The 2019 Audi A8 Electrics and Electronics
eSelf-Study Program 970293

Audi of America, LLC
Service Training
Created in the U.S.A.
Created 01/2018
Course Number 970293

©2017 Audi of America, LLC
All rights reserved. Information contained in this manual is based on
the latest information available at the time of printing and is subject to
the copyright and other intellectual property rights of Audi of America,
LLC., its affiliated companies and its licensors. All rights are reserved to
make changes at any time without notice. No part of this document
may be reproduced, stored in a retrieval system, or transmitted in any
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or otherwise, nor may these materials be modified or reposted to other
sites without the prior expressed written permission of the publisher.
All requests for permission to copy and redistribute information should
be referred to Audi of America, LLC.
Always check Technical Bulletins and the latest electronic service repair
literature for information that may supersede any information included
in this booklet.

The eSelf-Study Program (eSSP) teaches a basic understanding of the design and mode of operation of new models, new
automotive components or new technologies.

Note

It is not a repair manual! Figures are given for explanatory purposes only and refer to the data valid at the time of
preparation of the SSP.
For further information about maintenance and repair work, always refer to the current technical literature.

Revision: June 27, 2018
ii

Reference

Introduction

1

Power supply

2

12-volt car battery
Jump start terminal
12-volt supply structure
Fuses and relays
Electrical wiring

48-volt electrical system
General description
Components of the 48-volt electrical system
Design of the 48-volt electrical system
Starter Generator C29
48 Volt Battery A6
Voltage Converter, 48V/12V A7
Working on the 48-volt electrical system
The 48-volt MHEV (Mild Hybrid Electric Vehicle)

Networking
Topology
Bus systems used in the Audi A8

Control modules
Data Bus on Board Diagnostic Interface J533
Vehicle Electrical System Control Module J519 (BCM1)
Windshield wiper and washer system
Comfort System Central Control Module J393 (BCM2)
Rear Lid Control Module J605
Garage Door Opener Control Module J530
Windshield Defogger Control Module J505
Instrument Cluster Control Module J285
Windshield Projection Head Up Display Control Module J898
Door Control Modules J386/J387
Memory Seat/Steering Column Adjustment Control Module J136/J521
Sunroof Control Module J245/J392
Power Adjustable Steering Column Control Module J866
Electronic Steering Column Lock Control Module J764
Steering Column Electronics Control Module J527

Audi drive select
Controllable systems
Driving modes
Displays and operation

Exterior lighting
Operation
Headlights
Matrix beam
Laser lights (S8)
Tail lights

Interior lighting
Background lighting
eSelf-Study Programs

Knowledge assessment

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This eSSP contains video links which you
can use to access interactive media.

iv

Introduction
The fourth generation of the brand flagship is, once again, the
reference point defining the Audi brand – due to a new design
language, an innovative touch concept and the introduction of
mild hybrid technology (MHEV).
The MHEV technology of Audi is based on the newly developed 48 volt electrical system - it supplies the 12 volt electrical system, which in this case is the electrical subsystem. The
48-volt electrical system is powered by a belt alternator
starter (BAS) which is connected to the engine serpentine
drive. A lithium-ion battery, positioned safely under the
luggage compartment floor, serves as an energy storage
device.
Taken together, these measures further improve the already
high fuel efficiency of the engines.

The second component is a lithium-ion battery with a charge
capacity of 10 Ah and a voltage capacity of 48 volts. The newly
developed 48-volt electrical system is the main electrical
system. The 12-volt electrical system is coupled to the main
electrical system via a DC-to-DC converter. The lithium-ion
battery housed in the luggage compartment is about the
same size as a large lead acid battery. A closed-loop air
cooling system provides thermal management.
The 48-volt MHEV technology is particularly unobtrusive and
efficient. When the driver takes his foot off the accelerator at
speed of between 34.1 and 99.4 mph (55 and 160 km/h), the
car can coast for up to 40 seconds with the engine completely
disengaged. The start-stop phase begins at 13.6 mph (22
km/h) when coasting at low speed. For a more complete
description of an MHEV, please refer to page 26.

The mild hybrid drive in the new Audi A8 has two central
building blocks. One of them is the water-cooled belt starter
generator mounted to the end face of the engine. A highperformance poly V belt connects it to the crankshaft. The
belt starter generator has a recuperation capacity of 12 kW
and produces up to 44.25 lb ft (60 Nm) of torque.

