Audi A8 2002 User Manual

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282

Service.

AUDI A8 ´03 - Technical Features

For internal use only

Self Study Programme 282

Complete vehicle information

The design and operation of the Audi A8 ´03 are described in the following Self Study Programmes:

SSP 283 – 6-speed automatic gearbox 09E in the Audi A8 '03 - Part 1 SSP 284 – 6-speed automatic gearbox 09E in the Audi A8 '03 - Part 2 SSP 285 – Running gear in the Audi A8 '03 SSP 286 – New data bus systems - LIN, MOST, Bluetooth SSP 287 – Audi A8 '03 - Electrical components SSP 288 – Audi A8 '03 - Distributed functions SSP 289 – Adaptive cruise control in the Audi A8 '03 SSP 292 – Adaptive air suspension in the Audi A8 '03 SSP 293 – Audi A8 '03 - Infotainment

Other helpful information on the Audi A8 ´03 can be found on the adjacent CD ROMs.

Electrical system CAN data bus 2

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.

New

Attention Note

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.

Convenience/infotainment control via multimedia interface (MMI)

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.

Active head restraints for front seats

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 function

As the Audi ﬂagship, the new Audi A8 is intended to symbolise the product identity of the next Audi generation.

An uncompromising sporty character, clearcut design, innovative technological systems and the highest possible quality level combine to provide an unforgettable driving experience.

In other words:

Automatic boot lid opening and closing function (optional)

Audi at its proverbial best.

LED-type tail lights

4-level air suspension

6-speed automatic gearbox 09E

Electric parking brake

"Advanced Key" entry and start authorisation system

SSP282_025

Body

Brief outline

976

1444

1629

1894

125

971 2944

5051

1615

2028

714

1136

SSP282_026

Kerb weight 1,780 kg Gross weight 2,380 kg

Turning circle 12 m Luggage compartment volume approx. 500 l

Tank capacity approx. 90 litres Drag coefﬁcient 0.27 C

Body

The Audi A8 ´03 sets new standards in its class by combining lightweight construction with outstanding stability. This is achieved through the use of innovative Audi Space Frame technology for the body design of the Audi A8. The technical progress reﬂected by the unique body concept stems from the consistent implementation of experience gained from the aluminium Audi A8 and A2 models.

Based on the ﬁndings obtained from these vehicles, it was possible to further reduce the number of body components and signiﬁcantly increase the level of automation in the production process as compared to the Audi A8 predecessor model.

The static torsional rigidity of the new Audi A8 body is 60 % higher than that of the previous Audi A8 body. A crucial contribution is made to the increased rigidity level by the advanced Audi Space Frame structure.

SSP282_027

Characteristic features of the new structure:

– Large castings with numerous integrated

functions and a high degree of joint strength

– IHF* sections – optimum cross sections at

all locations, for example at side of roof frame

– Sheet metal panels with high levels of local

rigidity thanks to the use of special technologies designed to achieve differing functional cross sections and structures

*IHF = Internal high-pressure forming

Body

A-pillar

The A-pillar is made of two cast shells connected by rivets and welds. The shells enclose the sill panel at the bottom and the continuous roof frame at the top.

Sill panel

Use is made for the sill panel of a 3-piece extruded section. The extruded section must be replaced in the event of sill panel damage. Depending on the nature of the damage, either the entire section has to be replaced or parts of it by way of three separating sleeves.

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SSP282_030

Rear end

The rear end has been completely redeveloped. The two large central castings are the one connecting the sill panel/ longitudinal member and the C/D-pillar connecting element.

The sill panel/longitudinal member connecting element is the largest casting. It supports the entire rear sub-frame and links the rear longitudinal member to the sill panel. Its great rigidity is designed to protect the tank in between in the event of a rear-end collision.

The C/D-pillar connecting element (large upper casting) accommodates the suspension strut at the top and the seat belt at the front, in addition to forming the terminating side section of the roof frame.

The large upper and lower castings are interlinked by way of two straight extruded sections and form the framework for the air suspension strut holder.

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Large upper castings

Extruded sections

Large lower castings

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Body

Boot lid

Foam encasing

Electronic boot lid lock with microswitch

Motor for automatic closing aid

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.

cable

SSP282_035

CatchBowden

The drive unit is only encased in foam and inserted between side panel and battery.

Automatic boot lid

Hinge mechanism (open)

Boot lid control unit J605

Button in driver's door Button on boot lid Vehicle key

Pressing the button in the driver's door or on the boot lid, or remote control actuation, effects release and motor-driven opening of the boot lid. Automatic boot lid closing can only be implemented by way of the boot lid button.

An electric motor ﬂanged directly to the swivel joint of the right boot lid hinge opens or closes the boot lid.

SSP282_036

In the event of manual boot lid actuation, the electric motor is disconnected by way of a magnetic coupling, thus permitting the boot lid to be moved by hand. On closing the boot lid, the drive is deactivated via a microswitch at the latch and the automatic closing aid activated.

As a general rule, interruption of automatic actuation always causes the boot lid to be disconnected from the drive unit and thus set to manual mode.

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.

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.

Rear doors

Large, high-strength side impact members are integrated into the door to provide even load distribution in the event of side impact.

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Seats

Backrest adjustment – The angle of the top 1/3 of the backrest can be adjusted by 15° for enhanced shoulder comfort.

Lumbar support with massage function over a length of 60 mm

Crash-active, electronic head restraint with 70 mm height adjustment

Thorax/pelvis side airbag

Backrest fan

Electric seat depth adjustment – As the structure moves forwards it pulls the padding with it and so extends the seat area by 50 mm.

A new seat concept was developed for the Audi A8 ´03. The basic seat features the following standard functions:

– Electric seat length, height and angle

adjustment – Electric backrest angle adjustment – Front crash-active head restraints (refer to

Page 21)

The basic seat can additionally be ﬁtted with

– Four-way lumbar support – Seat memory for driver and front

passenger – Electrically adjustable head restraints – Electric belt height adjusters

SSP282_116

Seat cushion fan

Extra features of sports and comfort seats:

– Electric top 1/3 backrest adjustment – Electric seat depth adjustment

Optional extras for comfort seat:

– Climate function (refer to Page 85) – and/or massage function

The massage function is implemented by way of rhythmic action of the electromechanical lumbar support, thus massaging and relaxing the back muscles.

The ﬁxed rear seat bench versions correspond to those of the front seats, with the third head restraint being fully retractable. Electric individual seats are however only available as "Basic" and "Comfort" versions.

Passenger Protection

System layout

J285/K75

T16

G 283

N95/G85

J623

J234

K145

AIRBAG

OFF

G 284

AIRBAG

AUS

E224

EIN

J533

N131

N251

G 256

G179

N199

N153

N201

E24 E25

J526

N196 N198 N197

N200

N154

N202

G180

N252

G 257

J393

J655

SSP282_068

Use is made in the Audi A8 ´03 of the 8.4E+ airbag system with the aim of attaining greater occupant safety whilst reducing the impact. This was achieved, for example, by way of twostage front airbag triggering, active front head restraints and a battery cut-off element.

Key

The wide range of sensors permits detection not only of head-on collision and side impact, but also of rear-end collisions.

E24 Driver side belt switch E25 Front passenger side belt switch E224 Airbag disabling key switch,

front passenger side

G85 Steering angle sender G179 Side airbag crash sensor,

driver side (B-pillar)

G180 Side airbag crash sensor,

front passenger side (B-pillar)

G256 Rear side airbag crash sensor,

driver side

G257 Rear side airbag crash sensor,

front passenger side

G283 Front airbag crash sensor,

driver side

G284 Front airbag crash sensor,

front passenger side

J234 Airbag control unit J285 Control unit with display

in dash panel insert

J393 Convenience system central

control unit J526 Telephone/telematics control unit J533 Data bus diagnostic interface

(gateway) J623 Engine control unit J655 Battery cut-off relay

K75 Airbag warning lamp K145 Airbag disabled warning lamp,

front passenger side

N95 Driver side airbag igniter N131 Airbag igniter 1, front passenger side N153 Belt tensioner igniter 1, driver side N154 Belt tensioner igniter 2,

front passenger side

N196 Rear belt tensioner igniter,

driver side

N197 Rear belt tensioner igniter,

front passenger side

N198 Rear belt tensioner igniter,

centre N199 Side airbag igniter, driver side N200 Side airbag igniter,

front passenger side N201 Rear side airbag igniter,

driver side N202 Rear side airbag igniter,

front passenger side N251 Curtain airbag igniter, driver side N252 Curtain airbag igniter,

front passenger side

T16 16-pin connector

(diagnostic connection)

Passenger Protection

Block diagram

J655

F138

G283 G284 G179

E224

J234

N95

Key

E24 Driver side belt switch E25 Front passenger side belt switch E224 Airbag disabling key switch,

front passenger side

F138 Airbag coil connector/return spring

with slip ring

G179 Side airbag crash sensor,

driver side

G180 Side airbag crash sensor,

front passenger side

G256 Rear side airbag crash sensor,

driver side

G257 Rear side airbag crash sensor,

front passenger side

G283 Front airbag crash sensor,

driver side

G284 Front airbag crash sensor,

front passenger side

N131

N202N199 N200 N201

J234 Airbag control unit J655 Battery cut-off relay

N95 Driver side airbag igniter N131 Airbag igniter 1, front passenger side N153 Belt tensioner igniter 1, driver side N154 Belt tensioner igniter 2,

front passenger side N196 Rear belt tensioner igniter, driver side N197 Rear belt tensioner igniter,

front passenger side N198 Rear belt tensioner igniter, centre N199 Side airbag igniter, driver side N200 Side airbag igniter,

front passenger side N201 Rear side airbag igniter,

driver side N202 Rear side airbag igniter,

front passenger side

G180

G256 G257 E24 E25

4 5 6 7

N251 Curtain airbag igniter, driver side N252 Curtain airbag igniter,

front passenger side

Colour code

= Input signal

= Output signal

= Positive supply

= Earth

N198N251 N252 N153 N154 N196 N197

Additional signals

Battery A (positive)

Positive connection to starter B and alternator C

Terminal 58s

Drive system CAN (High)

Drive system CAN (Low)

Crash signal

Airbag disabled warning lamp, front passenger side K145

SSP282_069

Passenger Protection

Safety systems

2-stage front airbags

The 2-stage triggering of the front airbags provides optimum restraint in crash situations at around 30 km/h. There is a separate ﬁring pellet for each stage in the driver's and front passenger's airbag. These ignite successively at speciﬁed time intervals.

