight, right
S272_048
Dash panel insert
Signals If light sensor fitted
1 Signal 'Ignition on' from control unit for entry 4 Analogue brightness signal from light sensor
and start authorisation via Convenience CAN to control unit for sunroof electronics
bus
5 Signal 'Switch on dipped beam headlights' via
2 Activation of the onboard power supply Convenience CAN bus in the case of
control unit by the light switch with an automatic driving light control from control
analogue voltage signal, Vbat approx. 12 unit for sunroof electronics to onboard power
volts supply control unit
3 Power current to the headlights 6 Fault message to the dash panel insert via
Convenience CAN bus; if dipped beam
headlight is defective, a fault message
appears in the display
34
Control of the turn indicator
Control units involved
Onboard power supply control unit
Turn indicator switch
Control unit for entry and start authorisation
Control unit for steering column electronics
Dash panel insert
Control unit for Control unit for
steering column entry and start
Driver's door control unit
electronics authorisation
Front passenger's door control unit
Control unit for trailer detection (optional)
Turn indicator,
front left
Turn indicator,
Onboard power
front right
supply control unit
Turn indicator,
rear left
Turn indicator,
Dash panel insert
rear right
optional
Door control unit, Door control unit, Control unit for
driver front passenger trailer detection
Side Side
indicator, indicator,
left right
(mirror) (mirror)
Left turn indicator Right turn indicator
S272_047
Signals
1 Signal 'Ignition on' from control unit for entry 6 Signal for activation of the indicator lamps
and start authorisation via Convenience CAN and poss. fault messages via Convenience
bus CAN bus from onboard power supply control
unit to dash panel insert
2 Signal 'turn indicating' from turn indicator
switch into control unit for steering column 7 Signal for activation of the indicator lamps
electronics and poss. fault messages via Convenience
CAN bus from control unit for trailer detection
3 Signal 'turn indicating' from control unit for
to dash panel insert
steering column electronics via Convenience
CAN bus to onboard power supply control
unit
4 Power current to the indicator lights
5 Signal 'turn indicating' from onboard power
supply control unit via Convenience CAN bus
to door control units driver/front passenger
and, if present, to the control unit for trailer
detection
35
Networked functions
Hazard warning lights control
Control units involved
Onboard power supply control unit
Dash panel insert
Driver's door control unit
Front passenger's door control unit
Control unit for trailer detection (optional)
Hazard warning lights button
Turn indicator,
front left
Onboard power
Turn indicator,
supply control unit
front right
Turn indicator,
rear left
Dash panel insert
Turn indicator,
rear right
optional
Door control unit, Door control unit, Control unit for
driver front passenger trailer detection
Side Side
indicator, indicator,
left right
(mirror) (mirror)
Turn indicators
S272_088
Signals
1 Signal 'hazard warning lights' from hazard 4 Signal for activation of indicator lamps and
warning lights button to onboard power acoustic check signal and poss. fault
supply control unit messages via Convenience CAN bus from
onboard power supply control unit to dash
2 Signal 'hazard warning lights' from onboard
panel insert
power supply control unit via Convenience
CAN bus to door control units driver/front 5 Signal for activation of the indicator lamps
passenger and, if present, to the control unit and poss. fault messages via Convenience
for trailer detection CAN bus from control unit for trailer detection
to dash panel insert
3 Power current to the indicator lights
36
Control of the rear window heater
Control units involved
Control unit, front information display and
operating unit
Onboard power supply control
Button for
unit
rear window heater
Onboard power
Central control unit for
supply control unit
convenience system
Control unit for
Central control
front information
unit for
display and
convenience
operating unit
system
Relay for
heater field 1
Relay for
heater field 2
Rear window
S272_049
Signals
1 Signal from rear window heater button to 5 Signal 'Power output reduction of rear window
control unit, front information display and heater' via Convenience CAN bus from
operating unit onboard power supply control unit to central
control unit for convenience system
2 Signal 'Button actuated' from control unit,
front information display and operating unit
to central control unit for convenience system
via Convenience CAN bus
3 Analogue activation of the relay for heater
The upper and lower heater fields of
field 1 and 2 on rear window
the rear window are activated
4 Signal 'Heater fields of rear window switched
separately. In the case of an overload
on' via Convenience CAN bus from central
of the onboard power supply control
control unit for convenience system to
unit, the onboard power supply control
onboard power supply control unit and
unit reduces the heat output by 50%.
