Audi Q5 4 User Manual

Service Training

The Audi Headlight Assist System

Self-Study Programme 434

Introduction

With the Headlight Assist System, AUDI has added a new highlight to its range of driver assist systems. The
system enhances ride comfort in the dark by automatically switching the main-beam headlights on or off
depending on the momentary traffic situation. Thus, it provides improved visibility while driving at night.

Surveys have shown that many drivers forgo switching on their main-beam headlights at night, even though
this would greatly improve visibility, and therefore safety, during night-time driving. Respondents cited, as
reasons, that under no circumstances do they want to dazzle oncoming traffic, or that they are familiar with
the route and therefore do not feel the need to use the main-beam headlights, or that they cannot be bothered
switching the main-beam headlights on and off all the time due to heavy oncoming traffic.

However, the visibility of objects is greatly reduced while driving with the headlights dipped, as opposed to
driving with the headlights on main beam. When driving with the headlights on main beam, objects can often
be detected well enough in advance for the driver to stop in time or take evasive action.

The Headlight Assist System maximises the "on" time of the main-beam headlights in the dark, and only dims
down when the ambient and traffic conditions necessitate. The main-beam headlights are dipped before they
can dazzle another road user. The driver has all the advantages of better-illuminated surroundings, without
having to constantly switch the main-beam headlights on and off by himself.

434_033

Contents

Function description

The function of the Headlight Assist System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

On and off conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Mode of operation of the Headlight Assist System

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

An oncoming vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

A vehicle ahead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Driving through a built-up area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

A built-up area at a distance from the road . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

A single house by the roadside. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

System operation and displays

System operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

The operating logic of the Headlight Assist System . . . . . . . . . . . . . . . . . . . . . . . 13

Displays in the dash panel insert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Functional implementation in the vehicle

Component parts of the Headlight Assist System . . . . . . . . . . . . . . . . . . . . . . . . 15

The electrical interface of the rear-view mirror . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

The distributed "Headlight Assist" function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Communication structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Diagnostics

Diagnostics in the Headlight Assist control unit J844 . . . . . . . . . . . . . . . . . . . . . 20

Diagnostics in the onboard power supply control unit J519 . . . . . . . . . . . . . . . 22

The Self-Study Programme teaches the design and function of new vehicle models,
new automotive components or new technologies.

The Self-Study Programme is not a Repair Manual.
The values given are for illustration purposes only and refer to the software version valid at the time of prepa­ration of the SSP.

For information about maintenance and repair work, always refer to the current technical literature.

NoteReference

Function description

The function of the Headlight Assist System

The Headlight Assist System is a new driver assist
system by AUDI. In future it will be available as
optional equipment throughout the model range.
The system provides the driver with better visibility
in the dark because the main-beam headlights
remain "on" as long as the traffic and ambient con­ditions allow.

When the camera of the Headlight Assist System
detects an oncoming vehicle or a vehicle ahead, the
headlights are dimmed down in order to avoid daz­zling other road users. If the detected vehicles are
again outside the range of the Headlight Assist Sys­tem, the headlights automatically dim up again.

The Headlight Assist System also detects built-up
areas and towns from the street lighting, where­upon the system dims the headlights down again.
After leaving a built-up area or town, the headlights
automatically dim up again. The system software is
also able to detect dense fog, and when it does it
also dims the headlights down.

The Headlight Assist System will initially be availa­ble only in combination with xenon headlights.

434_002

The Headlight Assist System maximises the "on"
time of the main-beam headlights and thereby pro­vides better visibility. The driver has less workload
and is able to concentrate better on the traffic.

434_003

The system will, however, also be available in combi­nation with halogen headlights at a later date.

Note

The Headlight Assist System is a driver assist system which aids the
driver in the dark by automatically switching the main-beam headlights
on and off. However, it does not discharge the driver from his duty to
make responsible use of the main-beam headlights while driving. For this
reason, the driver can turn the main-beam headlights on and off manually
at any time, even when they are on.

4

On and off conditions

Switching on of the main-beam headlights by the Headlight Assist System:

To make use of the Headlight Assist System, the system must first be activated by the driver by flicking the
main-beam stalk forward. The Headlight Assist System can only be activated when the rotary light switch is
in the "Auto" position.