Ring airbag

A so-called "ring airbag", which inﬂates like a life belt, is used on the driver's side. This radial inﬂation method affords particular protection to drivers sitting very close to the steering wheel. The centre of the steering wheel does not move as the airbag unfolds and is inﬂated in the form of a ring. A rectangular fabric layer is additionally sewn to three sides of the ring. One side is left free to allow the airbag to slide over the nonmoving centre section of the steering wheel.

SSP282_070

This airbag design satisﬁes the requirements of the latest American legislation and involves compliance with biomechanical values for so-called "Out Of Position" (OOP) driver posture. If the driver's head or upper part of the body is very close to the steering wheel at the time of airbag unfolding (OOP), this airbag concept can prevent serious injury.

Front passenger's airbag deactivation

An optional feature of the Audi A8 ´03 is a new airbag disabling key switch for the front passenger's side E224. Two resistance paths are integrated into this switch to permit detection of individual faults. A fault in the key switch is indicated by ﬂashing of the front passenger's side airbag disabled warning lamp K145 located in the centre console next to the hazard warning switch.

Front knee airbags (USA)

SSP282_081

The USA version of the Audi A8 ´03 is ﬁtted with driver's and front passenger's knee airbags as standard, thus optimising driver and front passenger movement in a crash situation.

SSP282_114

In this way, severe impact in the knee zone is avoided. Knee airbags are required by legislation in the USA.

Passenger Protection

Detection of rear-end collision

Rear-end collisions are detected by way of a sensor in the airbag control unit J234 and a plausibility function involving the driver's and front passenger's front airbag crash sensors G283 and G284.

Up-front sensors

For the ﬁrst time, use is made in the Audi A8 ´03 of so-called up-front sensors.

Lateral acceleration sensors

These take the form of two additional frontend acceleration sensors on the right and left beneath the corresponding headlight.

SSP282_072

Further acceleration sensors are located at the B and C-pillars.

C-pillar sensor B-pillar sensor

SSP282_073

Active head restraints

The front seats of the Audi A8 ´03 are provided with active head restraints. With this system, the head restraints move forwards in the event of a rear-end collision to shorten the distance between head and restraint.

The danger of cervical vertebrae injury is greatly diminished by reducing the relative acceleration between shoulder and head. In head-on collision situations, the mechanics of centrifugal weight are neutralised.

Belt tensioners

Five belt tensioners are ﬁtted as standard. There is no centre belt tensioner if the rear seats are electrically adjustable.

SSP282_082

Passenger Protection

Battery cut-off relay J655

The battery cut-off relay is a battery isolating element designed to disconnect starter and alternator power from the electrical system in the event of a crash.

Terminal Pin Input/output Description

30, battery A Input

(screw connection)

87 B Output

(screw connection)

Terminal 15 1 Input

(plug connection)

Vehicle earth 2 Input

(plug connection)

Crash signal 3 Input

(plug connection)

Diagnosis 4 Input

(plug connection)

Block diagram

J644 Energy management control unit J655 Battery cut-off relay

term. 30/battery

bat.

Output

Positive power supply,

interruptible

Earth from

airbag control unit J234

Crash signal from

airbag control unit J234

Diagnostic wire from

airbag control unit J234

J644

SSP282_076

J655

Fitting location

The battery cut-off relay is located in front of the battery.

Triggering

The airbag control unit J234 provides the battery cut-off element with the triggering command via a discrete wire. Triggering of this element by the airbag control unit causes a white panel to appear in the element window instead of a copper coil. Following isolation, the battery cut-off element can be manually reset by way of the yellow knob.

Control element test

The control element test in the airbag control unit also triggers the battery cut-off relay. It should be ensured that the relay is manually reset, as otherwise the battery cannot be charged.

SSP282_083

SSP282_079

Reset knob

Window

SSP282_077

Engine, Mechanics

2000

4000

6000

406080

Technical data

V8 4.2 l 5V engine

Engine code letters: BFM

Capacity:

4,172 cm

460

440

Bore: 84.5 mm

Stroke: 93.0 mm

Compression ratio: 11 : 1

Power: 246 kW (335 hp)

at 6,500 rpm

Torque: 430 Nm at 3,500 rpm

Camshaft adjustment range: 22° CS advance

Valves: 5 per cylinder

Engine management: ME7.1.1

Emission standard: EU 4

420

400

380

360

340

320

Torque [Nm]

300

280

260

Power [kW]

Engine speed [rpm]

SSP282_002

Firing order: 1 - 5 - 4 - 8 - 6 - 3 - 7 - 2

Capacities: 7.5 l engine oil (incl. ﬁlter)

Consumption: Urban: 17.5 - 17.6 l/100 km

Non-urban: 8.7 - 8.8 l/100 km Average: 11.9 - 12.0 l/100 km

Acceleration 0 - 100 km/h: 0 - 80 km/h – 4.8 s

0 - 100 km/h – 6.3 s

Fuel: Premium Plus Unleaded

98/95 RON

CS = Crankshaft

SSP282_012

V8 3.7 l 5V engine

Engine code letters: BFL

Capacity:

3,697 cm

460

440

240

Bore: 84.5 mm

Stroke: 82.4 mm

Compression ratio: 11 : 1

Power: 206 kW (280 hp)

at 6,000 rpm

Torque: 360 Nm at 3,750 rpm

Camshaft adjustment range: 13° CS advance

Valves: 5 per cylinder

Engine management: ME7.1.1

Emission standard: EU 4

420

400

380

360

340

320

Torque [Nm]

300

280

260

Power [kW]

Engine speed [rpm]

SSP282_001

Firing order: 1 - 5 - 4 - 8 - 6 - 3 - 7 - 2

Capacities: 7.5 l engine oil (incl. ﬁlter)

Consumption: Urban: 17.1 - 17.3 l/100 km

Non-urban: 8.6 - 8.8 l/100 km Average: 11.7 - 11.9 l/100 km

Acceleration 0 - 100 km/h: 0 - 80 km/h – 5.6 s

0 - 100 km/h – 7.3 s

Fuel: Premium Plus Unleaded 98/95 RON

SSP282_011

Engine, Mechanics

V8 5V 3.7 l/4.2 l engine

The 3.7 l and 4.2 l V8 engines were adopted from the predecessor model with certain modiﬁcations.

These modiﬁcations relate to the intake and exhaust systems and are described in the following.

Variable-intake manifold in 4.2 l engine

This takes the form of a 2-stage variable-intake manifold made of a die-cast magnesium alloy, bonded and bolted together in four sections.

The two-stage design permits the use of two intake paths with large cross section.

Design and operation are described in SSP 217.

The intake manifold must be replaced as a complete unit when performing repairs.

SSP282_013

– Long intake path, 705 mm – Changeover ﬂap closed for high torque

Each of the two splined shafts is ﬁtted with four ﬂaps per cylinder bank. The shape of the rubber-encased ﬂaps ensures unimpeded air ﬂow in the torque position and reliable power position sealing of the duct. This is a prerequisite for utilisation of the gas-dynamic resonance effects. In the power position, the backs of the ﬂaps take on the shape of the duct wall, thus allowing low-resistance intake air ﬂow into the cylinders.

SSP282_014

Mechanical couplings provide a link with the vacuum units for adjustment of the two shafts and thus the intake manifold ﬂaps.

– Short intake path, 322 mm – Changeover ﬂap open for high power

with high air throughput

Changeover from long to short at 4,480 rpm Changeover from short to long at 4,320 rpm

SSP282_016

SSP282_015

Engine, Mechanics

Variable-intake manifold in 3.7 l engine

Changeover ﬂap, stage 3

Vacuum unit Changeover ﬂap, stage 3

Vacuum unit Changeover ﬂap, stage 2

Intake air (inlet)

Changeover ﬂap, stage 2 (open)

Resonance tube, cyl. 5 (inlet end)

From electronic throttle

Throttle valve

Injector mounts

SSP282_017

This is the same 3-stage variable-intake manifold as previously ﬁtted in the V8 engine.

Operation of the 3-stage variable-intake manifold is described in SSP 217.

Due to the piston stroke of only 82.4 mm, three resonance tube lengths are required to achieve resonance effects in the lower engine speed range.

Changeover points:

– Long to short

at 3,280 rpm

– Short to long

at 3,120 rpm

– Short to shorter

at 5,120 rpm

– Shorter to short

at 4,920 rpm

Air cleaner

A round ﬁlter is employed instead of a ﬂat ﬁlter to achieve a larger ﬁlter surface area for more air throughput in view of the different amount of space available.

Furthermore, an additional intake air ﬂap in the air cleaner is opened as a function of load at engine speeds as of 3,000 rpm to attain the large volume of air required at full throttle. This ﬂap enables additional air to be drawn in from the engine compartment and reduces the air velocity in the air cleaner.

SSP282_018

SSP282_019

Engine, Mechanics

System layout

Actuators/sensors

Hot-film air-mass meter G70

Engine speed sender G28

Hall sender G40 (bank 2) and Hall sender 2 G163 (bank 1)

Lambda probe G39 (bank 1) Lambda probe II G108 (bank 2) Lambda probe after catalyst G130 (bank 1) Lambda probe II after catalyst G131 (bank 2)

Throttle valve control part J338 with Throttle valve drive G186 (electric power control) Throttle valve drive angle sender 1 G187 Throttle valve drive angle sender 2 G188

Coolant temperature sender G62

Pedal position sender/accelerator pedal module with accelerator pedal position sender G79 and accelerator pedal position sender 2 G185

Brake light switch F and Brake pedal switch F47

Clutch pedal switch F36 (manual gearbox only)

Dash panel insert CAN

Knock sensor I G61 (bank 1) and Knock sensor II G66 (bank 2)

Additional signals: – Air conditioner requirement – Cruise control switch – Term. 50, stage 1 – Automatic gearbox selector lever position

Control unit with display in dash panel insert J285

Engine control unit J623

Fuel pump relay J17

Fuel pump G6

Fuel pump II relay J49

Fuel pump G23

Injectors N30, N31, N32, N33 (bank 1)

Steering angle sender G85

ESP control unit J104

Data bus diagnostic interface J533

Automatic gearbox control unit J217

Airbag control unit J234

Intake manifold changeover valve N156 and Intake manifold changeover valve 2 N261

Left electrohydraulic engine mounting solenoid valve N144 and Right electrohydraulic engine mounting solenoid valve N145

Torque rod valve N382

Lambda probe heater Z19 (bank 1) and Lambda probe 2 heater Z28 (bank 2)

Injectors N83, N84, N85, N86 (bank 2)

Ignition coils N (no. 1 cyl.), N128 (no. 2 cyl.),

N158 (no. 3 cyl.), N163 (no. 4 cyl.)

