light AUDI A4 2001 B5 / 1.G Technical Features Design And Function

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5 V/Div.=10 ms/Div.
0 T

Electrical system
In the "highline" version of the vehicle electri-
cal system control unit, only the 21 watt
filament of the two-phase bulb for the brake
and rear light is used.
With lights switched on and non-actuated
brakes, the power rating is reduced to 5 watts
by a pulse-width modulated signal via the
vehicle electrical system control unit J519.
Thus a self-diagnosis/driver information
system (FIS) is possible for the second rear
light.
A defective brake light would be indicated in
FIS.
In vehicles with the "highline" version, national
lighting regulations can be adapted via
coding.For non-plausible condition of the rotary
light control, the side lights and low beam
are switched on automatically by the vehi-
cle electrical system control unit in the
"highline" version.
SSP254_080
Measuring equipment
DSORecorder operation

Photo
Channel A
Channel B
Measuring
mode
Cursor 1
Cursor 2
Multimeter
Help Print
PositionTime/Div.
Trigger mode
Skip

Brake not actuatedBrake actuated
Rear lights on:
5 V/Div.=2 s/Div.
0

Electrical fault finding
In certain lighting circuits, an open-circuit
voltage measurement using the Multimeter is
not possible, as the semi-conductor elements
are clocked until the circuit is again closed.
For defective bulbs which are operated via the
vehicle electrical system control unit J519, no
permanent fault storage is effected, but only
for the period of the fault.
This means that the fault memory must not
be erased after changing a defective bulb.
Measuring equipment
DSORecorder operation

Photo
Channel A
Channel B
Measuring
mode
Cursor 1
Cursor 2
Multimeter
Help Print Ve h i c l e
self-diagnosis
Position Time/Div.

Reversing lamp on:
1 - bulb illuminates
2 - bulb failure
3 - clock frequency of power output
1
2
3
SSP254_052

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55
The hazard warning flasher signal is control-
led separately by the vehicle electrical system
control unit, via the hazard warning flasher
button.
If, during hazard warning flashing, the turn
signal flasher is actuated, e.g. during towing,
the hazard warning lights lose their priority
for this period.
The turn signal clicking is generated by an
integral acoustic relay in the dash panel
insert.
Turn signal/hazard warning light control
The functions:
– Anti-theft alarm flasher
– Central locking system flasher when
opening/closing
– Key-learn flasher for key adaption
– Crash flasher
– Panic flasher (USA only)
are specified by the central convenience elec-
tronics and transmitted via the convenience
data bus to the vehicle electrical system con-
trol unit, which then executes the "com-
mands".
The signal for turn signal flashing or motor-
way flashing is output via the steering column
switch module and executed by the vehicle
electrical system control unit.
For active hazard warning flasher with
ignition OFF, the flasher bulbs are actu-
ated for a shorter period in order to mini-
mise current consumption.
Motorway flashing is detected by the vehicle
electrical system control unit when the turn
signal lever is pressed and this triggers a tri-
ple turn signal flash.

Turn signal light, right
Turn signal light, left
Turn signal light, right
Turn signal light, left
SSP254_077
SSP254_078

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Electrical system
The windscreen wash/wipe relays are inte-
grated into the vehicle electrical system
control unit J519.
The washer fluid reservoir is a two-part
design for easier removal and installation.
An additional sensor is fitted for vehicles with
headlight washer system (HWS). In the
"highline" version, this is also used for the
Check system.
The purpose of the sensor, is to switch off the
HWS pump via the vehicle electrical system
control unit.
This prevents the pump running dry.
Wash/wipe system
The wash/wipe system is equipped with the
speed-dependent 4-stage interval system.
A new feature is the re-wipe function for the
windscreen washer system.
Re-wiping occurs automatically 5 seconds
after the wash procedure is completed.
Headlight washer sys-
tem pump V11
Windscreen and
rear screen washer
pump V58
Windscreen washer fluid
level sender G33 Reservoir in engine
compartment
Reservoir in front left
wheel housing
Connected