The activated Headlight Assist System switches on the main-beam headlights only if all the following condi­tions are met:

• The camera of the Headlight Assist System indicates that the ambient luminosity has dropped below a pre­configured threshold value

and

• The dipped headlights have already been switched "on" at the instruction of the rain and light detector sen­sor

and

• The vehicle is travelling at a speed of greater than 60 kph

and

• Neither a vehicle ahead nor an oncoming vehicle or motorcycle has been detected

and

• No built-up area has been detected

Switching off of the main-beam headlights by the Headlight Assist System:

If the main-beam headlights have been switched on by the Headlight Assist System, they will be switched off
again under the following conditions:

• An oncoming vehicle or motorcycle has been detected

or

• A vehicle ahead or motorcycle has been detected

or

• A sufficiently illuminated built-up area has been detected

or

• The vehicle's speed drops below 30 kph

or

• The Headlight Assist System clearly detects fog

Note

The Headlight Assist System will be available in various AUDI models. The
specifications given in this Self-Study Programme refer to the A4 and A5
models. Though the Headlight Assist System does not fundamentally dif­fer from model to model, system specifications for other models may vary
slightly from those for the A4 or A5.

5

Mode of operation of the Headlight Assist System

Introduction

The following illustrations, which show the mode of
operation of the Headlight Assist System in miscel­laneous traffic situations, are not true to scale. They
are schematic diagrams which are intended to pro­vide an insight into the basic mode of operation of
the Headlight Assist System.

Max. 1000 m

Exact dim-up times or dim-down times cannot be
extrapolated from these diagrams. These timings
depend on several factors, such as the visibility con­ditions, the nature of the road and the luminous
power of the headlights of oncoming vehicles or
traffic ahead.

Range of the Headlight

Assist System

The following illustrations show the range of the
Headlight Assist System, which can extend to 1000 m.
It should be noted that this is the maximum range
and is only achievable in optimum conditions. In real­life traffic situations, however, the actual range will
be below this value.

434_004

A more exact value cannot be given because it heavily
depends on the momentary ambient conditions, such
as visibility, the nature of the road and the type of sur­roundings.

6

An oncoming vehicle

434_005

The oncoming vehicle is still outside the range of the
Headlight Assist System.

434_007 434_008

The oncoming vehicle is now so close that the Head­light Assist System dims down in order to avoid daz­zling the approaching driver.

434_006

The oncoming vehicle is within the range of the Head­light Assist System. However, the vehicle is still far
enough away, so the Headlight Assist System does
not dim down yet.

The Headlight Assist System has not detected the
oncoming vehicle for over 1 second. For this reason,
the main-beam headlights are switched on again.

7

Mode of operation of the Headlight Assist System

A vehicle ahead

434_009 434_010

The vehicle ahead is still outside the range of the
Headlight Assist System.

434_011 434_012

The vehicle ahead is now so close that the Headlight
Assist System has dimmed down.

The vehicle ahead is within the range of the Head­light Assist System. However, the vehicle is still far
enough away, so the Headlight Assist System leaves
the main-beam headlights switched "on".

The vehicle ahead is being overtaken. Because the
Headlight Assist System still detects the taillights of
the other vehicle during the last 3 seconds of the
overtaking manoeuvre, the dipped headlights
remain switched "on" for the time being.

The taillights of the vehicle that has been overtaken
have not been detected for more than 3 seconds. For
this reason, the main-beam headlights are switched
on again.

8

434_013 434_014

The overtaking manoeuvre has been completed and
the vehicle with Headlight Assist continues driving
with the main-beam headlights on.

Driving through a built-up area

434_015 434_016

The built-up area is still outside the range of the
Headlight Assist System. For this reason, the Head­light Assist System has switched on the main-beam
headlights.

434_017 434_018

Because a sufficiently illuminated built-up area has
been detected, the main-beam headlights are
switched off.

The built-up area is now within the range of the
Headlight Assist System. The main-beam headlights
are still switched on.

The vehicle has passed through the built-up area
and the Headlight Assist System detects no further
light sources within its range. For this reason, the
main-beam headlights are switched on again.

Note

Light sources in a built-up area identified as such
by the Headlight Assist System are required to
have a minimum luminous intensity. For example,
roadside street lamps meet this condition.

9

Mode of operation of the Headlight Assist System

A built-up area at a distance from the road

434_019 434_020

The built-up area, located at a distance from the
road, is still outside the range of the Headlight Assist
System. The main-beam headlights are switched on.

434_021 434_022

The system determines that the built-up area is not
sufficiently illuminated. Because the vehicle is travel­ling faster than 90 kph, the main-beam headlights
remain switched on.
Had the vehicle been travelling at less than 90 kph,
the main-beam headlights would have been switched
off.
The 90 kph speed threshold is another threshold rele­vant to the Headlight Assist System. However, it is
only applied in this specific case.