Ignition coils N164 (no. 5 cyl.), N189 (no. 6 cyl.),

N190 (no. 7 cyl.), N191 (no. 8 cyl.)

Activated charcoal filter system solenoid

valve 1 N80

Secondary-air pump relay J299 and

Secondary-air pump motor V101

Secondary air inlet valve N112

Throttle valve control part J338

With throttle valve drive G186

Drive system CAN

Diagnosis CAN

Lambda probe 1 heater after catalyst Z29 Lambda probe 2 heater after catalyst Z30

Additional signals: – Starter relay term. 50, stage 2 – Tank leakage pump (USA only) – Air conditioner compressor (out)

Inlet camshaft timing adjustment valve 1

N205 (bank 1)

and

N208 (bank 2)

SSP282_091

Engine, Mechanics

Electrohydraulic torque reaction support

Lock nut

Shell

Top section

Connecting pipe

Bellows cap

Stress-free alignment of the torque reaction support is implemented by way of the lock nut.

Isolation diaphragm

Upper section of nozzle plate

Plastic ring with sheet metal ring

Solenoid

Bottom section

The purpose of torque reaction support is to cushion the drive shaft and propshaft torque. The position of the support bearing at the front right of the engine is ideal, as this is where the engine motion resulting from drive shaft and propshaft torque accumulates.

The torque reaction support is divided into two halves by the plastic ring, the sheet metal ring and the isolation diaphragm. Both halves are ﬁlled with ﬂuid (glycol). The isolation diaphragm is ﬂexibly linked to the plastic and sheet metal rings.

If the torque reaction support is subjected to load, the ﬂuid can be displaced between the top and bottom section by way of a connecting pipe, the dimensions of which are such that it acts as a restrictor as of a deﬁned frequency.

SSP282_020

When the solenoid is deenergised, vibration causes the plastic ring with sheet metal ring and isolation diaphragm to oscillate as well. The moments are damped slightly and thus transmitted to a lesser extent to the body.

As of an engine speed of approx. > 1,100 rpm and a vehicle speed of > 5 km/h, the solenoid is energised and attracts the sheet metal ring together with the plastic ring.

This restricts the movement of the isolation diaphragm, which can then only vibrate slightly. In this case there is a high level of vibration damping and the torque reaction support is "hard".

Exhaust system

Lambda probe II G108, cylinder bank 2

Lambda probe G39, cylinder bank 1

Lambda probe after catalyst G130

Lambda probe II after catalyst G131

Exhaust manifold

Two-stage catalytic converter

Connecting pipe

With the 4.2 l and 3.7 l engines, the exhaust system is of the dual-ﬂow type. It consists of two underbonnet catalytic converters, two ﬂexible decoupling elements, two reﬂection-type front silencers, an absorption-type centre silencer and two reﬂection-type rear silencers with visible tail pipes. The catalytic converters are of the twostage type and ﬁtted with a ceramic monolith.

SSP282_028

Thin-walled ceramic monoliths are used to improve cold starting behaviour. On environmental grounds, the centre silencer is ﬁtted with long-ﬁbre glass wool instead of basalt wool. A connecting pipe is located directly upstream of the centre silencer. This forms the joint between the two exhaust pipes required for acoustic reasons.

Engine, Mechanics

Fuel tank

The fuel tank capacity is approximately 90 litres. The basic unit consists of two plasma-welded stainless steel shells. There are no differences between petrol and diesel engine versions.

The ﬁller neck is a single piece and welded to the basic unit. For reasons of crash safety, the centre section of the ﬁller neck takes the form of a corrugated tube.

In crash situations, this section is subject to deﬁned deformation to prevent cracks and fuel spillage.

To create the best possible ergonomic conditions for the rear passengers in combination with maximum luggage compartment volume, the two tank compartments are shallower than in the predecessor model.

The additional expansion tank has been taken out of the ﬁller pipe and moved to the fuel tank.

The tubing system for the tank breather at the ﬁller pipe has been considerably simpliﬁed as compared to the predecessor model. With the exception of diesel vehicles, the pipe connections have been converted to quickrelease couplings.

A new feature is the use of a 2-stage delivery pump for each tank chamber in separate reservoirs.

The fuel level is measured by two immersion tube senders combined with two angle senders.

Fuel ﬁller neck

The switch from plastic to stainless steel was necessary for compliance with American LEV II legislation, which demands a further signiﬁcant reduction in permissible emission levels.

Activated charcoal ﬁlter

Tank compartment breather

Diagnostic connection

SSP282_007

Interior of fuel tank (ﬁlling)

Filler pipe

Breather pipe to ﬁller pipe

Float-type shutoff valve

Reservoir with pump unit, right

Bafﬂe housing of expansion tank

Overﬂow channel

The fuel is conveyed via the ﬁller pipe into the right tank chamber (as viewed in direction of travel). The fuel passes via an additional overﬂow channel at the end of the ﬁller pipe predominantly into the right pump reservoir.

Use of the small overﬂow channel ensures that even small quantities of fuel (e.g. ﬁlling from canister) pass directly into the pump reservoir.

The breather function for the side compartments is provided by two breather pipes to the main chamber.

Reservoir with pump unit, left

SSP282_006

Routing the ﬁller pipe beneath the longitudinal member means that the lowest point of the pipe is not at the connection to the fuel tank, thus producing a siphon effect.

A residual quantity of fuel remains in the ﬁller pipe. This necessitates a separate pipe to the ﬁller neck for the main chamber breather function and for OBD II leakage diagnosis.

When the tank is full, the ﬁller hose is closed by a ﬂoat-type shutoff valve at the end of the ﬁller pipe.

Engine, Mechanics

Expansion tank

Inlet pipe from tank ﬁller neck

Breather pipe

Float-type rollover valve

Suction jet pump intake connection

The expansion tank (capacity approx. 2 litres) consists of a plastic housing clipped to the upper shell of the tank.

The internal expansion tank houses a ﬂoattype rollover valve and a small suction jet pump which constantly pumps the tank empty whilst driving.

Float-type shutoff valve

SSP282_009

Function

The main functions of the ﬂoat-type rollover valve are as follows:

– Closing-off of pipe to ﬁller neck in the

event of rollover – Closing in dynamic driving mode – Closing by rising of ﬂoat in valve in the

event of a brief excess of fuel in the tank

due to sloshing

Closing-off of the pipe to the activated charcoal ﬁlter stops fuel overﬂowing into it.

Two-stage fuel pumps

Return

Main stage delivery end

Main stage suction end

Overﬂow

Reservoir

Pre-stage delivery end

Main stage suction end

The two fuel pumps (petrol engine) are of the two-stage ﬂow type.

The ﬁrst stage (pre-stage) pump unit draws in fuel from the bottom of the tank and conveys it into the reservoir. This ensures that even small residual quantities can be transported. The second stage (main stage) pump unit draws in fuel directly from the reservoir.

Main stage pump unit

Pre-stage pump unit

Pre-stage suction end

Fuel tank

SSP282_003

The reservoirs with pumps and immersion tube senders rest on and are clipped to the bottom of the tank. Flanged covers provide access to the components.

Single-stage pumps are used for diesel engines (Common Rail). On account of the higher viscosity of diesel fuel, pre-delivery (extraction from bottom of tank) is not implemented by way of separate pump units, but rather by suction jet pumps.

Engine, Mechanics

Fuel system (hydraulics)

Pressure regulator (4 bar)

Fuel pump G23 Fuel pump G6

Suction jet pump

When the ignition is switched on (terminal 15), the fuel pump G23 conveys a maximum volume to the pressure regulator at the fuel rail to achieve short starting times. The pump G6 also conveys fuel to the pressure regulator and additionally into the pipes for the two suction jet pumps in the side tank compartments.

The suction jet pumps convey the fuel from the side compartments "diagonally" into the pump reservoirs.

Such pipe routing prevents dry running of a pump in critical driving situations such as cornering or if the vehicle is at an extreme angle. The return pipe is shared by both reservoirs.

If one reservoir is full, the pipe is closed by a non-return valve and the entire return volume runs into the second reservoir.

If both reservoirs are full, the non-return valves are overridden and the fuel runs into the tank.

SSP282_005

Tank senders

The fuel level is sensed by two immersion tube senders and two angle senders. A new feature is the design of the angle sender, which is equipped with a magnetically passive position sensor.

The ceramic substrate is provided with 51 series-connected ﬁlm resistors with individual pick-off. Fitted with a small clearance on top of this is a magnetically soft foil with the same number of spring contacts. The magnetic position sensor beneath the ceramic substrate pulls the spring contacts onto the pick-offs. The electrical output signal varies proportionally as a function of the position of the magnet.

Thanks to the magnetic coupling it was possible to provide a hermetic seal for the measurement system.

Magnetically soft foil

Ceramic substrate with ﬁlm resistors

Magnetic position sensor

SSP282_010

Advantages:

– Longer service life thanks to noncontacting

measurement system – Protection against dirt and deposits – Low contact currents

Fuel gauge sender 3 G237 (immersion tube sender, 70 - 158 W)

Fuel gauge sender 4 G393 (angle sender, 50 - 300 W)

SSP282_008

Fuel pump G23

Fuel pump G6

Fuel gauge sender G (immersion tube sender, 70 - 158 W)

Fuel gauge sender 2 G169 (angle sender, 50 - 300 W)

Direction of travel

Characteristic curve adaption

Control unit with display in dash panel insert J285

Fuel gauge G1

Engine, Mechanics

Determining fuel level

The fuel level is determined by way of a logical system of immersion tube and angle sender signals.

a - Low levels are determined exclusively by

way of the angle sender measured values

b - High levels are determined exclusively by

way of the immersion tube sender measured values.