control unit for front display and operating
The heater fields are activated
unit;
alternately.
indicator lamp is switched on
37
Networked functions
Control of windscreen heater
The windscreen heater is switched on by
the control unit for air conditioning
Control units involved
system depending on the ambient
temperature. The switch-on time is
Control unit, front information display and
based on the ambient temperature:
operating unit
+5 to 0°C = 2 minutes
Onboard power supply control unit
0 to -20°C = 4 minutes
Control unit for air conditioning system
-20 to -40°C = 6 minutes
Dash panel insert
Activation via the defrost button is only possible
when the engine is running, when the ambient
temperature is colder than +5°C, and there is no
Button
engine load limitation.
Defrost
Onboard power
supply control unit
Control unit for
Dash panel insert
front information
display and
operating unit
Control unit for Control unit for
air conditioning windscreen heater
system
Windscreen heater
S272_050
Signals
1 Signal 'Windscreen heater on' with 5 Signal 'Windscreen heater on' from control
manual operation unit for air conditioning system to dash panel
insert as well as information signal
2 Forwarding of signal 'Windscreen heater on'
'Windscreen heater on' from control unit for
in the case of manual operation from control
air conditioning system to onboard power
unit for front display and operating unit for
supply control unit via Convenience CAN bus
information to control unit for air conditioning
system via Convenience CAN bus 6 Activation to control unit for windscreen
heater to switch on the windscreen heater
3 Signal 'Engine speed > 0 rpm' from dash
panel insert to control unit for air conditioning
system via Convenience CAN bus
4 Signal 'Switch-off windscreen heater' in the
case of load limitation from onboard power
supply control unit via Convenience CAN bus
38
Control unit for windscreen heating
P
In order to enhance convenience and safety
(fogged or iced windows), a heated windscreen
is used.
1000 W
The windscreen is heated by means of an
integrated metal foil. Due to the necessary
electrical power output of approx. 1000 watts, as
a result of the foil resistance, a voltage is
required that exceeds the onboard power supply
voltage of 12 volts.
100 W
U
This voltage is provided by the control unit for the
windscreen heater (DC/DC converter).
12.2 V 12.7 V 13.1 V
Depending on the input voltage, an output
Input voltage
S272_089
S272_089
voltage of up to 42 volts DC and power output of
up to 1000 watts is provided.
A crack in the windscreen or a short circuit is
detected by the control unit. The windscreen is
then not heated.
The control unit for the windscreen heater is
located in the rear right of the boot.
S272_094
Control unit for
windscreen heater Starter battery
39
Output voltage
Switches
Resistance-coded switches
Switches serve to switch electrical components
and functions on and off.
In the case of conventional switches, one cable
connection per switch function is required.
Resistance-coded switches need a considerably
lower number of cable connections.
Functional example
Switch for steering wheel adjustment
Switch open
Switch for steering
If all the switches are open, no signal is
wheel adjustment
transmitted to the steering column module.
Steering
column
module
down up back forward
S272_064
Switch for steering
Switch 'down' is actuated
wheel adjustment
Via contact A2, the steering column module
transmits a voltage signal to the switch. This
voltage signal is changed by resistance R4. As
the resistances R1, R2, R3 and R4 are different,
the control unit recognises the switch position.