48-volt cables with violet-colored insulation

48-volt battery
in the luggage compartment well
664_002

Learning objectives of this eSelf-Study Program:
This eSelf-Study Program describes the electrical and electronic systems of the 2019 A8. When finished, you will be able to:
›› Explain the components of the 48-volt electrical system.
›› Explain the functions and tasks of the Starter Generator C29.
›› List the installation locations and new features of the control modules for the electrical system, networking and comfort/
convenience electronics.

1

Power supply
12-volt car battery
The 12 volt battery of the A8 is located in the right hand
side of the luggage compartment behind a trim panel.
Depending on vehicle equipment, either an EFB1) or AGM
battery2) is used.
Fuse Panel SA and Battery Interrupt Igniter N253 are
attached to the positive battery terminal. If the igniter is
activated, the starter, secondary air pump, and radiator
fans are disconnected from Terminal 30.

Battery Monitoring Control Module J367 is located at the
negative terminal of the 12 volt battery. J367 and the
ground cable form a unit. The term battery data module
(BDM) is sometimes also used for J367. The battery should
only be tested using the VAS Scan Tool via GFF or Guided
Functions. J367 also evaluates the history data of the
battery. As in other Audi models, if the battery is replaced,
it must be adapted using the Scan Tool.

Battery Monitoring Control Module
J367

664_004

Fuse holder
Battery Interrupt Igniter
N253

EFB battery

AGM car battery

An EFB is a heavy duty wet cell battery. The positive plates
are coated with an additional polyester film which provides
the active mass of the battery with additional stability. The
deep cycle resistance of this type of battery is higher than
that of a conventional battery.

With AGM car batteries, the battery electrolyte is absorbed
by a glass microfiber mat. In addition to having higher
deep-cycle resistance, the AGM car battery is noted for its
leak-proof design. This is very important for installation of
the battery inside the car. When charging, it is important to
follow the charger's operating instructions and, if necessary, to set the charger program for AGM car batteries.

The following car batteries are used in the Audi A8 worldwide:
EFB battery

AGM car batteries

69 Ah/360A

68 Ah/380 A

70 Ah/420 A

92 Ah/520 A
105 Ah/580 A

2

1)

Enhanced Flooded Battery

2)

Absorbent Glass Mat

Jump start terminal
The jump start terminal is located in the engine compartment on the right-hand side, between the coolant reservoir
and the plenum chamber.

This connection can also be used for charging both car
batteries in the showroom or for purposes of diagnostic
work in the workshop.

Suppressor
C24

Jump start terminal

Distributor
TV2

Distributor
TV3

664_005

The jump starting terminal is located on the Terminal 30
distributor TV2. It is supplied with voltage via a red 70 mm2
cable from the 12-volt car battery. The Terminal 30 distributor TV3, which has three fuses, is located directly
adjacent to TV2.

The radiator fans, and the secondary air pump are supplied
with voltage through these three fuses. The black 70 mm2
cable connecting to distributor TV2 leads to the 12-volt
starter motor. The interference suppression capacitor C24
is located adjacent to the distributor.

3

12-volt supply structure

J293

J671

TV3

SF

TV2

J299

SE
SC
SB
SA
SR2

J367

SD
SH

N253

SJ

J500

SM
SN
SP

J505
SR3

J1019

664_006

A7
TV1

Key:
A 12-volt battery
A7 Voltage Converter, 48 V/12 V
B Starter
J293 Radiator Fan Control Module
J299 Secondary Air Injection Pump Relay
J367 Battery Monitoring Control Module
J500 Power Steering Control Module
J505 Windshield Defogger Control Module
J671 Radiator Fan Control Module 2
4

J1019
N253
SF
SR2
SR3
TV1
TV2
TV3

Rear Axle Steering Control Module
Battery Interrupt Igniter
Fuse Panel F
Relay and Fuse Panel 2
Relay and Fuse Panel 3
Distributor in luggage compartment, right
Distributor in engine compartment on left
Distributor in engine compartment on right

Fuses and relays
The fuses are identified by the letter "S" and by a number in
the current flow diagram. This also applies to other individual fuses distributed throughout the vehicle.

Distributors TV2 and TV3

The fuses connecting to the relay and fuse holders SR2 and
SR3 as well as the fuses connecting to fuse holder SF are
also accessible to the driver and also described in the
vehicle Owner’s Manual.

Relay and Fuse Panel 1 SR1

Relay and fuse holder SR2 on A pillar
at bottom left. Fuse holders SA, SB,
SC and SE are located here.