SSP282_004

The sender signals are evaluated by the dash panel insert. All senders are connected in parallel.

The wires are bunched beneath the fuel tank, thus enabling resistance measurements to be taken without the need for further dismantling.

c - Medium levels are determined by a

combination of all sender signals

Automatically controlled starting

The automatic start control is integrated into the engine control unit.

A new feature is that starter control is no longer implemented by way of the ignition/ starter switch D (switching of terminal 50), but rather it is performed automatically by the engine control unit.

Release for starter actuation is always transmitted by the entry and start authorisation control unit J518 to the engine control unit J623.

In addition to general release by the immobilizer, the following start release conditions also have to be satisﬁed:

– Start signal from entry and start

authorisation switch E415 or entry and start authorisation button E408

– Clutch pedal pressed, signal from clutch

pedal switch F194 (manual gearbox only)

– Selector lever position P or N (automatic

gearbox control unit J217)

– In the event of start signal via entry and

start authorisation button E408, brake must be pressed (signal from brake light switch F via separate interface)

As a safeguard, P/N signal or signal from clutch pedal switch F194 must be applied to the separate interfaces of the two control units (J623 and J518).

Additional safeguard, as entry and start authorisation button E408 can be actuated by front passenger.

Engine, Mechanics

Sequence of operations

1 Entry and start authorisation switch E415/

entry and start authorisation button E408

2 Entry and start authorisation control unit

J518

The entry and start authorisation control unit checks for authorisation – in the form of information on selector slide position N or P – from the automatic gearbox control unit J217 and for brake application in the case of a start signal from the entry and start authorisation button E408.

3 Engine control unit J623

Application of selector slide position P/N or "clutch pressed" information to the engine control unit (separate interface) causes the two starter relays J53 and J695 to be actuated simultaneously. The relays then switch terminal 50 for starter actuation. The starter operates and cranks the engine. On exceeding a deﬁned engine speed, the engine control unit J623 recognises that the engine has started and the relays are deenergised (thus terminating starting process).

As a safeguard, two relays are connected in series. In the event of fusion welding of the make contacts (relay remains closed following deenergisation), the engine control unit J623 can thus interrupt the circuit (terminal 50) by way of the other relay in each case.

The two relays are deenergised alternately in order to ensure even make contact wear (break spark) in both relays. The deenergisation sequence alternates.

The driver triggers a brief start signal (min. 20 ms) by turning the ignition key to start position or by pressing the entry and start authorisation button E408.

If the start prerequisites have been satisﬁed, the entry and start authorisation control unit J518 transmits a start request – terminal 50 ON – to the engine control unit J623.

The entry and start authorisation control

unit J518 also controls the terminal 15 and terminal 75x circuits.

Relay operation is monitored and faults

diagnosed by evaluating the alternating deenergisation with the aid of the terminal 50R interface.

The terminal 50R interface represents a link with terminal 50 and provides the engine control unit J623 with feedback for start control/diagnosis.

Automatically controlled starting is not permitted in the event of undervoltage or a system fault.

The engine can however be started manually by way of corresponding start signal actuation.

To relieve the load on the starter and battery, the relay actuation time is limited to approx. 10 seconds per starting operation (automatic or manual starting).

Block diagram

E415

75x

1 2

58s

E408

210 210

STOP START

J518

N376

50R

1 2

J329 J53 J695J694

D1 Inhibitor reading unit E408 Entry and start authorisation button E415 Entry and start authorisation switch J53 Starter motor relay J329 Terminal 15 voltage supply relay J518 Entry and start authorisation

control unit

Colour code

= Input signal

= Output signal

= Positive supply

50R

J623

SSP282_024

J623 Engine control unit J694 Terminal 75x voltage supply relay J695 Starter relay 2 N376 Ignition key withdrawal lock magnet

Additional signals

F - Brake light switch

Manual gearbox -> F194 Clutch pedal switch Automatic gearbox -> Selector lever position from automatic gearbox control unit J217

= Earth

Terminal 50/starter

Engine, Mechanics

Explanatory notes on internal control unit sequence chart

Request for starting (terminal 50 ON from entry and start authorisation control unit J518) energises the two relays. Locking-in takes place during the initialisation phase of engine control unit J623.

Term. 15

Start request from

driver authorisation

system

Start request brieﬂy activated

After initialisation, the engine control unit assumes further starter control tasks as described under item 3.

Start request retained manually

Engine start

recognition

(engine speed)

Relay deenergisation by

engine control unit

Term. 50R/diagnosis

Engine control unit

initialisation

Engine control unit active

Engine speed increases

Starter speed

Relay deenergisation

Starter operation feedback signal

Locking-in

Engine control unit active

Starting Engine running

Ignition on

SSP282_064

Gearbox

To satisfy high comfort requirements, the Audi A8 ´03 features a new 6-speed automatic gearbox capable of handling a high engine torque of max. 600 Nm.

Design and operation of the 09E gearbox are described in SSP 283 (Part 1) and SSP 284 (Part 2).

Two different versions are available:

– 420 Nm for the V8 5V 4.2 l or

3.7 l engine and

– 600 Nm for the V8 TDI 4.0 l or

6.0 l W12 engine

Technical data

Designation: 09E

Factory designation: AL 600-6Q

ZF designation: 6HP-26 A61

Type: 6-speed planetary

gearbox, featuring electrohydraulic control with hydrodynamic torque converter and slip-controlled lockup clutch

Control: Via mechatronic system

(integration of hydraulic control unit and electronic control to form one unit)

SSP282_043

Max. torque transmission: 420 Nm for

V8 5V 4.2 l /3.7 l engine

600 Nm for V8 TDI 4.0 l /W12

6.0 l engine

Front/rear axle torque distribution: 50/50

Gear oil capacity (total): 10.4 litres ATF

Gear oil capacity (replacement): 10 litres ATF

Total weight: approx. 138 kg

(420 Nm version)

approx. 142 kg (600 Nm version)

Gearbox

Highlights of automatic gearbox 09E (AL 600-6Q)

The 6-speed planetary gearbox is based on the Lepelletier principle. This concept is characterised by harmonic gear ratio steps and the implementation of six forward gears and one reverse gear with only ﬁve selector elements.

Use is made in this gearbox of a new internal gear oil pump featuring a lower delivery volume and reduced leakage.

In addition, it was possible to achieve optimisation of the oil supply with lower leakage rates in the hydraulic control system.

The "stationary disconnection" function reduces engine output when the vehicle is stopped with a gear engaged by interrupting power transmission.

A particularly noteworthy feature of the 09E automatic gearbox is the relocation of the front-axle differential (ﬂange shaft) to in front of the torque converter.

SSP282_044

The distance between ﬂange shaft and engine ﬂange is now only 61 mm (01L = 164 mm).

SSP282_045

The mechatronic system integrated into the gearbox housing is a new development, combining the hydraulic control unit, sensors, actuators and electronic gearbox control unit in a coordinated assembly.

All data exchange with the vehicle periphery takes place via the drive system CAN, thus reducing the number of vehicle periphery interfaces to a minimum (11 pins) and at the same time enhancing operational reliability.

SSP282_046

Gearbox

In terms of the following functions, there are interesting new aspects to the shift mechanism in the new Audi A8 '03:

– Shift mechanism kinematics – Ignition key removal lock – Selector lever lock – Selector lever lock emergency release – Selector lever/lock button kinematics

Ignition key removal lock

Major modiﬁcations have been made to operation of the ignition key removal lock and selector lever lock (shiftlock). On account of the new entry and start authorisation switch E415, there is no mechanical link between the shift mechanism and ignition lock (locking cable).

Selector lever lock emergency release

This modiﬁcation means that the selector lever remains locked in position "P" in the event of malfunctions or power supply failure (e.g. battery ﬂat). Selector lever lock emergency release is provided to enable the vehicle to be moved (e.g. towed) in such situations.

Selector lever/button kinematics

To prevent inadvertent shifting into selector lever position "S", a change has been made to the selector lever kinematics such that switching to "S" involves pressing the button in the gearstick knob.

A small gear mechanism is provided in the gearstick knob to reduce the required button operating force.

The locking rod is actuated by the application of pressure, which means changes have also been made to kinematics and gearstick knob assembly (refer to Workshop Manual).

SSP282_048 SSP282_049

Front axle

Running Gear

The familiar four-link front axle was retained for the Audi A8 '03. A signiﬁcant new feature is the air suspension in combination with electronically controlled dampers (refer to Section on air suspension).

Front axle highlights

– Subframe – Auxiliary frame – Anti-roll bar – Wheel bearing housing – Wheel bearing with wheel speed sensing – Mounting bracket for damper unit

All axle components are new on account of the geometric and kinematic modiﬁcations as compared to the predecessor model, the air suspension and the weight reductions achieved.

Front axle design and operation are described in SSP 285.

SSP282_050

Running Gear

Rear axle

The rear axle is a more advanced version of the familiar Audi A8 trapezium-link axle.

Rear axle highlights

– Use of air suspension in conjunction with

electronically controlled damping

– Aluminium subframe to help

reduce weight

– Connection of anti-roll bar to trapezium

link

– Use of shorter track rod to reduce change

in toe on compression and extension of suspension

– Use of ball studs to connect wheel bearing

housing and track rod, thus reducing secondary spring rate

– Use of slotted bonded rubber bushes in

upper transverse link and connection between trapezium link and subframe

All axle components are new on account of the geometric and kinematic modiﬁcations as compared to the predecessor model, the air suspension and the weight reductions achieved.

Rear axle design and operation are described in SSP 285.

SSP282_051

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

EDC instead of PDC damping

system are as follows:

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.

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.

SSP282_052

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_053

Running Gear

System layout

Front information and display and operating unit control unit J685

Adaptive suspension control unit

Rear axle acceleration sensors

Control unit with display in dash panel insert J285

Rear axle air suspension struts

Pressure accumulator

Front axle air suspension struts

SSP282_054

Rear axle level sensors

Front axle level sensors

Design and operation of 4-level air suspension are described in SSP 292.

Solenoid valve block

Compressor

Front axle acceleration sensors

Electric parking brake

The brake pads are applied by way of a spindle mechanism.

Gear unit and motor are ﬂanged to the brake caliper.

Implementation of the parking brake function involves translating the rotation of the drive motor into a very short brake piston stroke.

This is achieved through the use of a swash plate mechanism in combination with the spindle mechanism.

