Bus on Board Diagnostic Interface J533. It prevents unauthorized access to sensitive vehicle data during vehicle
operation.

J533 contains a "White List" which determines which
service is permitted access when the diagnostic firewall
active. As a basic principle, all read services are enabled and
all write services are disabled.
The diagnostic firewall is activated for the first time when
the vehicle has covered a distance of more than 124.2
miles (200 km). This function will be used in other Audi
models at a future date.

Schematic diagram of diagnostic firewall

Diagnostic firewall

Diagnostic
connector

Data Bus on Board Diagnostic
Interface J533

Control unit 1

Control unit 2

Control unit 3

Control unit 4

Control unit 5

Control unit 6

Control unit 7

Control unit 8

664_047

White list:

Disabled services:

››
››
››
››
››
››
››

››
››
››
››

Accessing the diagnostics.
Read event memory.
Read measured data.
Read identication data.
Clear event memory.
Activate / deactivate Transport mode.
All services in the gateway.

Activate control elements.
Carry out basic setting.
Replace control module.
Check SVM control module configuration.

The diagnostic firewall is deactivated

The diagnostic firewall is reactivated

1

When the hood is opened

When the vehicle travels a distance of greater than 12.4 miles
(20 km) with the hood closed

2

If there is no communication with the Vehicle Electrical System
Control Module J519 (BCM1 timeout)

The diagnostic firewall is reactivated when the signals are
present again.

3

When a crash signal is received from
Airbag Control Module J234

The diagnostic firewall is reactivated when transmission of the
crash signal stops

When the diagnostics are accessed with the VAS Scan Tool,
the user is informed that the diagnostic firewall is active.

The status of the diagnostic firewall can be seen via the
Data Bus on Board Diagnostic Interface J533.

The following message appears on the diagnostic tester
display:
Note

The diagnostic firewallis currently active.
It is recommended that the diagnostic fire wall be
deactivated.
Open the hood.
Status of diagnostic firewall:
active
Resume

664_166

41

DoIP - Diagnostics over Internet Protocol
Diagnose via CAN
Because the CAN bus was previously used for vehicle diagnostics, the speed at which the data could be transmitted
across the gateway to the control modules in a vehicle was
limited to a maximum of 1 Mbit/s.

The CAN technology does not allow data to be transferred
at a faster rate than this. This meant that the speed of the
FlexRay (10 Mbit/s) could not be fully utilized for diagnostics or software updates.

Control module
1

Control module
2

Control module
3

Control module
4

Control module
5

Control module
6

Control module
7

Control module
8

Control module
9

FlexRay 10 MBit/s

Diagnostics CAN 1 MBit/s

Extended CAN 500 kbit/s

Comfort/convenience systems CAN 500 kbit/s

664_042

Diagnostics via CAN and DoIP
With the additional Ethernet connection, it is now possible
to utilize the full bandwidth of the FlexRay. This is especially advantageous when parameterizing engine and
transmission control modules. Furthermore, it is now also
possible to parameterise CAN control modules in parallel.
To utilize the Ethernet connection, you must use data
interface VAS 6154, which is equipped with WiFi technology.

The additional wires required for the diagnostic tester
hardware have been installed since the launch of the 2017
Audi Q7 (the first representative of the MLBevo series).
The wires connected to the Data Link Connector have the
same color and cross-section as the FlexRay lines, but serve
as an Ethernet connection.

Control module
1

Control module
2

Control module
3

Control module
4

Control module
5

Control module
6

Control module
7

Control module
8

Control module
9

FlexRay 10 MBit/s

Diagnostics CAN 1 MBit/s

FlexRay 100 MBit/s

Extended CAN 500 kbit/s

Comfort/convenience systems CAN 500 kbit/s

42

664_043

Selective partial network operation
Rationale
The demand for electrical power in the modern automobile
is constantly increasing due to the increasing number of
electronic control modules. To reduce this need for power,
many electrical systems are being configured to operate
according to requirement. That is, they are only utilized
when needed.
Until now, all control modules have been active (awake)
during vehicle operation. The have also participated in bus
communications and consumed electrical power by constantly running in stand-by mode.