The built-up area is now within the range of the
Headlight Assist System. The main-beam headlights
remain switched on.

The built-up area is no longer within the range of
the Headlight Assist System. The main-beam head­lights remain switched on.

10

A single house by the roadside

434_023 434_024

The house and the street lamp are still outside the
range of the Headlight Assist System. The main­beam headlights are switched on.

434_025 434_026

Because only a single light source is detected, the
main-beam headlights remain switched on.

The house and the street lamp are now within the
range of the Headlight Assist System. The main­beam headlights remain switched on.

The house and the street lamp are again outside the
range of the Headlight Assist System. The main­beam headlights remain switched on.

11

System operation and displays

System operation

Activating the Headlight Assist System:

To activate the Headlight Assist System, the rotary
light switch must be in the "AUTO" position. The
Headlight Assist System can be activated by flicking
the main-beam stalk forward.
The Headlight Assist System must be reactivated
during each terminal 15 cycle.

flick forward

"stalk not actuated" position

Deactivating the Headlight Assist System:

The Headlight Assist System is permanently deacti­vated when the rotary light switch is moved out of
the "AUTO" position. Flicking the main-beam stalk
forward deactivates the Headlight Assist System
until the main-beam stalk is flicked forward again.

pull back

Overriding the Headlight Assist System:

The driver can override any decision made by the
activated Headlight Assist System (main-beam
headlights on or off) at any time.

Main-beam headlights switched on by the Headlight
Assist System can be switched off by pulling the
main-beam stalk back. This also deactivates the
Headlight Assist System.

If the Headlight Assist System has switched on only
the dipped headlights, the main-beam headlights
can be switched on by flicking the main-beam stalk
forward. This also deactivates Headlight Assist Sys­tem.

434_027

New features of the indicator and main-beam stalk:

On introduction of the Headlight Assist System, the
relevant models will be equipped with a modified
indicator and main-beam stalk. The new main-beam
stalk no longer engages in its end position when it
is pushed forward, but returns to its initial position
after it is released. The software of the steering col­umn electronics J527 monitors when the main­beam stalk is flicked forward and pulled back, and
processes the information accordingly.

12

The operating logic of the Headlight Assist System

Activation and deactivation of the Headlight Assist System, overriding of the Headlight Assist System by the
driver, manual switching on and off of the main-beam headlights and actuation of the headlight flasher can
be controlled in two ways by using the main-beam stalk:

• By flicking the main-beam stalk forward

and

• By pulling the main-beam stalk back

To implement all these functions with only 2 means of operation, the software of the onboard power supply
control unit J519 incorporates an operating logic. The operating logic can be represented in the form of a sta­tus diagram with 4 principal states:

• Headlight Assist System (HAS) deactivated and main-beam headlights "off"

• Headlight Assist System (HAS) deactivated and main-beam headlights "on"

• Headlight Assist System (HAS) activated and main-beam headlights "off"

• Headlight Assist System (HAS) activated and main-beam headlights "on"

Ter m in a l 1 5 "on "

and rotary light switch

set to AUTO

Main-beam headlights

"off"

HAS deactivated

flick

flick

forward

forward

(dipped
head­lights
"off")

Main-beam headlights

"off"

HAS activated

Operating logic of the Headlight Assist System (HAS)

pull back

relea se

"

d

n

r

o

a

"

w

s

r

t

o

h

f

g

k

i

l

c

i

d

l

f

a

e

h

d

e

p

p

i

d

(

situation-dependent

pull back

Headlight flasher

pull back

)

(automatic)

Headlight flasher

Main-beam headlights

"on"

HAS deactivated

flick

forward

p

u

l

l

b

a

c

k

flick
forward

Main-beam headlights

"on"

HAS activated

relea se

434_028

13

System operation and displays

Displays in the dash panel insert

Warning lamp in the dash panel insert

When the Headlight Assist System is active, this is
indicated in the dash panel insert in the position at
which total mileage (km) is otherwise displayed
when Headlight Assist is deactivated.

If the main-beam headlights are "on", the familiar
blue main-beam headlight warning lamp in the dash
panel insert will be lit. This lamp comes on regard­less of whether the main-beam headlights have
been switched on manually or by the Headlight
Assist System.

Fault texts in the dash panel insert

434_029

• Fault message "System malfunction"

If the Headlight Assist System is no longer available
to the customer due to a fault, this is indicated to
the driver by the fault message shown adjacent,
which appears in the centre display of the dash
panel insert.