The emergency braking function is initiated via the parking brake button and transmitted to all four wheels by the brake hydraulics.

Brake caliper

Brake piston

The following functions are provided by the electric parking brake:

– Parking brake function – Emergency braking function – Holding function when driving off on a hill – Brake pad wear indicator

Design and operation of the electric parking brake are described in SSP 285.

Electric motor

Toothed belt

Swash plate mechanism

Electrical connection

SSP282_055

Brake disc

Spindle

Running Gear

ACC (Adaptive Cruise

Control)

Adaptive Cruise Control is a new system designed to assist drivers and offers a much wider range of functions than the conventional Tempomat.

Driver convenience is further enhanced, as fewer accelerator and brake pedal operations are required. Speed restrictions and safety factors are reliably observed and the ﬂow of trafﬁc thus better regulated.

Summary of Adaptive Cruise Control (ACC)

The basic Adaptive Cruise Control function is to maintain a driver-selectable distance from the vehicle in front. ACC thus represents the logical next step on from the original cruise control system.

The distance from and speed of the vehicle in front are determined by a radar sensor. If the distance is greater than desired, the vehicle is accelerated until the required speed input by the driver is achieved.

SSP282_057

If the distance is less than desired, the vehicle is decelerated by reducing power, changing gear and if necessary applying the brakes.

In the interests of comfort, maximum possible braking is restricted to approx. 25 % of the maximum deceleration potential of the brake system (full braking).

The control action is designed to assist the driver and thus contributes to greater road safety.

In certain trafﬁc situations, active braking by the driver may still be necessary.

ACC system limits

Radar sensor

– ACC is designed to assist the driver and

is not a safety system.

– ACC is not a fully autonomous driving

system.

– ACC provides control in a speed range of

30 - 200 km/h. – ACC does not react to stationary objects. – Radar operation is impaired by rain,

spray and slush. – Tight bends may restrict operation on

account of the limited radar detection

range.

An adapter plate permits ﬁtting and adjustment at a holder bolted to the centre of the bumper bracket.

For details, refer to current Workshop Manual.

Design

Sender and control unit are integrated into one housing - the distance regulation control unit J428. The entire assembly has to be replaced if the control unit is defective.

Holder

Vertical adjusting screw

Distance regulation control unit J428 with radar sensor

Mounting hole

SSP282_058

Horizontal adjusting screw

Running Gear

Setting desired speed

The desired speed is the maximum speed to be controlled by the ACC on an open road (corresponds to cruise control system function).

Pressing the SET button stores the current speed as desired speed.

The set speed is displayed by a bright red LED in the speedometer rim and the "ACC active" symbol appears in the speedometer.

The "ACC active" status is indicated by faint red illumination of all LEDs in the range between 30 and 200 km/h.

SSP282_061

SSP282_060

Setting desired distance

The desired distance from the vehicle in front can be set by the driver in four stages. The distance set by the ACC is governed by the respective vehicle speed. The distance increases with increasing vehicle speed.

The minimum setting ensures compliance with the permissible safety distance when travelling at a constant speed in trafﬁc.

The desired distance from the vehicle in front is set by means of the sliding switch on the stalk. Actuation of the switch increases or reduces the distance by one stage each time.

The desired distance selected determines the vehicle acceleration dynamics.

SSP282_059

The chosen distance is brieﬂy indicated on the info line in the speedometer centre display. The centre display is activated the ﬁrst time the button is pressed. The number of bars between the vehicles displayed corresponds to the distance stage selected in each case. The distance stage can be set for each driver.

Design and operation of the ACC are described in SSP 289 – Adaptive Cruise Control. Pay attention to operating instructions and manuals.

SSP282_062

Electrical System

Bus topology

Control unit with

The increasing demand for additional functions and convenience in the vehicle calls for the use of ever more wide ranging electronics. The increased use of electronics also requires a new approach to data transfer between the individual control units. This also applies to the Audi A8 ´03, in which more than 70 control units have to communicate.

display in dash panel

insert J285

Distance regulation

control unit J428

CAN

Electric park and

handbrake control

unit J540

Engine control unit

Headlight range

control unit

J623

Internal bus link

Diagnostic connection T16

Airbag control unit

J431

Engine control

unit 2 J624

J234

ABS with EDL

control unit

Adaptive

suspension control

unit J197

Dash panel insert CAN

Diagnosis CAN

J104

Automatic gearbox

control unit

J217

Adaptive cruise control

Drive system CAN

Convenience CAN

Anti-theft/

tilt system control

unit J529

LIN

Driver side door

control unit J386

Boot lid control unit

J605

Convenenience

system central

control unit J393

Front passenger

side door

control unit J387

Wiper motor control

unit J400

On-board power

supply control unit

J519

Rear left door

control unit J388

Garage door

operation control

unit J530

On-board power

supply control unit 2

J520

Rear right door

control unit J389

Multifunction

steering wheel

E221

Steering column

electronics control

unit J527

Seat adjustment

control unit

J136

Steering angle

sender G85

Front passenger seat adjustment

control unit J521

Control unit for rear

information display

and operating

Front information

display and operating

unit control unit J523

right

unit J649

Rear DVD changer

R162

Telephone/

telematics control

unit J526

Bluetooth

Control unit for rear

left

information display

and operating

unit J648

Telephone

handset

R37

DSP control unit

J525

Data bus diagnostic

interface J533

CD ROM drive

R92

CD changer

R41

Chip card reader

control unit

J676

MOST bus

Navigation system

control unit

J401

TV tuner

R78

Digital radio

R147

Radio module R

Fresh-air blower

control unit

J126

Climatronic control

unit J255

Rear Climatronic

control and

display unit E265

LIN

Driver side rear seat

ventilation control

unit J674

Heated windscreen

control unit J505

Rear seat

adjustment with

memory control

unit J522

Tyre pressure

monitor control unit

J502

Front passenger

side rear seat

ventilation

control unit J675

Rear left footwell

heater element Z42

Trailer detector

control unit J345

Sun roof electronics

control unit J528

Sliding sun roof

motor V1

Rear right footwell

heater element Z43

Energy

management

control unit J644

Additional heater

control unit J364

Auxiliary heating

radio controlled

receiver R64

Driver seat ventilation

control unit J672

Entry and start

authorisation

control unit J518

Driver identiﬁcation

control unit J589

Front passenger

seat ventilation

control unit J673

Parking aid control

unit J446

SSP282_063

LIN

Electrical System

The familiar CAN bus (two-wire bus) is supplemented by the following bus systems:

– LIN bus (single-wire data bus) – MOST bus (optical data bus) – Bluetooth

LIN bus

LIN stands for Local Interconnect Network.

Local Interconnect means that all control

units are located within a limited structural space (e.g. roof). This is also referred to as "local sub-system".

(wireless data bus)

Data are exchanged between the individual LIN bus systems in a vehicle by one control unit in each case using the CAN data bus.

The LIN bus system is a single-wire data bus. The wire has a basic colour (violet) and a code colour. The wire cross-section is 0.35 mm not necessary.

The system permits data exchange between one LIN master control unit and up to 16 LIN slave control units.

Data bus diagnostic interface (gateway)

. A screen is

Design and operation of the LIN bus are described in SSP 286 – New data bus systems.

LIN master

LOCAL INTERCONNECT NETWORK

LIN slave 1

Diagnosis CAN

Diagnostic connection

SSP282_031

LIN slave 2

MOST bus

The term "Media Oriented Systems Transport" signiﬁes a network featuring media-oriented data transport. This means that, in contrast to the CAN data bus, address-oriented messages are transmitted to a speciﬁc receiver.

This technique is used in Audi vehicles for the transfer of infotainment system data.

Media Oriented Systems Transport

The infotainment system offers a wide range of modern information and entertainment media. In addition to the familiar CAN bus systems, use has been made for the ﬁrst time in the Audi A8 ´03 of an optical data bus system.

Design and operation of the MOST bus are described in SSP 286 – New data bus systems.

The name of this data bus system is derived from "Media Oriented Systems Transport (MOST) Cooperation". This is an association formed by various motor vehicle manufacturers, their suppliers and software companies with a view to developing a standard high-speed data transfer system.

System manager

Sound system

Operating unit

SSP282_034

Display

Electrical System

Bluetooth

BluetoothTM is an internationally standardised remote control data interface. It permits control or monitoring of even minute units using radio waves.

The primary aim when developing this new type of interface was to create a wireless alternative to cable links, which used to be susceptible to interference and inconvenient and frequently featured incompatible connectors.

More and more manufacturers are making use of "Bluetooth example for wireless interconnection of notebook and mobile phone accessories.

As initiator and main contributor to the development of this new transmission technology, the Swedish company Ericsson chose the name "Bluetooth". The name originates from the Viking king Harald Blåtand II (Danish, literally meaning "Blue Tooth"), who lived around 1000 years ago in Denmark and Norway.

" radio wave technology for

Design and operation of the BluetoothTM are described in SSP 286 – New data bus systems.

Motor vehicle applications

– Wireless telephone receiver – Wireless mobile phone – Hands-free unit with no additional adapters – Wireless internet access – Access for PCs and Notepads

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Vehicle electrical system

A major factor in terms of vehicle reliability is one which is never even seen: the electrical system.

Use is made for the Audi A8 ´03 of a customerspeciﬁc one-piece modular wiring harness. "One-piece" means that power is supplied for all essential electrical functions from a single continuous wiring harness. The only isolating points are at the doors, roof module and engine.

"Customer-speciﬁc" means that each wiring harness is designed to serve exactly the equipment ordered by the customer. The wiring harness is subdivided into individual logic modules, each of which is responsible for a clearly deﬁned range of functions.

A plastic optical ﬁbre is ﬁtted for the transmission of optical communication and infotainment signals. Its advantages as compared to a copper conductor are its insusceptibility to electromagnetic interference, a high transmission capacity and less weight.

To achieve greater headroom, the wiring harness to the roof module has been extended to include the ﬂexible ﬂat cable (FFC). This represents a new method of solving the wiring problem in extremely conﬁned spaces (max. 2 mm between headliner and body outer skin).

Design and operation of the optical ﬁbre are described in SSP 286 – New data bus systems.

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Electrical System

Convenience and security electronics

"Advanced Key" entry and start authorisation system

"Advanced Key" can be taken to mean an "advanced locking and security system".

