Self-Study Programme 459 Audi A8 '10 electrical and network systems.pdf

Self-study Programme 459

Audi A8 ’10

Electrical and network systems

Audi

Service Training

Stability and reliability within the electrical system are an

important basis for system quality in a situation where the number

of electronic systems and components are increasing.

With an overall weight of as much as 50 kilogrammes, around

1,500 individual leads with an average length of approx. 2 metres,

numerous contacts, switches, seals, fuse boxes and wiring ducts,

the electrical system is one of the largest, heaviest and most

expensive parts of a motor vehicle. Nowadays, the electrical

system plays a major role in ensuring the high quality standards

demanded of the electrics/electronics at Audi.

Against the background of present-day energy and environmental

considerations, the development of new, lighter electrical system

components is extremely important, as weight is a major factor in

fuel consumption and, therefore, CO 2 emissions.

The number of electronic control units has grown rapidly in recent

years. Most of today's innovations have only been made possible

by the increasingly higher performance of the electronic systems.

Without that development, many vehicle comforts and

conveniences that are now taken for granted would not have been

achievable.

In comparison with its predecessor, the Audi A8 ’10 features the

following most noticeable differences:

• the number of control units has increased from 68 to 95

• a new bus system, the FlexRay, has increased the number of bus

systems from 6 to 7

• the volume of software on the vehicle now exceeds 230 MB,

which is almost four times the amount on the previous model

459_025

Learning objectives of this Self-study Programme

This Self-study Programme informs you about the network

topology of the Audi A8 ’10. It allows you to quickly and effectively

gain a detailed insight into the electronics on the Audi A8 ’10.

When you have completed this Self-study Programme, you will be

able to answer the following questions:

• In what locations are electrical components fitted on the

vehicle?

• What service-related information should be noted for specific

control units?

• What tasks and functions are performed by the control units on

the vehicle?

• What are the new features of the exterior lights?

Contents

Power supply

Battery _______________________________________________________________________________________________________________________________________________ 4

Jump-starting terminals ___________________________________________________________________________________________________________________________ 5

Main battery lead ___________________________________________________________________________________________________________________________________ 5

Power supply structure _____________________________________________________________________________________________________________________________ 6

Fuses and relays_____________________________________________________________________________________________________________________________________ 7

Network system

Locations of control units __________________________________________________________________________________________________________________________ 8

Network topology _________________________________________________________________________________________________________________________________ 10

New features of bus system _____________________________________________________________________________________________________________________ 12

CAN isolating connector__________________________________________________________________________________________________________________________ 13

FlexRay

Introduction _______________________________________________________________________________________________________________________________________ 14

Comparison between CAN bus and FlexRay ____________________________________________________________________________________________________ 15

FlexRay protocol __________________________________________________________________________________________________________________________________ 16

Design ______________________________________________________________________________________________________________________________________________ 17

Functional procedures ____________________________________________________________________________________________________________________________ 18

Fault diagnosis ____________________________________________________________________________________________________________________________________ 19

Control units

Databus diagnosis interface J533 ______________________________________________________________________________________________________________ 20

Battery monitoring control unit J367 __________________________________________________________________________________________________________ 21

Alternator C _______________________________________________________________________________________________________________________________________ 22

Voltage stabiliser J532 __________________________________________________________________________________________________________________________ 24

Electrical system control unit J519 _____________________________________________________________________________________________________________ 26

Exterior lights

Light switch________________________________________________________________________________________________________________________________________ 28

Headlights _________________________________________________________________________________________________________________________________________ 30

Rear lights _________________________________________________________________________________________________________________________________________ 40

Service

Repairing electronic components using ESD protection ______________________________________________________________________________________ 42

Summary

Self-study Programmes __________________________________________________________________________________________________________________________ 43

• The Self-study Programme conveys a basic knowledge of the design and function of new vehicle models,

new vehicle components or new technologies.

The Self-study Programme is not a repair guide! Any figures quoted merely serve the purpose of

facilitating understanding and relate to the software version valid at the time the SSP was produced.

For details of servicing and repair operations, it is imperative that you refer to the latest technical literature.

Note

Reference

Power supply

Battery

The battery on the Audi A8 ’10 is located in the centre of the spare

wheel recess. Attached to the battery positive terminal is the main

fuse box and the battery isolator.

On the negative terminal is the battery monitoring control unit,

J367. Often referred to as the battery data module (BDM), it is

integral with the earth lead.

Depending on the equipment level on the vehicle, different battery

sizes and types are used to suit the specific vehicle.

All vehicles with Start-Stop system, auxiliary heater or extended

energy recuperation (see page 23) are always fitted with an AGM

battery.

Battery in centre of spare wheel recess

AGM batteries

AGM ( A bsorbent G lass M at) batteries contain a glass microfibre

mat within which the electrolyte is absorbed. They are

distinguished in particular by their spill-proof design, excellent

rechargeability, good cold-starting properties, low self-discharging

rates and zero-maintenance characteristics. For that reason, when

a battery is replaced, not only must the type specified by the

Electronic Parts Catalogue be used but, as with all vehicles that

have an energy management system, it must be learned by (coded

on) the battery monitoring control unit, J367.

Concealed screw joint

for main battery lead in

vicinity of rear seat

The following battery ratings are used on the A8 ’10:

• 95 Ah/450 A

• 110 Ah/520 A

• 92 Ah/520 A (AGM battery)

• 105 Ah/580 A (AGM battery)

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Jump-starting terminals

Main battery lead

The jump-starting terminals are in the engine compartment on the

right-hand side of the vehicle and can also be used for charging the

battery in the showroom or when performing diagnostic checks in

the workshop.

An advanced-design main battery lead is used on the Audi A8 ’10.

Although an aluminium main battery lead has been used before

on the Audi A8 ’03, that was a round-section lead. The Audi A8 ’10

has a rigid, flat-section conductor made of aluminium and covered

with a red plastic insulation layer.

Lead routing

The main battery lead starts at the battery positive terminal as

a flexible, round-section lead. It becomes a rigid, flat-section

conductor before it leaves the spare wheel recess. Apart from its

light weight, this type of main battery lead has other advantages

as well:

• Because of its shape and rigidity, fixings can be dispensed with

• It does not require any cable ducts

• The available space is more efficiently used

• And the 150 mm² cross-section main lead (required on vehicles

with diesel engine) can be routed through the passenger

compartment.

Jump-starting terminals in

engine compartment on R/H side

The lead is made up of two sections which are bolted together on

the heel board (in the vicinity of the rear seat).

Near the right-hand A-pillar, the flat conductor changes back into

a flexible, round-section lead again which, protected by a rubber

grommet, passes through the bulkhead from the passenger

compartment into the engine compartment.

Rubber grommet for passing main

battery lead through bulkhead

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