2001 AUDI A4 brake 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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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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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)