SSP254_024

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Control unit for trailer recognition J345
A separate control unit is required for trailer
operation. This transmits the vehicle lighting
system convenience CAN messages from the
vehicle electrical system control unit to the
trailer lights. A parallel link from the trailer
socket to the vehicle wiring would result in
fault detection via the microprocessor in the
vehicle electrical system control unit.
The diagnostic function of the control unit for
trailer recognition is performed via the
vehicle electrical system control unit J519,
address word 09.
In the case of faulty communication
between the control unit for trailer recog-
nition and the vehicle electrical system
control unit, the rear lights are actuated
as a warning signal.
RT

Address word 09 - vehicle electrical system/
Central convenience
electronics
Communication takes place by means of the
convenience data bus via the central conven-
ience electronics, as no separate K-wire
leads to the vehicle electrical system control
unit. For this reason, intact central conven-
ience electronics are essential for perform-
ing self-diagnosis.
K wireCAN
BUS
Central convenience
electronics J393
SSP254_018J389
J388J387
J386
Door control units
Control unit for vehicle
electrical system J519
Control unit for trailer
recognition J345
09 – Electronic central electrics
8E0907279B
int. load module RDW 0811
Code 101
Dealership No. 6803
02 - Interrogate fault memory
03 - Final control diagnosis
04 - Basic setting
05 - Erase fault memory
06 - End output
07 - Encoding control unit
08 - Read measured value block
09 - Read individual measured value
10 - Adaption
11 - Log-in procedure

Measuring
equipmentSkip PrintHelp
Steering column
switch module J527
Vehicle self-diagnosis

Steering wheel
electronics
module J453
SSP254_016
VAS 5051

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In the basic version without rear electric win-
dow lifters, central locking control of the rear
doors is assumed by the central convenience
electronics.
Convenience system
The convenience system previously used in
the Audi A2 is also used in the Audi A4.
In the series version, the following additional
functions
– Door warning lights
– Radio remote control
and in the optional version, the following
functions
– Anti-theft alarm with interior monitor and
towing protection (new)
– Electric sliding/tilting/glass sun roof
– Footwell lights
– Exit lights
– Mirror fold-in function
– Mirror memory function
are included in the Audi A4.
Electrical system
Central convenience unit J393
Door control unit,
passenger’s side J387 Door control,
driver’s side unit
J386
Door control unit,
rear right J389
(optional) Door control unit,
rear left J388
(optional)
SSP254_132

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The following information and functions
are processed in the central convenience
electronics:
Crash signal
(from airbag control unit J234)
Handbrake switch F9
Tailgate release
– Button for release, tailgate lock
cylinder F248
– 3. Remote control button
– Switch for tailgate to F206
– Switch for central locking, tail-
gate F218
Anti-theft alarm (optional)
– Contact switch for bonnet F266
– Ultrasonic sensor for anti-theft
alarm G209
Aerial for remote control,
Central locking and anti-theft
alarm in multi-communication bar
Reversing lamp M17
When mechanical window lifters
fitted in rear
– Door contact signal
– Locking signal
– Safe signal
for rear doors
Fuel filler flap
– Motor for tank cap locking V155
Tailgate
– Motor for tailgate release V139
Anti-theft alarm (optional)
– Horn for anti-theft alarm H8
(sounder)
– Turn signal lights via data bus to
vehicle electrical system con-
trol unit J519
Interior light control
– Dimming of interior lighting
– Footwell light switching
(optional)
– Luggage compartment lamp
switching
Automatic closing/opening
– Window lifters via door control
units
– Sun roof
When mechanical window lifters
fitted in rear
– Lock rear door lock motors
– Safe rear door lock motors
– Activation of rear entry lights
(optional)
– Activation of rear door warning
lights
Enabling of door control units and
sunroof
Gateway function for diagnosis
– Control unit for vehicle electrical
system J519
– Steering column switch module
J527
Sensors Actuators Central convenience electronics (CCE)