Without partial network operation

In the future, it will be possible to group together different
control modules to build various partial networks irrespective of the bus system to which they are connected. The
modules in these partial networks can be activated and
de-activated as required. This saves electrical power. To do
this, the control modules require intelligent transceivers
which do not activate the module until a relevant message
is received.
In the 2019 A8, ten control modules are configured for
partial network operation.

With partial network operation

Gateway

Gateway

664_044

664_045

Key:
Continuous operation
Partial network 1
Partial network 2
Partial network 3
Partial network 4
Partial network 5

43

Frame Detect capability

Control modules in network topologies without selective
partial network operation know only two states.

In networks with partial network operation, selected
control modules are equipped with a transceiver which has
a Frame Detect Mode, that is, the control module can
assume a third state.

›› Bus idle - the control module is also inactive.
›› Data bus active - the control module is running and
consuming electrical power.

Bus idle

›› Data bus active - but the control module is still inactive
because the transceiver has not yet recognized a
wake-up message (i.e. it has not yet detected a data
frame which causes it to wake up the control module).

Frame Detect mode

Data bus active

Without partial network operation

U / volts

U / volts
Micro
Controller

Data bus

Micro
Controller

Data bus

›› Bus communication: Off
›› Transceiver: Sleep mode
›› Control module: "Sleeping"

›› Bus communication: On
›› Transceiver: Active
›› Control module: "Awake"

With partial network operation

U / volts

Data bus

Frame
Detect

Micro
Controller

Data bus

Bus communication: Off
Transceiver: Sleep mode
Frame Detect function: Off
Control module: "Sleeping"

Frame
Detect

Micro
Controller

Data bus

Transceiver:

Transceiver:

››
››
››
››

U / volts

U / volts

››
››
››
››

Bus communication: On
Transceiver: Standby mode
Frame Detect function: On
Control module: "Sleeping"

Frame
Detect

Micro
Controller

Transceiver:

››
››
››
››

Bus communication: On
Transceiver: Active
Wake-up message detected
Control module: "Awake"

Service
Selective partial network operation does not affect vehicle repair procedures. When the diagnostics are accessed, all
control modules are woken up. This facilitates communication between the Scan Tool and the control module.

44

Vehicle Electrical System Control Module J519 (BCM1)
The Vehicle Electrical System Control Module J519 is one of
the central modules whose functions have been expanded
successively in recent years. In addition to typical tasks
such as reading in numerous sensors and activating actuators of the external lighting and wiper control system, a
number of integration functions such as park assist or seat
heater activation are now implemented in J519.

As noted earlier, J519 is now the control module for the
climate control system. All diagnostic functions for the
climate control system are also performed by J519.
It is installed on left hand side of the vehicle under the
instrument panel.

Vehicle Electrical System Control Module
J519

664_101

664_146

45

Brief description

Designation

Vehicle Electrical System Control Module J519 /
also referred to as BCM1 (Body Control Module 1)

Equipment

Always installed

Installation location

Below the instrument panel on the left-hand side of the vehicle
(installation location is always on the L/H side, even in RHD models)

Tasks

Exterior lighting master
Interior lighting master
Diagnostic gateway for the light control modules
Interface for various connect services
Integration functions
›› Parking
• Parking aid
• Park assist steering
›› Background lighting
• Activation of the interior light modules
›› Climate control