Design and operation are described in SSP 287 – Audi A8 ´03 Electrical Components.

It takes the form of a non-contacting key recognition system. With the "Advanced Key" package, the "Vehicle unlocking" and "Vehicle locking" functions by way of a mechanical or remote control key are supplemented by the noncontacting functions "Vehicle unlocking" and "Vehicle locking".

Functions

Advanced Key "unlocking"

The key owner enters the key detection zone next to the vehicle (less than 1.5 m from door handle) and reaches into the recessed handle moulding. A proximity sensor starts a key scan by way of an aerial. The key responds by way of radio waves and the vehicle is unlocked if authorised.

Advanced Key "starting"

The driver presses the start button, which again initiates a key scan via the passengercompartment aerials near the selector lever, at the rear centre vents and at the rear centre armrest. The remote control key provides conﬁrmation, with the result that the ignition is switched on on depressing the ﬁrst stage of the start button and the engine started on depressing the second stage. The engine is switched off with the STOP button.

In addition, the driver can start the engine with the START/STOP button (START/STOP function) without inserting the ignition key in the electronic ignition lock.

SSP282_093

Advanced Key "locking"

If the vehicle is to be locked from the outside, it is sufﬁcient to press the locking button in one of the door handles. Actuation of the locking button triggers a key scan via the door handle aerial and the vehicle is locked on conﬁrmation of the remote control key.

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Multifunction steering wheel

A new multifunction steering wheel has been introduced as standard. This is equipped with special paddles (as used in formula 1 and for the Le Mans R8) for manual shifting of the 6-speed Tiptronic

. The voice control option for radio, CD changer, telephone, navigation system and MMI address book can also be operated by way of the multifunction steering wheel.

Paddle – Paddle +

Dash panel insert display

Selection menu for: – Radio station – CD track – Telephone address book – Navigation system information

display

Menu selection control

MODE button

Press MODE button: For telephone, navigation system and radio/CD menu selection

Turn left function control: To select menu item

Press left function control: For selection within chosen menu item To accept a telephone call

Volume level/navigation message repetition control

Voice control start/termination button

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Press PTT (push to talk) button: To activate/deactivate voice control

Turn right function control: To regulate volume

Press right function control: To repeat last navigation system message

Electrical System

Infotainment

TV reception

DVD - Video

DAB - Digital radio

Telephone Telematics

Central display and control

Internet Email

Minidisc/CD audio

Both in the modern business world and in the private domain, mobile information and entertainment are becoming ever more important.

CD/DVD navigation

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In other words, vehicle occupants are becoming increasingly interested in enjoying the beneﬁts of modern media.

With this in mind, the Audi A8 ´03 is ﬁtted with an infotainment system offering a wide range of modern media.

Memory SourceCD 1

Dire Straits - Brothers in …

Tr. 12 10:56

Forward

Manual Sound

TP TMC

D2 Private

SSP282_096

Design and operation are described in SSP 293 - Audi A8 ´03 Infotainment.

Electrical System

Lighting system

Front lights

Parking light (W5W/5 W bulb)

Additional main beam Headlight ﬂasher (H7/55 W bulb)

The headlight in the Audi A8 ´03 combines both design elements and innovative technology.

Headlight versions:

– Basic halogen version H7

Dynamic headlight range control is not necessary with halogen headlights. The air suspension provides compensation for static load statuses and a thumbwheel is therefore also not required.

Adaptive light (H8/35 W bulb)

Reﬂector for adaptive light

Turn signal indicator (2 x 16 W HPV bulb - yellow)

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Dipped beam/main beam (Bi-Xenon/D2S - gas-discharge lamp)

Both bi-xenon versions feature an ellipsoid module with a moving screen to achieve both dipped beam and main beam with xenon light.

The automatic dynamic headlight range control represents a more advanced version of the standard automatic control system. It provides headlight tilt compensation not only for various load statuses but also as a dynamic function reacting to differences in running gear inclination caused by acceleration and deceleration.

– Bi-xenon version

– Bi-xenon version with integrated adaptive

light function

The headlight range control unit J431 is responsible for providing static and dynamic compensation for vehicle tilting as well as actuation of the static adaptive light function. The sensor signals of the 4-level air suspension system are picked off by the drive system CAN for control purposes. A distinction is made between the two gas-discharge lamp versions by way of appropriate encoding (1 or 2) at the headlight range control unit.

HPV stands for high-performance bulbs, which are extremely compact and have a far longer service life. They have a 25 % lower power input than conventional bulbs. Such bulbs cannot be replaced by customers.

The optional headlights with adaptive light function are a clearly visible innovative feature in the Audi A8 ´03. To implement this function, the headlights are provided with an additional reﬂector between dipped beam and main beam.

Light functions

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Adaptive light

The additional reﬂector with a 35 W H8 halogen bulb is actuated as the situation requires to ensure earlier perception of other road users or obstacles.

When reversing or parking, both adaptive lights are activated to provide the driver with a better overall view of the surrounding area.

SSP282_087

Control of the headlight functions is a complex process. It involves real time evaluation of several signals (e.g. vehicle speed, steering angle and turn signal indicator) by the headlight range control unit J431.

Electrical System

Assistant lighting system

This system adapts the vehicle lighting to the prevailing light conditions. For this purpose the light switch must be set to AUTO. The rain and light detector sensor G397 establishes the prevailing light conditions and activates the vehicle lighting system if appropriate.

Assistant lighting applies to:

– Dipped beam – Parking lights – Tail lights – Number plate light

Side lights

This is the ﬁrst Audi vehicle to be ﬁtted with LED-type lights. The individual LEDs are ﬁtted in a graduated arrangement under a transparent glass lens and give off a yellow light when switched on. They appear neutral in colour when switched off.

LED technology offers numerous advantages:

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Operation of the assistant lighting system is described in SSP 288 – Audi A8 ´03 Distributed Functions.

– Rapid attainment of full power – Up to 50 % energy saving as compared to

bulbs – Service life equal to that of the vehicle – Shallow design – Bright, distinct marking effect makes

vehicle more noticeable

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Rear lights

Brake/tail light on side panel – Red LEDs

Brake/tail light on boot lid – Red LEDs

Rear fog light – 16 W HPV bulb

Turn signal indicator – Yellow LEDs

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The newly designed rear lights are an ideal combination of design, function and ultramodern technology.

Light-emitting diodes are used for the tail light, brake light and turn signal indicator functions. Newly developed "High-performance" bulbs are employed for the lesser used rear fog light and reversing light functions. The high-level third brake light also features LEDs.

Interior lighting

Reversing light – 16 W HPV bulb

Reﬂector

Rear light actuation is described in SSP 287 – Audi A8 ´03 Electrical Components.

In addition to the usual interior, reading and door lights, the new Audi A8 also features new "ambiente" and door contour lights with variable functions depending on the lighting proﬁle selected.

Users can choose between the following lighting proﬁles:

– Highway – City – Cockpit – Fond = Rear

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Heating/Air Conditioner

Design and operation

The air conditioning system represents a more advanced version of the concept employed in the Audi A8 predecessor model with 2-zone climate control and features fully automatic regulation.

An optional feature for the Audi A8 ´03 is 4-zone climate control, enabling both driver and all passengers to make individual settings independently of the climate control level selected for the other occupants.

The following components are new features as compared to the systems previously ﬁtted in the Audi A8:

– Humidity sender G355 – Evaporator outﬂow temperature sender

G263 – Two versions: 2-zone front climate control

with 12 control motors and 4-zone front

and rear climate control with 15 control

motors – Rear climate control with electric rear

additional heater as additional equipment

("4-zone system") – rear left and rear right

footwell heater element Z42 and Z43 – Second control and display unit with

4-zone climate control, Climatronic control

unit J255, rear Climatronic control and

display unit E265

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– Climate control menu in MMI (Multimedia

Interface) for display of climate control set values and basic settings

– Front and rear seat heating and seat

ventilation – Heated windscreen Z2 – Energy management control unit J644

The interaction of these components in coordination with the entire air conditioning system forms a control loop and permits comfortable front and rear climate control to suit all requirements.

Heating/Air Conditioner

Operating principle

A distinction is made between two air conditioner unit versions

– 2-zone front and rear climate

control

– 4-zone front and rear climate

control

and three types of control and display unit

– Air conditioner control panel with

no seat heating/ventilation

– Air conditioner control panel with

seat heating

– Air conditioner control panel with

seat heating and seat ventilation

(identiﬁed by part number index).

SSP282_099

Self-diagnosis

Fault diagnosis and measured value blocks for air conditioner and seat heating system can be read out by way of address words 08 "Air conditioner/heater electronics" and 28 "Rear climate control". The functions of and exact procedure for self-diagnosis and assisted fault-ﬁnding with VAS 5051 can be found in the Heating/Air Conditioner Workshop Manual for the relevant vehicle model.

When the ignition is switched on, the Climatronic control unit J255 starts up with the same temperature, air distribution and fresh-air blower speed settings etc. as were applicable the last time the ignition was switched off by way of the appropriate key or using ﬁngerprint recognition. If ﬁngerprint recognition has been implemented, this has priority over key recognition (refer also to SSP 287 – Audi A8 ´03 Electrical Components).

Personalised settings

The following settings can be made for each climate control zone (front left, right and, optionally, with 4-zone climate control rear left and right):

– Left/right temperature – Air ﬂow – Left/right air distribution – Left/right seat heating – Left/right seat ventilation – Operating modes (AUTO for driver and front

passenger, temperature-adjustable centre vents, automatically controlled recirculated-air mode, ECON)

The heated windscreen can be activated by way of the air conditioner defrost button or the air conditioner control unit automatically switches on the electric heated windscreen if the appropriate conditions are satisﬁed (windscreen defrost or automatic mode on cold starting).

The Climatronic J255 and heated windscreen J505 control units communicate by way of the LIN bus. The Climatronic control unit transmits the speciﬁed windscreen heating power to the heated windscreen control unit on the LIN bus.

Key recognition takes place in the case of remote control (radio or key transponder), with the driver identiﬁcation control unit providing the Climatronic control unit J255 with the appropriate information by way of the CAN bus.

The electrically heated windscreen is only supplied with the amount of power which can currently be drawn from the electrical system without draining the battery. This is monitored by the energy management control unit J644.