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Door control units
The door control units integrated in the
window lifter motors process the following
signals:
Window lifter switches
Enabling via the CCE
Door lock feedback signal
– Door contact signal
– Locked signal
– Safe signal
for driver’s door also
– Lock cylinder switch unlocking/
locking F241
– Interior central locking switch
F59
– Switch for childproof lock E254
(optional)
– Central window lifter operation
– Mirror adjustment switching E48
– Switch for mirror adjustment E43
– Switch for mirror fold-in function
(optional) E263
– Switch for unlocking luggage
compartment (USA) E164
– Switch for seat memory, driver’s
side (optional) E263
– Switch for interior monitor E183
(optional)
– Inclination sensor switch
(optional)
for front doors also
– Mirror release switch (optional)
– Sender for mirror position for
mirror memory (optional)
Door locking and unlocking
Safe activation and deactivation of
the doors
Activation of illumination in the
doors
– Entry lights (optional)
– Door opener illumination
(optional)
– Door warning lights
– Switch illumination
for front doors also
– Electric mirror adjustment
– Mirror heating
– Mirror fold-in function
– Mirror memory
for driver’s door also
– Control of indicator LED
– Inclination sensor LED switched
off (optional)
– LED, interior monitoring
– LED, childproof lock
additionally for passenger's door
– Mirror for reversing (optional)
Sensors Actuators
Electrical system

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Heater/AC
Significant advantages in comparison with
vehicles without solar roof are:
– lowered temperature level in vehicles
parked in the sun (see chart),
– increased efficiency of the air conditioner
as the interior temperature set is achieved
more quickly,
– despite the reduced output of the system
during the winter, an air-drying effect
occurs which effectively dehumidifies the
vehicle, reducing fogging of the windows.
Solar roof
For the first time, the A4 can optionally be
equipped with the solar roof previously used
in the A8 and A6.
The fresh air blower is continually driven by
electricity obtained from solar radiation.
The output is proportional to the intensity of
the sunlight.
Modifications to the familiar models:
– Re-engineered fresh air blower
– The DC/DC transformer has been discontin-
ued, its function is now performed by the
fresh air blower control unit J126.
Time [min]
Temperature [°C]
Radiation [W/m

2

]
Ventilation
Air conditioner
with control
systemSolar generator
SSP254_035
SSP254_036

Contacts
Heating without solar
Heating with solar
Global radiation

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Actuators/sensors
Heater/AC
Ambient temperature sensor
G17
Dash panel temperature
sensor G56
and
Temperature selection in the air condi-
tioner operating and display unit E87
Sender for footwell vent temperature,
right, G262
Sender for footwell vent tempera-
ture, left, G261
High-pressure sender G65 Evaporator outlet temperature
sender G263 Fresh air intake temperature
sensor G89
Sunlight penetration photo-
sensor G107
Signals:
Terminal 31b from automatic wash/wipe interval system
Regulating valve for air conditioner compressor N280
Air quality sensor G238 Vent temperature sender, right, G151
Vent temperature sender, left, G150
E
C
O
NO
F
F

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Heater/AC
Functional diagram
for fully automatic air
conditioner
Components
C20 Solar cells
E87 Operating and display unit for
air conditioner
G59 Driver’s seat temperature sensor
G60 Front passenger’s seat temperature
sensor
G65 High-pressure sender
G89 Temperature sensor - fresh air intake-
channel
G107 Sunlight penetration photosensor
G112 Potentiometer in positioning motor
for central flap
G113 Potentiometer in positioning motor
for air flow flap
G135 Potentiometer in central flap control
motor defrost flap
G143 Potentiometer in central flap control
motor recirculated-air flap
G150 Vent temperature sender, left
G151 Vent temperature sender, right
G220 Potentiometer, positioning motor for
temperature flap, left
G221 Potentiometer, positioning motor for
temperature flap, right
G238 Air quality sensor
G262 Vent temperature sender, footwell,
left
G262 Vent temperature sender, footwell,
right
G263 Vent temperature sender, evaporator
J9 Relay for heated windscreen and
rear window
J126 Blower control unit
N280 Regulating valve for compressor,
air conditioner
S Fuses
V2 Fresh air blower
V70 Central flap control motor
V71 Air flow flap control motor
V107 Defrost flap control motor
V113 Air recirculation flap control motor
V158 Temperature flap positioning motor,
left
V159 Temperature flap positioning motor,
right
1
2
3
4CAN-high convenience
CAN-low convenience
Terminal 75
Windscreen heating Z2
K-diagnostic connection
CAN-H CONVENIENCE
CAN-L CONVENIENCEConnection to
convenience data
bus
Colour coding
= Input signal
= Output signal
= Positive power supply
= Earth
= CAN-BUS

Auxiliary signals
Z1 Heated rear window
Z6 Heated driver’s seat
Z8 Heated front passenger’s seat
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