2003 AUDI A8 Body control

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Attention
NoteNew
Contents
Page
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Passenger Protection
System layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Safety systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Engine, Mechanics
Technical data of V8 4.2 l 5V engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Technical data of V8 3.7 l 5V engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
System layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Electrohydraulic torque reaction support . . . . . . . . . . . . . . . . . . . . . . . . . 32
Exhaust system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Fuel tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Automatically controlled starting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Gearbox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Running Gear
Front axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Rear axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4-level air suspension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
System layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Electric parking brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Adaptive cruise control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Electrical System
Bus topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Convenience and security electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Lighting system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Heating/Air Conditioner
Design and operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Operating principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Blower unit/air routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
System layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Block diagram for front air conditioner . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Block diagram for rear air conditioner . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
The Self Study Programme contains information on design
features and functions.
The Self Study Programme is not intended as a Workshop
Manual. Values given are only intended to help explain the
subject matter and relate to the software version applicable at
the time of SSP compilation.
Use should always be made of the latest technical publications
when performing maintenance and repair work.

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Introduction
The new Audi A8 is designed to replace its
predecessor of the same name which achieved
a total production figure of 105,092 since its
introduction in June 1994. This was the first
standard saloon with aluminium body and
epitomised a new philosophy in the luxury
vehicle sector.
The weight-saving Audi Space Frame ASF
represented a major breakthrough in terms of
enhanced vehicle dynamics, whilst at the same
time solving the problem of increasing weight.
Introduction
This body concept was further perfected in
the Audi A2 and the design of the Audi A8 ´03
reflects the experience gained from both
projects.
The aim when developing the Audi A8 ´03 was
not merely to surpass its predecessor in
terms of technical features and details.
Convenience/infotainment control
via multimedia interface (MMI)
3.7 or 4.2 l V8 engine
with intake manifold
changeover function
Adaptive cruise control (ACC)
with radar sensor
in front bumper
Headlight with adaptive
light functionActive head restraints
for front seats

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Body
A standard feature is an automatic closing
aid, which is actuated by a Bowden cable
separately from the catch. After the latch has
closed, a mechanism pulls the catch
downwards, overcoming the build-up of
pressure occurring. On locking, a microswitch
in the boot lid lock transmits a signal to the
control unit to activate the automatic closing
aid.
SSP282_035
The drive unit is only encased in foam and
inserted between side panel and battery. Boot lid
Electronic boot lid lock
with microswitch Foam encasing
Motor for automatic
closing aidCatch Bowden
cable

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Body
Front doors
The doors are made up of a combination of
aluminium panels, aluminium sections and
aluminium castings.
Optimised rib geometry and wall thickness in
the hinge and lock mounting castings formed
the basis for ideal implementation of the
lightweight construction concept.
Rear doors
Large, high-strength side impact members
are integrated into the door to provide even
load distribution in the event of side impact.
SSP282_039
Door shell and door frame are connected at
the door pre-assembly stage by means of
fitted bolts to ensure the accurate
assignment of both components. Window
lifter frame, window lifter motor/gear
mechanism, door control unit and speaker
are pre-assembled on a base plate and bolted
to the door subframe.

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4-level air suspension
The introduction of the Audi A8 ´03 is
accompanied by a system featuring new
technical details and functions. The major
differences with respect to the familiar Audi
allroad quattro
® system are as follows:
EDC instead of PDC damping
The control system makes allowance for the
currently applicable driving status. Wheel
movement (unsprung masses) and body
movement (sprung masses) are detected.
Various damping characteristic curves are
implemented within the scope of three
selectable programs (modes) and each
damper can be controlled individually.
Control concept
Integration into the MMI makes for
convenient, logical and easy to remember
control action.
Extended range of sensors
Use is made of three acceleration sensors to
detect body movement.
External air springs
The air spring not only replaces the steel
spring, it also offers major advantages (refer
to SSP 242). The new external routing of the
air spring through an aluminium cylinder
permits the use of thinner-walled bellows.
This results in an even more sensitive
response to road surface irregularities.
SSP282_052
SSP282_053
Optimal comfort and road safety are thus
always guaranteed whichever mode is set
(comfort or sports).
The term "mode" thus describes a
coordinated combination of adaptive
suspension program and damping map.