Steering
column
module
down up back forward
S272_065
40
Dash panel
1 2 3 4 5 6 7 8 9/10
S272_026
11 12 13 14 3
1 Fog light, optional 9 Turn off parking aid
2 Rotary light switch 10 Rear roller blind up/down
3 Vent flow restrictor 11 Turn indicators and main beam headlights
4 Rear fog light 12 Steering wheel adjustment
5 Instrument lighting 13 Wipers
6 Reset trip recorder 14 Electronic ignition lock
7 Tiptronic -
8 Tiptronic +
41
Switches
1 2 3 4 5 6 7 8 9
Front information display and operating unit
1 Air conditioning temperature, driver's side
2 Automatic air conditioning, driver's side
3 Windscreen defrost
4 Air conditioning toggle Quattro/Mono
5 Hazard warning light switch
10
10
6 Air conditioning air recirculation
7 Rear window heater
8 Automatic air conditioning, front passenger's side
9 Air conditioning temperature, front passenger's
side
11
11
10 Softkeys for menu control
13
11 Switch-over menu on screen
12 Radio operating keys
13 Rotary/push knob
12
S272_039
Multi-function steering wheel 8
9
7
1 APC or CCS On/Off
10
2 APC Distance +/- 6
11
3 APC or CCS Cancel
5
12
4 Key lighting On/Off (on the back)
4
5 APC or CCS -
13
3
6 APC or CCS Set
14
2
7 APC or CCS Resume
15
8 APC or CCS +
1
9 Volume +
S272_027
10 Answer telephone call
11 Navigation announcement
12 Volume -
13 Menu selection, forward
14 List selection
15 Menu selection, backward
Driver's door
1
1 Locking/unlocking doors
(in driver's and front passenger's door)
S272_031
42
Driver's door
1
1 Defroster vent, driver's door
2 Bootlid open
2
3 Tank filler flap release
4 Front right window regulator
5 Right child-proof lock
3
9
6 Rear right window regulator
8
7 Rear left window regulator
4
8 Left child-proof lock
7
9 Front left window regulator
5
6
S272_030
Centre console
1 Deactivation, front passenger's airbag 1
2 Indicator lamp, deactivation front passenger's
2
airbag
3 Seat heater and ventilation, front passenger
9
(optional)
4 Damper setting
5 ESP switch
8
6 Air suspension adjustment
7 Seat heater and ventilation, driver, and
steering wheel heating (optional)
7 6 5 4 3
8 Mirror adjustment, mirror heating,
optional mirror folding function
S272_038
9 Ignition and starting engine, optional
12 3
Driver's and front passenger's seat
1 4-way adjustment lumbar support
4
2 Belt height adjustment
3 Position memory of seats
(3 positions, 1 set)
4 Seat adjustment
5 Massage On/Off
5
S272_029
43
Switches
Rear roof module
1 Rear left reading light On/Off
2 Interior light via door contact On/Off
3 Interior light On/Off
4 Rear right reading light On/Off
12 34
S272_037
12
Front roof module
1 Trigger for programmed remote control
( e.g. open garage door)
2 Interior light On/Off
3 Reading light On/Off
4 Control of sliding/tilting roof
3 3
5 Hands-free microphone for driver
(car phone and voice operation)
4
6
6 Interior light via door contact On/Off
S272_036
5
44
Operating elements on the console in the rear
1 Vent flow restriction, centre rear right
2 Switch-over to seat control, front passenger's seat
3 Rear right seat setting
4 Rear right seat heater and ventilation
5 Rear right seat memory
(2/3 positions and massage at 2 positions)
1
6 Rear left seat memory
(2/3 positions and massage at 2 positions)
2
7 Rear left seat heater and ventilation
8 Rear left seat setting
3
9 Vent flow restriction, centre rear left
4
98 7 6 5
S272_032
12
Rear air conditioner/Climatronic operating 1
and display unit (four-seater)
2
11
1 Rear right head vent 3
2 Rear right body vent
10
3 Rear right foot vent
4
4 Rear right manual temperature control
5 Rear right automatic control 9
6 Fan +/-
7 Rear left automatic control
5
8 Rear left manual temperature control
9 Rear left foot vent
8 7 6
10 Rear left body vent
S272_033
11 Rear left head vent
12 Display
As regards operation of a retrofitted
version, please consult the manual.
1
Rear doors
1 Locking/unlocking doors
New!
S272_035
45
Dash panel insert
The dash panel insert is designed as a premium
version with a 5" colour TFT screen (thin-film
transistor) and a highline version with a 3"
monochrome dot-matrix screen.
