2001 AUDI A4 sensor

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Advance by technology
The new Audi A4,
a vehicle which combines driving pleasure and good sense
with the highest level of quality and sports styling.
Control unit for vehicle electrical system
...48
New engine programme
...18
Electronic stability programme with
brake assistance
...32
Steering column switch module
...44
Crash sensors for front airbag
...14
Multi-communication bar
...72
Trapezium link
rear axle
...27
Aero-floor
...7

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Important:
Note
New

Contents
It is not intended as a workshop manual.
The self-study programme will provide you with information on
design and functions.
For maintenance and repair operations it is essential that you
refer to the current technical literature.
Page
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Occupant protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Engine and gearbox
Running gear
Axles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Mechanical unit mountings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Brake system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Brake assistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Vehicle electrical system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
CAN BUS system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Dash panel insert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Steering column switch module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
Function circuit diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Control unit for vehicle electrical system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Function circuit diagram for "lowline" version . . . . . . . . . . . . . . . . . . . . . 50
Function circuit diagram for "highline" version . . . . . . . . . . . . . . . . . . . . 52
Convenience system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Anti-theft alarm system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Radio - chorus II, concert II and symphony II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Navigation IV and Navigation Plus-D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Multi-communication bar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Electric logbook "Audi Logbook" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Heater/AC
Design and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
7-piston compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Air conditioner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Glove compartment cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Solar roof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Fresh air blower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Actuators/sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Functional diagram for fully automatic air conditioner . . . . . . . . . . . . . . 84
Additional heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 2.0 l R4 and 3.0 l V6 engines (see SSP 255) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Innovations - 2.5 l V6 TDI engine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Innovations - automatic gearbox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Electrical system

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High safety standards
With a thoroughly optimised body design and
comprehensive safety equipment, the new
Audi A4 is able to comply with all current valid
safety standards, throughout the world.
Crash sensors for the front airbags integrated
directly into the bumper bar, improve occu-
pant protection.
Finely-tuned aerodynamics
Despite the greater frontal area and the cool-
ing air current for the air conditioner (stand-
ard), it was possible to improve the C
D

value
by 5 %, in comparison to its predecessor,
to 0.28.
A special feature is the so-called aero-floor,
which provides for optimal airflow on the
underside of the vehicle.
Communication centre on wheels
With regard to infotainment, the new
Audi A4 leaves nothing to be desired.
4 different audio systems, 2 differently config-
ured Navigation systems and a car phone
with voice operation are on offer.
Electronic stability programme (ESP)
including brake assistant
For the latest ESP generation, the hydraulic
brake assistant is an integral part of the
standard equipment.
It is intended to assist the driver by automati-
cally increasing the brake pressure during
emergency braking.
SSP254_048

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The system comprises driver/passenger air-
bags, front side airbags, optional rear side
airbags, SIDEGUARDS
®

, three point front seat
belts with ball tensioners and belt force limit-
ers, three point rear outer seat belts, centre
lap belt (for fixed rear seat bench), Isofix pre-
paration in rear of vehicle, and a total of 6
non-central accelerometers:
– 2 front impact crash sensors
– 2 driver/passenger side airbag crash sen-
sors, (in the B-pillar for side impact)
– 2 driver/passenger rear side airbag crash
sensors, (on the C-pillar for side impact) To complement the comprehensive body
modifications, occupant protection has been
improved through the further development of
the familiar 8.4 airbag system.
The new generation bears the designa-
tion 8.4 E, where the E stands for
"extended".
The position of the sensors is selected so that
they are installed as near as possible to the
outer structure of the vehicle.
This enables quicker deceleration detection in
the event of an impact.The external sensors deliver digitised acceler-
ation data to the airbag control unit, which is
then evaluated in the control unit and which
triggers the relevant restraint system compo-
nents.
Key
E224 Key switch for switching off
passenger’s side airbag
G179 Side airbag crash sensor, driver’s
side (B-pillar)
G180 Side airbag crash sensor, passenger’s
side (B-pillar)
G256 Crash sensor for rear side airbag,
driver’s side
G257 Crash sensor for rear side airbag,
passenger's side
G283 Front airbag crash sensor, driver’s
side
G284 Front airbag crash sensor,
passenger’s side
J162 Heater control unit
J220 Control unit for motronic
J234 Airbag control unit
J285 Control unit with display unit in
dash panel insert
J393 Central control unit for convenience
system
J526 Control unit for telephone /
telematics
J533 Diagnosis interface for data bus
(Gateway)K75 Airbag warning lamp
K145 "Airbag off" warning lamp,
passenger's side
N95 Airbag igniter, driver's side
N131 Airbag igniter 1, passenger's side
N153 Igniter for belt tensioner, driver's side
N154 Igniter for belt tensioner,
passenger's side
N199 Igniter for side airbag, driver’s side
N200 Igniter for side airbag, passenger's
side
N201 Igniter for rear side airbag,
driver’s side
N202 Igniter for rear side airbag,
passenger's side
N277 Igniter for airbag in B-pillar
(SIDEGUARD