As is the case with the Audi A4, the windscreen is heated by applying voltage to a metallic foil ﬁtted in the glass (refer to SSP 213).

The Climatronic control unit J255 is connected to the convenience CAN, via which diagnosis is also performed.

A manual air conditioning system is not available.

As in the Audi A4, the air conditioner compressor is regulated as a function of load and controlled externally by way of the compressor regulating valve (refer to SSP 240).

73 74

Climatronic control unit J255

Blower control

Left rotary control/pushbutton

Rotary control +/- for – Temperature – Blower speed – Air distribution up/down – Seat heating – Seat ventilation – Menu control via MMI

Pushbutton – Synchronisation of driver's

side, passenger's side and rear settings

Seat heating control

Driver's side control panel

Seat ventilation control

Air distribution control – Up – Chest vent/centre – Down

Reset to basic setting/ automatic mode

Temperature sensor with blower

Front control panel activation/ deactivation

Heated rear window control

Air conditioner defrost and electrically heated windscreen

Passenger's side control panel

Air conditioner basic setting control

Manual recirculated-air mode control

Rear Climatronic control and display unit E265

Reset to basic setting/ automatic mode

Centre console/footwell air distribution control

Rear right control panel

Rear left control panel

Left rotary control/pushbutton

Rotary control +/- for – Temperature – Chest vent and footwell air

distribution – Seat heating – Seat ventilation

Pushbutton – Synchronisation of driver's

side and passenger's side

settings

Rear left seat heating control

Rear control panel activation/ deactivation

Rear left seat ventilation control

SSP282_100

Rear right seat heating control

Rear right seat ventilation control

Air conditioning system control via MMI

All air conditioning system set values and basic settings (setup) can be displayed by way of the MMI. This applies both to the Climatronic control unit button functions and to setup.

If the air conditioning system is activated with the MMI switched on, the air conditioner function settings can be called up and altered by way of the multimedia control panel. The functions indicated in the corners of the displayed mask are activated using the softkeys.

Basic setting (setup)

The basic air conditioner settings can only be altered when the MMI is active. This involves pressing the SETUP button on the Climatronic control unit.

The following functions can be selected:

– ECON ON/OFF – Automatic air recirculation active/inactive – Synchronisation active/inactive – Centre vent (temperature-adjustable)

settings between - 3 and + 3 – Auxiliary heater active/inactive – Auxiliary ventilation active/inactive – Auxiliary heater/ventilation operating time

15 min./30 min./45 min./60 min. – Auxiliary heater/ventilation timer status for

timers T1, T2, T3 ON/OFF – Solar mode active/inactive (solar cells

C20) – Rear control ON/OFF

Distribution Seat ventilation

AC - driver

21,5° C

low high

Blower Seat heating

SSP282_112

Blower Seat heating

Auto

Distribution Seat ventilation

AC setup

Econ

Autom. air recirculation

Synchron.

Centre vent

Off

SSP282_113

The desired settings can be called up and altered with the driver's/front passenger's control knob on the Climatronic control unit.

The current air conditioner settings are stored automatically and assigned to the appropriate remote control key. On vehicles with Audi one-touch memory (optional), the current setting is also assigned to the corresponding ﬁngerprint.

Heating/Air Conditioner

Blower unit/air routing

As opposed to the predecessor model, the air conditioner features an additional evaporator outﬂow temperature sender G263. This is installed in the air duct downstream of the evaporator and constantly transmits the air temperature downstream of the evaporator to the Climatronic control unit J255.

If the left or right centre chest vent is closed manually, the left/right centre vent control motor V110/V111 is closed automatically by the centre left/centre right G347/G348 vent sensor signal.

When replacing control motors, attention must be paid to the assignment of the ﬂaps in the cam plate guides.

Automatically controlled recirculated air mode

Recirculated air mode is implemented automatically for a certain period

– If the windscreen washer system switch is

actuated or

– In the event of actuation by the air quality

sensor G238

G150 Left vent temperature sender G151 Right vent temperature sender G263 Evaporator outﬂow temperature sender V68 V71 Air-ﬂow ﬂap control motor V102 Centre vent control motor V107 Defroster ﬂap control motor V108 Left footwell ﬂap control motor V109 Right footwell ﬂap control motor

V113 Air-recirculation ﬂap control motor V199 Front right defroster/chest vent

V200 Front left defroster/chest vent

V218 Rear left vent control motor

V219 Rear right vent control motor

Temperature ﬂap control motor

(not illustrated)

shutoff ﬂap control motor

(4-zone system only)

Fresh-air/air-ﬂow ﬂap

Recirculated-air ﬂap

V71

V113

Indirect ventilation/left

Left vent

G150

V107

V200

Defrost ﬂap

G263

Right vent

G151

V199

Indirect ventilation/ right

Right footwell ﬂap

V68

Rear right footwell ﬂap

Left footwell ﬂap

Rear left footwell ﬂap

V108

Centre chest vent temperature/ warm-air ﬂap

Rear left warm-air ﬂap (4-zone system only)

V102

Rear left cold-air ﬂap (4-zone system only)

V219

Cold-air ﬂap/ centre vent

V218

Rear right warm-air ﬂap (4-zone system only)

Rear right cold-air ﬂap (4-zone system only)

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Heating/Air Conditioner

Electric rear additional heater

An electric rear additional heater is ﬁtted under each front seat in the rear climate control footwell air ducts.

Operation

Following a cold start or at low ambient temperatures, there is insufficient waste heat in the coolant to warm the rear of the vehicle by means of a conventional fluid-filled heater. In addition, the drop in temperature in the rear air duct is extremely high in the initial phase.

This problem has been solved by integrating two electric rear additional heaters into the rear footwell air duct. These employ electrical energy from the vehicle electrical system to heat the air supplied to the passenger compartment. In this way, the heating function is available immediately following cold starting.

SSP282_102

A further advantage is that independent temperature regulation (heating) can be provided for the rear footwell with the 4-zone system. A supply of colder air to the rear climate zones as opposed to the front can be achieved by way of the centre chest vents. The temperature can however only be reduced but not increased via these vents through the addition of cold air.

As in the predecessor model, two separately controlled heat exchangers permit the setting of different temperatures at front left/right. All occupants can therefore be provided with individual climate control.

As was the case with the predecessor model, in situ heat exchanger replacement is possible. The procedure involved is described in the current Workshop Manual.

Notes

Heating/Air Conditioner

System layout

Fresh-air intake duct temperature sensor G89

Flap control motor potentiometers G92, G113, G135, G136, G137, G138, G139, G140, G143, G317, G318, G349, G350, G351, G352

Air quality sensor G238

Left/right vent temperature sender G150/G151

Centre vent temperature sender G191

Evaporator outflow temperature sender G263

High-pressure sender G65

Sunlight penetration photosensor G107

Humidity sender G355

Humidity sender heater N340

Solar cells in sunroof C20

Control unit with display in dash panel insert J285

Diagnosis CAN

MOST bus

Front information display and operating unit control unit J523

Front information and display and operating unit control unit J685

Radiator fan control unit J293

Data bus diagnostic interface J533

Sunroof electronics control unit J528

Energy management control unit J644

Rear Climatronic control and display unit E265

Engine control unit J623

Drive system CAN

Radiator fan V7

Air conditioning system compressor regulating valve N280

Flap control motors V68, V71, V102, V107, V108, V109, V110, V111, V113, V199, V200, V220, V218, V219, V221

Climatronic control unit J255

Fresh-air blower control unit J126 with fresh-air blower V2

Convenience CAN

Rear left footwell heater element Z42

Additional heater control unit J364

Rear right footwell heater element Z43

Coolant circulation pump V50

Left/right heat regulation valve N175/N176

Heated windscreen control unit J505

Heated windscreen Z2

Driver seat/front passenger seat ventilation control unit J672/J673

Front left/front right heated seat Z45/Z46

Temperature sender for front left/front right seat G344/G345

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Heating/Air Conditioner

Humidity sender G355

SSP282_104

At low ambient temperatures, when the windscreen is extremely cold, the top third is particularly susceptible to fogging. To cover this area, the humidity sender G355 is ﬁtted in front of the base of the rear view mirror.

The sender is designed to detect the following:

– Humidity level – Sender ambient temperature and – Windscreen temperature

All three functions are combined in the sender housing.

The humidity sender is intended for all equipment versions.

Measurement of humidity level and corresponding temperature

The sender data enable the air conditioning system to detect potential misting of the windscreen in good time. Before water vapour from the air in the passenger compartment can form on the windows, the output of the air conditioner compressor and the blower speed are automatically increased and the defrost ﬂap is opened further. Dry air is then routed from the open defrost vents to the windscreen and side windows via the evaporator and heat exchangers.

Physical principles

Humidity measurement involves determining the water vapour content of the passenger compartment air. The capacity of air to absorb water vapour is governed by the air temperature. It is thus necessary to determine not only the humidity level but also the corresponding air temperature in the measurement area.

The warmer the air, the more water vapour it can absorb. Water starts to condense if this water-vapour enriched air cools down again. This results in ﬁne droplets forming on the windscreen.

Operation

Measurement is performed by way of a special capacitor which can absorb water vapour. The water absorbed produces a change in the electrical properties and thus the capacitance of the capacitor. The capacitance measurement thus provides information on the humidity level. The sender electronics convert the measured capacitance into a voltage signal.

Measurement of windscreen temperature

Physical principles

All bodies exchange heat with their environment in the form of electromagnetic radiation. This electromagnetic radiation can include thermal radiation in the infrared range, visible light or ultraviolet components.

The wavelength of the radiation emitted depends on the temperature of the actual body. A change in the temperature of the body alters, for example, the infrared component of the radiation emitted. The temperature of the body can be determined in a non-contacting manner by measuring the infrared radiation emitted.

Operation

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The infrared radiation emitted by a body (windscreen) is measured by means of a highly sensitive infrared radiation sensor. A change in the temperature of the windscreen also produces a change in the infrared component of the thermal radiation emitted by the windscreen. This is detected by the sensor and converted by the sensor electronics into a voltage signal.

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Heating/Air Conditioner

Climate-controlled seats with heating and ventilation function

The Audi A8 ´03 can be ﬁtted with front and rear climate-controlled seats as optional equipment. These seats offer a combination of seat heating and seat ventilation and can be regulated individually for each occupant.