S272_056
S272_056
The top-of-the-range dash panel insert has the
following functions:
Analogue displays 5" colour TFT screen
Speed (country-specific in kph, mph + kph, The on-board computer can be switched to
kph + mph) country-specific units
Engine speed Driving time
Fuel gauge Distance
Coolant temperature Average speed
(country-specific in °C/°F) Average consumption
Oil temperature (country-specific in °C/°F) Momentary consumption
Onboard power supply voltage (V) Ambient temperature/ice warning
Odometer display Remaining distance
(total distance driven, trip counter) Maintenance due indicator
Gear selection for automatic
Alarm indications with pictograms
Navigation/radio data
APC displays
Tyre pressure warning
Lamp failure display
Highline dash panel insert
a 3" monochrome dot-matrix screen
a clock with LC display in the rev counter
a total distance driven and trip counter with
LC display in the speedometer
46
1 2 3 4
Layout of the display
1 Audio part display
Warnings
2 Multi-function display
Warnings
160 km/h
160 km/h
160 km/h
160 km/h
Automatic proximity control main screen
5
P
P
P
P
Voice input
R
R
R
R
Navigation main screen
Car phone
N
N
N
N
Telematics
D3
D3
D3
D3
Audio
160
160
160
160
S
S
S
S
3 Buttons of the multi-function steering wheel
9
that can be activated
APC part screen
o
o
o
o
412.3km 12.3C 123456km
412.3km 12.3C 123456km
412.3km 12.3C 123456km
412.3km 12.3C 123456km
Audio list
Car phone list
8 7 6
Navigation: current road
S272_082
Warnings
4 Marker for warnings
5 Gear selection display
6 Total distance driven
7 Ambient temperature
8 Trip counter
9 Red symbol for APC
The display areas 1, 2 and 3 are assigned
according to the priority of the displays
to be shown.
High, red warnings:
Danger or cars down
Medium, amber warnings:
Messages
Low:
Information
47
Dash panel insert
Existing driver information
Driver information Analogue display Symbols Text messages
ABS
APC displays e.g. APC defective
Airbag displays e.g. airbag fault
o
o
o
o
12.3C
12.3C
12.3C
12.3C
Ambient temperature
Onboard power supply voltage Electrics: electrical
equipment switch-off
Lack of brake fluid e.g. brake fluid, stop
vehicle!
Brake fault, EBD fault e.g. brake fault, stop
vehicle!
Brake wear Check brake pads
Damper function e.g. Sport
Damper fault Fault
Oil pressure, engine off!
Dynamic oil warning
Engine speed
EPC
Ice warning
ESP/TCS displays
Turn indicator check, trailer
Turn indicator check, left/right
Main beam headlights
Handbrake Release handbrake!
123456km
123456km
123456km
123456km
Total distance driven
Speed
Light bulb failure e.g. check rear fog
light
Light bulb failure, brake light Please check brake
light
ID sender 'Battery warning' Key battery empty
ID sender not authorised Key not authorised
(immobiliser)
ID sender not detected e.g. system fault,
workshop!
Fuel gauge
Lack of coolant Lack of coolant
Coolant temperature
Coolant overheating Coolant overheating
48
Driver information Analogue display Symbols Text messages
Charge control Alternator, workshop
Please move steering wheel
Steering wheel cannot be locked
Steering wheel locked Locking: press start/
stop for longer period
Steering defective Steering defective,
workshop
Headlight range control failure Check headlight range
control
Light warning e.g. switch on side
lights
Bonnet, doors, bootlid open, child-
proof lock
Fog lights
Rear fog light
Self-levelling function e.g. vehicle lowering
Level, fault Fault
Emergency start Please start engine
EOBD e.g. engine fault
Oil temperature
Oil level too low Check oil level
Oil level sensor defective Oil sensor fault,
workshop!
e.g. tyre pressure control off
Tyre pressure control displays
Key warning Key not found
Shift lock Press brake
Seat belt, driver Driver: fasten seat belt
123.4km
123.4km
123.4km
123.4km
Trip counter
Fuel warning Please refuel
D3
Gear selection display D3
D3
D3
Place selector lever in position 'P' Place selector lever in
position 'P'
Service due indicators e.g. Service now
Washer fluid level Add washer fluid
49
Networking
Databus topology
The databus system has been expanded to a
great extent. It has three subsystems, the
- Drive Train CAN bus,
- Convenience CAN bus,
- Infotainment CAN bus.
