Detection System
Control Module
J706

Engine Control
Module
J623

Airbag
Control Module
J234

Left Front Seat
Belt Tensioner
Control Module
J854
Right Front Seat
Belt Tensioner
Control Module
J855
Climatronic
Control Module
J255

DSG Transmission
Mechatronic
J743

Selector Lever
Sensor System
Control Module
J587

*2.0L TDI engine only
11

Fresh Air Blower
Control Module
J126

Refrigerant Circuit
Pressure Sensor
G805

Humidity Sensor in
Fresh Air Intake
Duct
G657

Air quality sensor
G238

For example, Cornering Lamp and Headlight Range Control
Module J745 would never be installed on the same vehicle
as Headlamp Range Control Module J431.

Headlamp Range
Control Module
J431

Multimedia System
Control Head
E380

Cornering Lamp and
Headlight Range
Control Module
J745

Front Information
Display Control
Head J685

Lane Change
Assistance Control
Module
J769

Digital Sound
System Control
Module
J525

Driver Assistance
Systems Front
Camera
J842
Distance Regulation
Control Module
J428

Information
Electronics Control
Module 1
J794
ABS/ESP
Control Module
J104

Battery Monitoring
Control Module
J367

Power Steering
Control Module
J500

Alternator
C

All Wheel Drive
Control Module
J492

Rearview Camera
System Control
Module
J772

Electronic Damping
Control Module
J250

610_001_pkd

Key:
Powertrain CAN bus

Infotainment CAN bus

LIN bus

Convenience CAN bus

Diagnostics CAN bus

Sub-bus systems

Extended CAN bus

Suspension CAN bus

MOST bus

12

Overview of bus systems
Bus system

Cable color

Configuration

Max. data transfer rate

Characteristic

Powertrain CAN bus

Electrical two-wire bus
system

500 kbit/s

Not single-wire capable

Convenience CAN bus

Electrical two-wire bus
system

500 kbit/s

Not single-wire capable

Extended CAN bus

Electrical two-wire bus
system

500 kbit/s

Not single-wire capable

Infotainment CAN bus

Electrical two-wire bus
system

500 kbit/s

Not single-wire capable

Suspension CAN bus

Electrical two-wire bus
system

500 kbit/s

Not single-wire capable

Diagnostics CAN bus

Electrical two-wire bus
system

500 kbit/s

Not single-wire capable

MOST bus

Optical bus system

150 Mbit/s

Ring structure: an open circuit
leads to total system failure

LIN bus

Electrical single-wire bus
system

20 kbit/s

Single-wire capable

Sub-bus system
(private bus)

Electrical two-wire bus
system

500 kbit/s

Not single-wire capable

New features of the bus system
• The Convenience CAN and Infotainment CAN are highspeed systems on the 2015 A3.
• New MOST bus – MOST150 (MOST150 has replaced
MOST50).
• Instrument Cluster Control Module J285 is a Convenience CAN participant.
• Data Bus On Board Diagnostic Interface J533 is the
master of LIN slave Multifunction Steering Wheel
Control Module J453.
• J533 is not a MOST bus participant.
• Information Electronics Control Module 1 J794 is the
system and diagnostic manager for the MOST 150 bus.
• Information Electronics Control Module 1 J794 is connected to the MMI operating unit and display through a
sub-bus system.

13

Optical data bus system MOST150
History
This data bus system is named after the "Media Oriented
Systems Transport (MOST) Cooperation". This group is
made up of various automobile manufacturers, their components suppliers and software companies, who joined
forces to create a standardized high-speed data transfer
system. It was used for the first time in the 2004 Audi A8.

The term “Media Oriented Systems Transport” denotes a
network that unlike the CAN data bus, sends address oriented messages to specific users. This technology is used
by Audi to transfer data within the Infotainment system.

MOST150
The MOST150 bus is used for the first time by Audi in the
new 2015 A3. It is six times faster than MOST25 and
necessitated some modifications to MOST components.