• Fault message "Please wash windscreen"

If the software of the Headlight Assist System estab­lishes that the visibility of the camera is impaired,
the fault message shown adjacent instructs cus­tomer to wash the windscreen or to remove ice,
road tax discs or stickers.

Headlight

Assist:

System

malfunction

434_030

Headlight

Assist:

Please

wash

windscreen

434_031

Note

The camera lens is located
within the wiping field of the windscreen wiper

14

Functional implementation in the vehicle

Component parts of the Headlight Assist System

The electronics and optics of the Headlight Assist
System are wholly integrated in the rear-view mirror.
The camera of the Headlight Assist System is built
into the base of the rear-view mirror, which is
securely attached to the windscreen. The camera is
a special black-and-white camera.

The Headlight Assist control unit J844, on the other
hand, is located in the actual rear-view mirror, which
is mounted movably. The Headlight Assist control
unit is an Extended-CAN user and exchanges infor­mation with other control units via this bus.

Headlight Assist System camera

Rear-view mirror / vehicle electronics

8-pin connector

Headlight Assist

camera

434_032

PCB accommodating the hardware
of the Headlight Assist
control unit J844

Sensor of compass in rear-view mirror

434_033

15

Functional implementation in the vehicle

The electrical interface of the rear-view mirror

The rear-view mirror has an 8-pin connector, which
connects the Headlight Assist control unit J844, the
electronics of the automatic mirror-dimming func­tion and the humidity sender G355 to other vehicle
electronics.

The Headlight Assist control unit J844 and the elec­tronics of the automatic mirror-dimming function
are mounted on a common PCB. The two EC lines
are required to implement the automatic mirror­dimming function. They provide for dimming down
of the two exterior mirrors. A discrete line indicates
to the function whether the interior light has just
been switched on or off.

Mirror base

Headlight Assist

camera

The Headlight Assist System exchanges information
with other in-vehicle control units via 2 Extended­CAN lines. The automatic mirror-dimming function
receives via the CAN bus information on whether
the reversing light is currently switched on or off.
The electronics in the rear-view mirror receive their
voltage supply via a terminal 15 line and a terminal
31 line.

The humidity sender G355 still requires an addi­tional LIN bus line in order to communicate with the
convenience system central control unit J393, its
LIN master. If the vehicle is equipped with a single­zone air conditioning system, the humidity sender
(and hence the LIN bus line) is not installed.

to the exterior mirror

EC = electrochromatic

Headlight Assist control
unit J844 and automatic

mirror dimming function

EC -

EC +

Termin a l 1 5

Termin a l 3 1

Extended-CAN low

Interior light signal

Extended-CAN high

Humidity

sensor

G355

Rear-view mirror

LIN bus

434_034

16

The distributed "Headlight Assist" function

The Headlight Assist function is distributed among
the Headlight Assist control unit J844 and the
onboard power supply control unit J519 . The Head­light Assist control unit J844 determines from the
camera image the current ambient conditions and
the traffic situation ahead of the vehicle. The Head­light Assist control unit receives via the CAN bus
information on the vehicle's current speed and the
instruction of the rain and light detector sensor to
switch the dipped headlights on or off. Depending
on this information, the Headlight Assist control
unit sends to the onboard power supply control unit
J519 a recommendation to switch the main-beam
headlights on or off.

The onboard power supply control unit J519 imple­ments the operating logic in its software. When the
headlight control stalk is moved forward or back,
the onboard power supply control unit J519 calcu­lates the next state depending on the current state
(main-beam headlights on or off; Headlight Assist
activated or deactivated). Depending on the next
state, the onboard power supply control unit acti­vates or deactivates the Headlight Assist System or
switches the main-beam headlights on or off.

The onboard power supply control unit also utilises
CAN messages to control status displays and fault
texts belonging to the Headlight Assist function in
the dash panel insert.

On vehicles fitted with xenon headlights, the main­beam headlights are switched on by activating the
two dipped headlight shutters V294 and V295. In
this case, the dipped and main beams on each side
of the vehicle are realised by a single gas discharge
lamp only.

On vehicles equipped with halogen headlights, the
dipped and main beams are separate. Accordingly,
the onboard power supply control unit activates
the two main-beam headlights M30 and M32
directly in order to switch on the main beam.