G259 J217 J343
Sender for Control unit for Control unit for
proximity control autom. gearbox gas discharge
headlight, left
J539 J367 J344 J519
Control unit for Control unit for Control unit for Onboard power
brake servo battery monitoring gas discharge supply control unit
unit headlight, right
Lateral accel. +
J584
yaw rate
Control unit for
J104 J197 J400
wiper motor, front
ABS with ESP Self-levelling Control unit for
passenger's side
control unit suspension control wiper motor
unit
Turbocharger 2
Interior monitor;
Control unit for J518
J528
Only V10 TDi rain sensor/
turbocharger Control unit for
Control unit for
light sensor;
entry and
sunroof electronics
sliding/tilting roof
start authorisation
Multi-function
steering wheel
J399 J527 J301
Only V6 TDi
Control unit Control unit for Control unit for
for injection steering column air conditioning
pump electronics system
J624 J234
Engine control Airbag control unit
unit -2-
J526
Control unit for car
phone / telematics
J623 J285
Engine control unit Dash panel insert
(Gateway)
50
Mir Receive
Engine CU slave on W12 and
V10 TDi
Diagnosis via the databus
CAN bus
Gateway
The diagnosis via the communications line only
Drive Train CAN
Communications
takes place now in the case of a few control units bus
line
in the Drive Train CAN bus subsystem, the gas
Convenience
Virtual
discharge headlights and in the central control
CAN bus
communications line
unit for the convenience system.
Infotainment
Optical databus
CAN bus
*J657 * Slave
Control unit
J389
for power
Rear right door
latching
control unit
All other control units, except for the
analogue clock, the control units for
*
turbochargers 1 and 2, the injection
J522
J345 J388 pump and the control unit for trailer
Control unit for rear
Control unit for Rear left door
detection have a virtual communications
seat adjustment with
trailer detection control unit
line. Diagnosis is performed via the bus
memory
system. The control units send their
diagnostic data via the gateway in the
*
dash panel insert to the diagnostic
J521
J446 J387 testing and information system. In the
Control unit for front
Control unit for Door control unit,
case of a defective dash panel insert, no
passenger's seat
parking aid front passenger's adjustment with
diagnosis of control units is possible
memory
side
using the virtual communications line.
*
J136
J502 J386
Control unit for
Control unit for Door control unit,
driver's seat
tyre pressure driver's side adjustment with
memory
monitoring
J605
Control unit for
The control unit for trailer
E265 Rear operating J393
tailgate
and display unit for
Central control unit
angle sensor
detection as well as the
air conditioning
for convenience
system
analogue clock do not have
system
self-diagnostic capability.
J401 J523 R 41 J524 J525
Navigation control Control unit, front CD changer Control unit, rear Control unit for
unit with CD drive information display information display digital sound
and operating unit and operating unit package
Optical databus
R 78 J167
Y
TV tuner Control unit for
Analogue clock
additional heating
S272_057
51
If J523_H fitted, no air conditioner operating unit and vice versa!
Networking
The control units in the Drive Train
CAN bus
The Drive Train CAN bus operates at a data If one of these lines is defective, has a short
transfer rate of 500 kbit/s. The data is circuit or an interruption, data transfer is no
transmitted via the CAN High and CAN Low line. longer possible or only to a limited extent.
J623
J367 J197
Engine control unit
Control unit for Self-levelling
J624
battery monitoring suspension control unit
Engine control unit -2-
J539
Control unit for brake servo unit
J217
Control unit
for autom. gearbox
J527
Control unit for steering
column electronics
J285
Dash panel insert (Gateway)
J518
Control unit for entry and
start authorisation
J234
G259
Airbag control unit
J104
Sender for
ABS with ESP control unit
proximity control
S272_076
52
Linking the Drive Train CAN bus
The control units are networked using a combination of linear and star-shaped links.
G259
Sender for
proximity control
J104 J624
J217 J623
ABS with ESP Engine control
Control unit for Engine control unit
control unit unit -2-
autom. gearbox
J539
Control unit for
brake servo unit
J285
Dash panel insert
(Gateway)
J234
Airbag control unit
J527
Control unit for
steering column
electronics
J518
Control unit for
entry and
start authorisation
J197 J367
Self-levelling Control unit for
suspension control battery monitoring
unit
S272_058
53
Networking
Control units in the Convenience
CAN bus
The Convenience CAN bus operates at a data Various control units are designed as masters
transfer rate of 100 kbit/s. and communicate with their slaves via an
internal data line to which only they have access.
Data is transmitted via the CAN High and CAN Slaves are executing control units that run the
Low line. instructions from their master, e.g. switching on
the wiper motor.
If one of these lines is defective, has a short
circuit or an interruption, data transfer is possible
only via one line.The databus goes to single-wire
mode.