For instance, the transmitter and receiver units – Fiber
Optical Transmitters (FOT) – had to be adapted. Other
components, such as the optical connectors, the fiber
optics and the electrical connections of the control units,
are identical to those of the MOST25.

Digital Sound
System Control
Module J525

System manager
Two control modules participate on the MOST150 bus in
the 2015 A3:
• Information Electronics Control Module 1 J794
• Digital Sound System Control Module J525
In the 2015 A3, Information Electronics Control Module 1
J794 functions as the system manager and diagnostic
manager for the MOST150 system. The was previously done
by Data Bus On Board Diagnostic Interface J533.

Information
Electronics Control
Module 1 J794

610_069

Special tool VAS 6778
Diagnostics

The ring break diagnosis procedure is identical to that of
the previous MOST bus system. However, the Address Word
for the 2015 A3 is 5F.
Even though the ring break diagnosis procedure remains
unchanged, a new special tool - VAS 6778 - must be used if
there is a DTC in the optical system. This is due to the
increased data transmission speeds.

610_074
14

Control modules
Brief descriptions
Vehicle electrics
Designation

Vehicle Electrical System Control Module J519

Equipment

Always installed

Installation position

Under the left side of the instrument panel

Tasks

•
•
•
•
•
•

Address Word

09

Data bus communication

• Convenience CAN bus participant
• J519 is the LIN master for:
• LIN 1 – Light Switch 1, Wiper Motor Control Module J400, Rain/Light Recognition Sensor G397,
Humidity Sensor G355
• LIN 2 – Alarm Horn H12
• LIN 3 – Power Sunroof Control Module J245, Anti-theft Alarm System Sensor G578

Special feature

LIN 1 is distributed to two pins on J519. J400 is connected to pin B30. E1, G397 and G355 – are connected
to pin C28. This means that the control modules connected to pin C28 are also affected in the event of a
short circuit to positive or negative at pin B30.

Central locking master
Exterior light master
Interior light master
Antitheft alarm master
Activation of various relays
Activation of various convenience components:
• Seat heaters
• Heated windshield washer nozzles
• Windshield washer pump
• Headlight washer system pump
• Reading various switch and button positions
• Reading various sensor values

J519

610_009

Reference
For a detailed description of Vehicle Electrical System Control Module J519, please see eSelf-Study Program 970343, The
2015 Audi A3 Vehicle Electronics and Drivers Assistance Systems.
15

Gateway
Designation

Data Bus On Board Diagnostic Interface J533 (Gateway)

Equipment

Always installed

Installation position

Under the left side of the instrument panel

Tasks

•
•
•
•

Address Word

19

Data bus communication

• All CAN bus system participant
• LIN master of Battery Monitoring Control Module J367 and alternator
• LIN master of multifunction Multifunction Steering Wheel Control Module J453

Special feature

Not a MOST bus user

Networking gateway
Diagnostic master (with the exception of MOST150)
Energy management system control
Master for multifunction steering wheel / optional equipment

J533

610_010

Instrument cluster / DIS
Designation

Instrument Cluster Control Module J285

Equipment

Always installed
Versions:
•
Monochrome DIS with onboard computer, PR No.: 9S5
•
Color DIS with onboard computer, PR No.: 9S6

Installation position

Instrument Panel

Tasks

• Display of information relevant to the driver
• Immobililzer master

Address Word

17

Data bus communication

Convenience CAN bus participant

Special feature

Convenience CAN participant for first time on an Audi model

J285
(European version shown)

610_011

16

Steering column electronics
Designation

Steering Column Electronics Control Module J527

Equipment

Always installed

Installation position

On the steering column

Tasks

• Connects the steering column stock and the electrical components in the steering wheel to the vehicle
electronics
• Terminal management master for vehicles without advanced key

Address Word

16

Data bus communication

Convenience CAN bus participant