46

Address Word

0009

Data bus communication

›› Comfort/convenience systems CAN 2 user
›› J519 is the LIN master for
• LIN 1: Light Switch E1, Rain/Light Recognition Sensor G397 and Humidity Sensor G355,
Wiper Motor Control Module J400, Windshield Washer Pump Control Module J1100
• LIN 2: Garage Door Opener Control Module J530, Automatic Dimming Interior Rearview
Mirror Y7, Roof Electronics Control Module J528, Rear Interior Lamp WX2
• LIN 3: Power Adjustable Steering Column Control Module J866, Driver Seat Backrest
Blower Fan V388, Driver Seat Cushion Blower Fan V390, Front Passenger Seat Backrest
Blower Fan V389, Front Passenger Seat Cushion Blower Fan V391
• LIN 4: Switch Module in Instrument Panel, Center EX22, Center Console Switch Module
1 EX23
• LIN 5: Interior light modules 1 - 15
• LIN 6: Interior light modules 16 - 30
• LIN 7: Interior light modules 31 - 45
• LIN 8: Heating control (4 pcs), Left Rear Backrest Fan 1 1 V520, Left Rear Seat Cushion
Fan 1 V522, Right Rear Backrest Fan 1 V524, Right Rear Seat Cushion Fan 1 V526, Rear
A/C Display Control Head E265
• LIN 9: Servomotors (15 pcs)
• LIN 10: Fresh Air Blower Control Module J126, Exterior Air Quality and Humidity Sensor
G935, flap positioner (2 pcs), Air Ionization System Control Module J897, Vehicle Interior Carbon Dioxide Concentration Sensor G929, Air Freshening System Control Module
J1101
• LIN 11: High Pressure Sensor G65, Low Pressure Side A/C Pressure/Temperature Sensor
G1052, High Pressure Side A/C Pressure/Temperature Sensor G1053, servomotors (LIN
series, 5 pcs)
• LIN 12: Rear Fresh Air Blower Control Module J391, servomotors (7 pcs), Front A/C
Display Control Head 1 E774, Front A/C Display Control Head 2 E775, Front A/C Display
Control Head 3 E776, Front A/C Display Control Head 4 E777, Front A/C Display Control
Head 5 E778, Front A/C Display Control Head 6 E884
›› Communicates via a sub-bus system with the Left and Right LED Headlamp Power Output
Modules 1 A27 and A31, Left Light Control Module J1018 and 1023 and the Driver Assistance Systems Control Module J1121

Special feature

The interior light modules of the background lighting and the AC servomotors can be connected to the relevant LIN branch both as LIN series and in parallel. This possibility must be
considered during troubleshooting. Always refer to the current flow diagram applicable to the
vehicle’s equipment specification.

Illuminated seat belt buckle (optional, PR no. 6C5)
General description
The 2019 A8 is optionally available with illuminated seat
belt buckles. Illuminated seat belt buckles help the vehicle
occupants to locate their seat belt buckle in the dark. The
illuminated seat belt buckles are installed at the front and
rear on the driver and front passenger sides. The Vehicle
Electrical System Control Module J519 is, in its capacity as
the "interior light manager", responsible for illumination.

The actual seat belt function is unchanged. Each seat belt
buckle has a switch for seatbelt fastening detection. A
2-pin connector is sufficient for this purpose. The illuminated seat belt buckles are additionally equipped with two
LEDs. These seat belt buckles have a 5-pin connector with
four assigned pins. The two wires for the switches of the
seatbelt fastening detection function are conneceted to the
Airbag Control Module J234. The other two wires are
required for activating the LEDs. The LEDs illuminated an
optical fiber which, in turn, illuminates the area around the
seat belt button.
Area illuminated by
optical fiber

Electronics with
2 LEDs

Airbag Control Module
J234

1
2
3
4

664_162

Terminal 31

Activation of the lighting
The LEDs for the illuminated seat belt buckles are connected to terminal 58xt, which is activated by the Vehicle
Electrical System Control Module J519. Terminal 58xt is the
switch search lighting.
This means that J519 activates terminal 58xt when the
vehicle is unlocked and if a door is opened after the vehicle
has been unlocked. This switches on the interior light as
well as the lighting of key controls, such as the start-stop
button, and the illuminated seat belt buckle. This lighting
is switched off again after a certain time by the interior
lighting run-on function.

Terminal 58xt
Vehicle Electrical System
Control Module
J519

47

Automatic Dimming Interior Rearview Mirror Y7
The rear-view mirror and exterior door mirrors door mirrors
are dimmed automatically when incident light is detected
from the rear (for example, headlights of a following
vehicle).

The light sensor is located at the top center behind the
glass surface of the rear-view mirror (not visible to the
driver).

Features of the automatic dimming mirrors:
›› "Frameless look" mirror housing with concealed edges;
chrome accents are optional.

›› The electronics for dimming the rear-view mirror also
control the dimming of the door mirrors.

›› Mirror is preconfigured for compass display, for the high
beam assist electronics and for the camera systems of
various assistance systems.

›› Y7 is an integral part of the rear-view mirror module
EX5.