®

), driver's side
N278 Igniter for airbag in B-pillar
(SIDEGUARD
®

), passenger's side
T16 Connector, 16-pin, diagnosis
connection

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Crash sensors for front airbag G283, 284
Both sensors for front impact detection func-
tion in conjunction with the crash sensor and
the safe sensor which are integrated into the
airbag control unit J234.
Deceleration load
Time [ms]
Vehicle rebound Impact
Triggering of belt tensioners
Triggering of front airbags
Front airbags inflated
Belt force limiter
response
Damping function
response in
the steering column

SSP254_063
SSP254_064
Upper body
Head

If a certain signal threshold is exceeded in the
front airbag crash sensor, a threshold reduc-
tion is activated in the airbag control unit,
which results in a shorter triggering time.
Occupant protection
SSP254_058

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Re-encoding of the airbag control unit is no
longer possible after the first crash data mes-
sage is stored.
Triggering is performed in two thresholds
depending upon the deceleration value:
– Threshold 1 = belt tensioners only
– Threshold 2 = belt tensioners and airbag(s)
Crash sensors for side airbags
G179, 180, 256, 257
In order to trigger the components of the
restraint system, two simultaneous impact
detection signals are required for the plausi-
bility check:
– from both opposing crash sensors
(B-pillar left with right and/or
(C-pillar left with right) and
– from the control unit internal crash sen-
sors.
The crash sensors are designed in such a way
that incorrect installation is excluded.
Airbag control unit J234
The warning lamp for airbag K75 is activated
continuously following a detected impact.
"CRASH DATA STORED" and the triggered
components are displayed with fault code
during fault memory readout.
Sensors and components to be replaced
following an accident, are listed in the
current workshop manual.
SSP254_059

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Brake assistant
Investigations in accident research have
shown, that the majority of drivers fail to ade-
quately actuate the brakes in an emergency
situation.
This results in insufficient brake pressure
being generated to achieve maximum vehicle
deceleration.
This lengthens the braking distance.During emergency braking, the brake assist-
ant aids the driver by increasing the brake
pressure automatically, to a level exceeding
the locking limit.
The ABS (
A
nti-lock
b
raking
s
ystem) is thus
quickly brought into the operating range,
which enables a maximum vehicle decelera-
tion to be achieved.
Brake servo pressure sensor G294 is used for
detection of emergency braking.
Time [t]
Pressure [p]

For this purpose, the pressure increase gradi-
ent (pressure build-up with respect to time) is
evaluated and, if necessary, the brake assist-
ant is activated.
SSP254_093
Emergency braking
Normal braking distance
Pressure sensor G294

Running gear
SSP254_092

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Front airbag crash sen-
sor, driver’s side G283

Vehicle electrical system
Electrical system
Control unit for
coolant fan,
Stage 1+2 J293Control unit
for ESP J104 Control unit for
telematics J499
Control unit for
mobile phone control
electronics J412
Front airbag crash
sensor, passen-
ger’s side G284
Control unit
for Motronic J220
Control unit for auto-
matic gearbox J217
Control unit for headlamp
range control J431Chip card
reader R99
Steering column
switch module J527
Battery
Control unit with
display in dash panel
insert J285