The buttons for the seat heating and ventilation options are integrated into the front and rear control and display units (refer to Page 74).

Seat heating button

The corresponding feedback LED lights after pushbutton activation of seat heating/seat ventilation. The selected seat heating/seat ventilation stage can be called up in the display segment of the Climatronic control unit J255 and in the MMI (Multimedia Interface) climate control menu. Once seat heating/seat ventilation has been activated, it remains active even after switching off the air conditioner by means of the ON/OFF button.

Under normal circumstances, the seat ventilation function is deactivated automatically after approx. 30 minutes.

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Seat ventilation button

The use of seat ventilation leads to lower occupant skin temperatures. Automatic additional seat heating operation controlled as a function of temperature cancels the cooling effect and the air ﬂow is warmed.

The ventilation function promotes pleasant conditions in the occupant's back and seat area and eliminates sweating more quickly.

Comfort seat

Backrest carbon heating mats

Side bolster carbon heating mat

Air ducts in seat padding

Fan in backrest

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Fan in seat cushion

Seat cushion carbon heating mats

Seat climate control is achieved by way of integrated fans in the seat cushion and backrest. Air ducts in the seat padding convey the air warmed by the seat heating to the occupant through the ﬁne perforations in the leather.

The seat heating and seat ventilation functions are not incorporated into automatic climate control mode.

Heating/Air Conditioner

Block diagram for front air conditioner

Key

C20 Solar cells

G56 Dash panel temperature sensor G65 High-pressure sender G89 Fresh-air intake duct temperature

sensor

G92 Temperature ﬂap control motor

potentiometer G107 Sunlight penetration photosensor G113 Air-ﬂow ﬂap control motor

potentiometer G135 Defrost ﬂap control motor

potentiometer G136 Left central vent control motor

potentiometer G137 Right central vent control motor

potentiometer G138 Central vent control motor

potentiometer G139 Left footwell ﬂap control motor

potentiometer G140 Right footwell ﬂap control motor

potentiometer G143 Air recirculation ﬂap control motor

potentiometer G150 Left vent temperature sender G151 Right vent temperature sender G191 Centre vent temperature sender G238 Air quality sensor G263 Evaporator outﬂow temperature

sender G317 Front right defroster/

chest vent shutoff ﬂap

control motor potentiometer G318 Front left defroster/

chest vent shutoff ﬂap

control motor potentiometer G344 Temperature sender for front left seat G345 Temperature sender for front

right seat G347 Centre left vent sensor G348 Centre right vent sensor G351 Rear left vent warm/cold

control motor potentiometer G352 Rear right vent warm/cold

control motor potentiometer G355 Humidity sender

J126 Fresh-air blower control unit J255 Climatronic control unit J528 Sunroof electronics control unit J533 Data bus diagnostic interface

N175 Left heat regulation valve N176 Right heat regulation valve N280 Air conditioning system compressor

regulating valve

N340 Humidity sender heater

T16 16-pin connector

(diagnostic connection)

V2 Fresh-air blower V42 Temperature sensor blower V50 Coolant circulation pump V68 Temperature ﬂap control motor V71 Air-ﬂow ﬂap control motor V102 Central vent control motor V107 Defroster ﬂap control motor V108 Left footwell ﬂap control motor V109 Right footwell ﬂap control motor V110 Left central vent control motor V111 Right centre vent control motor V113 Air-recirculation ﬂap control motor V199 Front right defroster/chest vent

shutoff ﬂap control motor

V200 Front left defroster/chest vent

shutoff ﬂap control motor

V220 Rear left vent warm/cold ﬂap

control motor

V221 Rear right vent warm/cold ﬂap

control motor

Z42 Rear left footwell heater element Z43 Rear right footwell heater element Z45 Front left heated seat Z46 Front right heated seat

C20

V50 N175 N176

15A

G238 G65 G107 G348 G347

V42 G56

58S

G191

25A

Z43 Z42

25A

J126

Z45 G344 Z46

G345

20A

N340

G355

T16

J533

J528

J255

M M M M M M M M M M M M M

G143

G113 G135

V71V113

G318

Colour code

G317

= Input signal

= Output signal

= Positive supply

= Earth

= Convenience CAN High

G139

G140

G92

V102V68V109V108V199V200V107

in out

G138

V220

G351

G136

Additional signals

Climate control LIN bus for – Heated windscreen control unit J505 – Driver seat ventilation control unit J672 – Front passenger seat ventilation control unit J673

G137

V111V110

V221

= Convenience CAN Low

= LIN bus

G352

10A

G151G263

G150

G89

N280

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Terminal 30/blower

Terminal 30/front seat heating

Input/rear roller blind switch E149

Heating/Air Conditioner

Block diagram for rear air conditioner

G177

Z10

G94

Z11

V271

J674

V273

20A

G178

Z12

G95

J675

E265

20A

V218

G349

V219

G350

G426G427

15A

J533

T16

in out

Z13

V270

Key

E265 Rear Climatronic control and display

V272

unit

G94 Rear left seat temperature sensor G95 Rear right seat temperature sensor G177 Driver side rear seat occupied sensor G178 Front passenger side rear seat

occupied sensor

G349 Positioning motor potentiometer

for rear left vent

G350 Positioning motor potentiometer

for rear right vent

G426 Driver side rear seat

temperature sensor

G427 Passenger side rear seat

temperature sensor

SSP282_115

J533 Data bus diagnostic interface J674 Driver side rear seat ventilation

control unit

J675 Front passenger side rear seat

ventilation control unit

Colour code

= Input signal

= Output signal

= Positive supply

= Earth

= Convenience CAN High

= Convenience CAN Low

T16 16-pin connector

(diagnostic connection)

V218 Rear left vent control

motor

V219 Rear right vent control

motor V270 Rear right seat fan V271 Rear left seat fan V272 Rear right seat backrest fan V273 Rear left seat backrest fan

Z10 Left heated rear seat Z11 Left heated rear seat backrest Z12 Right heated rear seat Z13 Right heated rear seat backrest

= LIN bus

Heating/Air Conditioner

Auxiliary heater/coolant additional heater

An auxiliary heater is available as an option for all vehicle and engine versions. The auxiliary heater with petrol engines and additional heater with diesel engines are integrated into the engine coolant circuit. Vehicles with diesel engine are ﬁtted with an additional heater as standard. On diesel engines with auxiliary heater, the activated auxiliary heater is also used as engine additional heater depending on temperature.

Operation with cut-in by way of remote control or timer

Design and operation are described in

SSP 240 – Audi A2 Technical Features.

The cut-in time is "programmed" by way of the MMI system (Multimedia Interface) under the menu item "timer status".

In the Audi A8 ´03, the auxiliary heater is activated by the air conditioner. The heated coolant is initially supplied to the passenger compartment (primarily auxiliary heater mode). On attaining pre-determined temperature levels, engine pre-heating is then switched in in line with a characteristic curve.

Activation sequence:

1 A remote control or timer signal is

transmitted to the auxiliary heater control unit.

2 The auxiliary heater then transmits a signal

via the CAN bus to the Climatronic control unit J255.

3 The control unit then decides as a function

of desired temperature, ambient temperature and passenger compartment temperature whether auxiliary ventilation or auxiliary heating is to be employed. The setting of the auxiliary heater/ ventilation function is shown in the setup menu in the MMI (Multimedia-Interface).

4.1 Auxiliary ventilation sequence

The energy management control unit J644 interrogates the battery capacity check function of the battery and energy management system to determine whether auxiliary ventilation can be accepted. In the event of acceptance, the fresh-air blower is actuated.

4.2 Auxiliary heating sequence

The level of fuel in the tank is interrogated. If the fuel tank is "empty", the auxiliary heating function is not permitted and the auxiliary heater symbol in the dash panel insert goes out. "Empty" roughly corresponds to the red display zone. The energy management control unit J644 checks whether there is sufﬁcient energy to accept auxiliary heating. If this is the case, the auxiliary heater is switched on in the various operating modes depending on the characteristic temperature curve and the fresh-air blower is actuated. If the auxiliary heating temperature reaches a level of 30 °C, the fresh-air blower is activated and the coolant shutoff valve N279 pulsed in line with the characteristic curve.

The auxiliary heater is switched off automatically on completion of the operating time transmitted by the MMI system to the Climatronic control unit or it can be switched off using the remote control OFF button.

Auxiliary heater circulation pump control

To speed up heating of the passenger compartment and to achieve a better "heat yield" in the air conditioner unit heat exchanger, the circulation pump V55 and coolant shutoff valve N279 are pulsed as a function of water temperature and the heating circuit ﬂow rate is thus reduced.

An electric circulation pump is used for the auxiliary heater. It is not possible to reduce the supply voltage in the auxiliary heater control unit and the circulation pump is thus actuated at speciﬁc intervals to decrease its output.

If the engine is switched off again and not all additional heater criteria (temperature, time) are satisﬁed, the auxiliary heater remains in operation for any residual operating time before being deactivated. This function can be encoded.

Additional control curve for "auxiliary heater" and "additional heater"

When the engine is on, the auxiliary heater and engine temperatures are constantly compared. A switch to the large coolant circuit is made as soon as the engine temperature exceeds the auxiliary heater temperature.

Activation of auxiliary heater circulation pump with engine on (pulsed operation of circulation pump)

In order to be able to ensure a sufﬁcient ﬂow of water through the heat exchanger, the auxiliary heater circulation pump must additionally be switched on, as is the case for instance with the 12-cylinder engine.

Heating/Air Conditioner

Small coolant circuit with auxiliary heater

The small coolant circuit employed with auxiliary heating is designed to ensure rapid warming of the passenger compartment.

With the engine stopped, the coolant shutoff valve N279 switches to the small heating circuit until a deﬁned temperature value has been attained. The coolant exiting from the heat exchangers via the pump/valve unit is conveyed by the circulation pump V55 into the auxiliary heater. After being warmed, the coolant is pumped back into the heat exchangers and initially heats the passenger compartment.

Design and operation are described in

SSP 267 – The 6.0 l W12 engine in the

Audi A8 - Part 1.

Coolant shutoff valve N279

Circulation pump V55

Temperature sender

Auxiliary heater with additional heater control unit J364

Cap

Pump/valve unit with heating-system heat exchangers

Coolant circulation pump V50

Continued coolant circulation pump V51

Non-return valve 2