J393
J605
Central control unit for
Control unit for tailgate
convenience system
J528
J446
Control unit for sunroof
Control unit for parking aid
E265
electronics
Rear operating and display unit
for air conditioning system
J345
Control unit for
J387
trailer detection
Door control unit, front
J389
passenger's side
Rear right door control unit
J523
Control unit, front information
display and operating unit
J519
Onboard power supply control
unit
J502 - Control unit for
tyre pressure monitoring
J388
Rear left door control unit
J386
Door control unit, driver's side
J527
Control unit for steering
column electronics
J285
Dash panel insert (Gateway)
J400 J301 J518
Control unit for wiper motor Control unit for Control unit for entry and start
air conditioning system authorisation
S272_074
54
Linking the Convenience CAN bus
The control units are networked using a combination of linear and star-shaped links.
J527 J285 J528 J301
Control unit for Dash panel insert Control unit for Control unit for air
steering column (Gateway) sunroof conditioning
electronics electronics system
J387
Door control unit,
front passenger's
J386 J400
side
Door control unit, Control unit for
driver's side wiper motor
J523 - Control unit
for front
information display
J518
and operating unit
Control unit for
entry and start
J519
authorisation
Control unit for
onboard power
supply
J388 J389
E265 Rear operating
Rear left door Rear right door
and display unit for
control unit control unit air conditioning
system
J521
Control unit for front
passenger's seat
adjustment with
memory
J524
J136
Control unit, rear
Control unit for driver's
information display
seat adjustment with
and operating unit
memory
J522
J502
Control unit for rear
Control unit for
seat adjustment with
tyre pressure
memory
monitoring
J345
J393 J446
Control unit for
Central control unit Control unit for
trailer detection
for convenience parking aid
system
S272_059
55
Networking
Control units in the Infotainment
CAN bus
The Infotainment CAN bus operates at a data The front and rear control units, information
transfer rate of 100 kbit/s. display and operating units as well as the
navigation control unit communicate with one
The data is transmitted via the CAN High another via an optical bus to which only they
and CAN Low line. have access.
If one of these lines is defective, has a short
circuit or an interruption, data transfer is possible
only via one line.The databus goes to single-wire
mode.
J526
Control unit for car
J523 Y
phone / telematics
Control unit, front information Analogue clock
R78
display and operating unit
TV tuner
J401
Navigation control unit with
CD drive
R41
CD changer
J525
Control unit for
digital sound package
J524
Control unit, rear
information display and
operating unit
J285
Dash panel insert
(Gateway)
J167
Control unit for
S272_075
auxiliary heating
56
Linking the Infotainment CAN bus
The control units are networked using a combination of linear and star-shaped links.
J167
Control unit for
auxiliary heating
Y J401
Analogue clock Navigation control
unit with
CD drive
J285 J523 Control unit,
front information
Dash panel insert
display and
(Gateway)
operating unit
Optical bus
J524 Control unit,
rear information
display and
operating unit
J525
R 78
Control unit for
TV tuner
digital sound
package
J526
Control unit for
car phone/
telematics
S272_060
57
Networking
Optical databus
The front control unit, information display and
J401
Navigation control unit with CD drive
operating unit as well as the navigation
computer communicate with one another via an
optical bus to which only they have access.
Optical
The optical databus operates at a data transfer data line
rate of 11.2 Mbit/s.
The available bandwidth is suitable for
transmitting data from the navigation CD-ROM.
On the connection level, this optical bus system is
based on a single polymer fibre-optic cable that
connects all the devices in a ring topology.
The information is received via an optical
receiving diode and is forwarded via a
transmitting diode.
J523
Control unit, front information display
and operating unit
Due to the ring-shaped design, overall failure of
S272_091
the databus is unavoidable if one node is unable
to pass on the information.
Receiving diode
J401 J523
When laying fibre-optic cables, special
Transmitting diode
care is necessary, as it is only possible
to bend them up a maximum radius of
25 mm.
Receiving diode
J524
S272_090
58
Gateway
The gateway control unit is integrated in the dash
panel insert as software; it controls
communication traffic over the bus systems
- Drive Train,
- Convenience and
- Infotainment
Drive Train CAN bus Convenience CAN bus
500 kbit/s 100 kbit/s
Dash panel insert
Engine control unit Gateway Onboard power supply
control unit
Infotainment
CAN bus
100 kbit/s
Control unit, front information
display and operating unit
S272_066
59
Analogue clock
The high-quality analogue clock is integrated in
the wood trim strip of the dash panel in the
vehicle centre.