Fuse holder at positive terminal of
12-volt battery

Fuse holder SF on left-hand
side of instrument panel

Relay and fuse holder SR3 in
lugagge compartment on left.
Fuse holders SD, SH, SJ, SM, SN
and SP are located here.

664_007

Note
When locating fuse assignments, please refer to the latest current flow diagrams in ElsaPro.

5

Electrical wiring
Main battery lead
Like its predecessor, the Audi A8 has an aluminum main
battery cable. Unlike in the previous model, this is a single-piece cable. It is insulated by a red PVC coating and has a
wire cross-section of 150 mm2. It begins at the positive
terminal of the 12-volt battery as a flexible round conductor.

It continues from the luggage compartment to the righthand side sill as a torsionally rigid flat-section conductor.
Then, as a flexible round-section conductor in the area of
the A pillar, it runs from through the engine bulkhead into
the engine compartment to the distributor TV2.

Copper wires
The A8 electrical system is comprised largely of copper
wires. The range of use extends from 0.13 mm2 wires in the
area of the CAN bus network to 75 mm² wires for power
supply to high-output equipment.
Copper wires with smaller cross-sections can be repaired
with wiring harness repair set VAS 1978 B, while wires with
cross-sections of 10.0 mm² and 16.0 mm² can be repaired
with wiring harness repair set VAS 631 003. Wires with
cross-sections greater than 16.0 mm² have to be replaced if
damaged.

Repairing aluminum wires

Wiring harness repair using the VAS
631003

Reference
For further information refer to eSelf-Study Program 970563 The 2017 A4 Electronic and Electrical Systems.

6

Aluminum wires
Aluminum wires with cross-sections of 2.5 mm2, 4.0 mm2
and 6.0 mm2 are used in addition to the main battery cable.
Unlike the main battery cable, these wires can, if damaged,
be repaired with wiring harness repair set VAS 631 001.

The use of aluminum alloys in certain areas of the vehicle
provides a further reduction in the weight of the wiring
harness. Aluminum wires are not installed in areas where
wires are moved, for example, in the doors, because they
are less flexible than copper wires.

Main battery cable

664_008

7

48-volt electrical system
General description
The 2019 A8 is the first North American Audi model to be
powered by a 48-volt electrical system. It uses a watercooled 48-volt belt starter generator and a 48-volt lithiumion battery. The 48-volt main electrical system also provides the basis for the mild hybrid technology. The Audi A8
is also known commonly as a 48-volt MHEV
(Mild Hybrid Electric Vehicle).

Two new terminal designations were introduced at the
launch of the 48-volt electrical subsystem:
›› Terminal 40 for the 48-volt positive side.
›› Terminal 41 for the 48-volt negative side.

12-volt pinion-type starter

664_060

12-volt cable

8

48-volt cable

48-volt power distributor

48-volt belt starter generator

Components of the 48-volt electrical system
The main components of the 48-volt electrical system are
the belt starter generator and the lithium-ion battery. The
belt starter generator is the power source for the 48-volt
electrical system. If operated as a starter, it has to be
considered a power consumer within the 48-volt system.
The voltage converter is the link between the 48-volt electrical system and the 12-volt electrical system.

The 12-volt electrical system, with its lead acid battery,
supplies all 12-volt power consumers. At the launch of the
Audi A8 these include all control modules as well as the
12-volt pinion-type starter. However, it is only used for
cold-starting the TFSI engine or for starting it for the first
time. All other starting processes are implemented using
the 48-volt belt starter generator.

Circuit diagram
12-volt pinion-type starter

48-volt / 12-volt
converter

12 volts

48 volts

=

12-volt power consumer

48-volt belt starter generator

12-volt battery

=

48-volt battery

48-volt power consumer

664_061

Energy management
Data Bus on Board Diagnostic Interface J533 (gateway)
handles the task of energy management for the 12-volt
electrical system as well as the 48-volt electrical system.
J533 receives information on the status of the 12-volt
battery from Battery Monitoring Control Module J367,
which communicates with J533 via a LIN bus.

The belt starter generator sends information across a
sub-bus system to Engine Control Module J623, which in
turn, communicates with the gateway via the FlexRay bus.
The gateway communicates with the voltage converter and
the 48-volt battery via the hybrid CAN bus.
For a schematic diagram of the 48-volt electrical system
including the 12-volt components relevant to the power
supply, refer to the following double page.