The time is set using the control unit for the front
information display and operating unit. The
signals are transmitted via the CAN bus.
In the case of vehicles with navigation system, the
time is synchronised by the Global Positioning
System (GPS) via the navigation computer.
Dash panel insert
Analogue clock
Gateway
Navigation control unit
with CD drive
Control unit, front information
display and operating unit
S272_067
60
Glossary
CAN bus Polymer fibre-optic cable
A large number of control units are required in This lead comprises fibre-optic cable,
today's motor vehicles. In order to implement comparable with flexible Plexiglas, through
their functions, data interchange among them is which digital light signals can be transmitted for
absolutely necessary. The conventional method data transfer without loss. Fibre-optic cables are
of interchanging information via individual cable a modern transfer medium, operating on an
connections has reached its limits. The CAN bus optical basis. The data is transported by means
connects the control units with two bi-directional of high-frequency light pulses.
data lines. Data transfer is digital.
TFT screen
Dot-matrix screen
Thin Film Transistor screen, technology used for
Numbers, letter and characters are shown flat monitors; provides good contrast and a clear
on the screen as interrelated dots. picture.
Electrical equipment required for starting
Electrical equipment absolutely necessary for
starting:
Engine control unit
Fuel pump
Electronic ignition lock
Dash panel insert
Control unit for entry and start authorisation
Airbag control unit
Global Positioning System
This navigation system developed by the US
Ministry of Defense makes world-wide
navigation possible. With currently 24 to 27
satellites, the accuracy of position determination
is ideally under 10 m.
61
Test your knowledge
1. What are the power management components?
a) The starter battery, the onboard power supply control unit, the relay for parallel switching of
batteries, the switch-over relay for starter battery, the switch-over relay for onboard power supply
and the onboard power supply battery
b) The starter battery, the control unit for battery monitoring, the relay for parallel switching of
batteries, the switch-over relay for starter battery, the switch-over relay for onboard power supply
battery and the onboard power supply battery
c) The starter battery, the control unit for battery monitoring, the relay for parallel switching, the
switch-over relay for starter battery, the main relay and the onboard power supply battery
2. Which statement is correct?
a) In the case of vehicles with petrol engine and two-battery onboard power supply, both batteries
are connected in series at temperatures below -20°.
b) In the case of vehicles with petrol engine and two-battery onboard power supply, both batteries
are switched in parallel at temperatures below +5°.
c) In the case of vehicles with petrol engine and two-battery onboard power supply, both batteries
are switched in parallel at temperatures below -10°.
3. What functions are switched through the onboard power supply control unit?
a) Parking lights, main beam headlights, central locking, dipped beam headlights
b) Fog lights, side lights, indicator lights, footwell lights
c) Horn, indicator lamp for hazard warning lights, relay for headlight washer system
62
4. Which statement is correct with regard to switching off convenience electrical equipment in the
case of a very critical onboard power supply?
a) Convenience electrical equipment is switched off by priority.
b) Convenience electrical equipment is switched off depending on the amount of power consumption.
c) Convenience electrical equipment is switched off in the order they were switched on.
5. Which control units are involved in turn indicator activation?
a) The steering column switching module, the control unit for entry and start authorisation, the
onboard power supply control unit, the door control unit on the driver's and front passenger's side
a) The steering column switching module, the control unit for entry and start authorisation, the
indicator relay, the door control unit on the driver's and front passenger's side
a) The control unit for entry and start authorisation, the onboard power supply control unit, the door
control unit on the driver's and front passenger's side, the control unit for trailer detection
6. Which control units belong to the Convenience CAN bus?
a) The gas discharge headlights, the control unit for entry and start authorisation, the control unit for
sunroof electronics, the control unit for the air conditioning system
b) The onboard power supply control unit, the control unit for battery monitoring, the control unit for
the additional heating
c) The control unit for trailer detection, the door control unit, the control unit for air conditioning
system, the seat memory control units
63
c; 4a; 5a; 6c
.
Solution: 1b; 2c; 3b u
272
For internal use only. © VOLKSWAGEN AG, Wolfsburg
All rights reserved. Technical specifications subject to change without notice.
240.2810.91.20 Technical status: 03/02
This paper is produced from
non-chlorine-bleached pulp.