Headlight Assist control unit J844

Diagnostics of

the Headlight

Image

processing

Assist System

Link to other

vehicle

variables

Monitoring of

traffic

situation

Measurement

of ambient

brightness

Recommendation: "Main-beam headlights on or off"

Onboard power supply control unit J519

Activates

status indication

in dash panel

Implementation

of operating

logic

insert

Headlight

Assist camera

Activates

fault texts in

dash panel

insert

Activation of

main-beam

headlight

434_035

17

Functional implementation in the vehicle

Communication structure

The following diagram summarises all the control
units incorporated in the Audi Headlight Assist
function. It also shows the various bus systems via
which the control units communicate with each
other.

Headlight Assist

control unit

J844

Extended

-CAN

ABS

control unit

J104

Data bus diagnostic

interface

J533

This communication structure applies to the A4 and
A5 models. A different communication structure
may apply to other models.

Main-beam stalk

Steering column

electronics

control unit J527

Convenience CAN

Onboard power

supply control unit

J519

discrete

LIN bus

Light switch

E1

Dash panel

insert/running gear CAN

Control unit in

dash panel insert

J285

Headlight Assist control unit J844:

The Headlight Assist control unit J844 sends to the
onboard power supply control unit J519 a recom­mendation to switch the main-beam headlights on
or off depending on the current vehicle, traffic and
ambient conditions. The current traffic and ambient
conditions are determined from the images pro­duced by the Headlight Assist camera.

Term i n a l 5 6 a

Xenon headlights

Dipped headlight

shutter,

left V294

Term i n a l 5 6 a

Xenon headlights

Dipped headlight
shutter, right V295

Onboard power supply control unit J519:

The onboard power supply control unit J519 indi­cates to the dash panel insert control unit J285
whether the warning lamp of the main-beam head­lights and the Headlight Assist System have to be
activated or not. If necessary, onboard power supply
control unit also instructs fault texts to be displayed
in the centre display of the dash panel insert.

Rain and light

detector

sensor G397

434_036

18

Data bus diagnostic interface J533:

Steering column electronics control unit J527:

The data bus diagnostic interface J533 serves the
exchange of messages between various CAN data
bus systems. The accessibility of the Headlight
Assist control unit J844 and the operability of indi­vidual bus systems can also be checked for diagnos­tic purposes.

ABS control unit J104:

The ABS control unit J104 keeps the Headlight
Assist control unit J844 continuously informed of
the current vehicle speed. This information is
required because the Headlight Assist System has
to take various speed thresholds into account. The
Headlight Assist System also receives from control
unit J104 the yaw rate, which is required
for auto-calibration of the Headlight Assist function.

Control unit with display in dash panel insert J285

The control unit with display in dash panel insert
J285 receives from the onboard power supply con­trol unit J519 the information as to whether the
Headlight Assist System is currently activated or
not. Accordingly, the Headlight Assist status indica­tor lamp in the dash panel insert is switched on or
off. When a fault occurs, the customer is also
informed by means of fault texts. The control unit
with display in dash panel insert J285 also receives
this information from the onboard power supply
control unit J519.

The steering column electronics control unit J527
indicates to the onboard power supply control unit
J519 whether the main-beam stalk has been moved
forward or back. The operating logic in the onboard
power supply control unit requires this information.

Rotary light switch E1:

The rotary light switch E1 indicates to the onboard
power supply control unit the current position of
the rotary light switch. The Headlight Assist can
only be activated in the AUTO position.

Rain and light detector sensor G397:

The rain and light detector sensor G397 instructs
the onboard power supply control unit J519 to
switch the dipped headlights or on off, due to the
momentary ambient conditions. The Headlight
Assist System can only the activate or deactivate
main-beam headlights if the dipped headlights are
currently "on" at the instruction of the rain and light
detector sensor.

19

Diagnostics

Diagnostic tasks in the Headlight Assist control unit J844

The Headlight Assist control unit J844 is a self-diagnosable control unit which is addressed by the diagnostic
tester using address word 20.

434_037

• Data blocks

The following information can be extracted from the data blocks of the Headlight Assist System:

– Headlight Assist ready yes / no
– Dimming up recommended by Headlight Assist yes / no
– Headlight Assist camera: unimpaired visibility yes / no
– CAN messages received from convenience system control unit J393 yes / no
– CAN messages received from data bus diagnostic interface yes / no
– CAN messages received from ABS control unit yes / no
– CAN messages received from steering column electronics control unit J527 yes / no

Other data blocks display information about the "Auto dimming rear view mirror" function and about the com­pass function in the rear-view mirror.

•Encoding

The control unit receives the following encoding information for the Headlight Assist System:

– Headlight type
– Left-hand drive or right-hand drive
– Vertical offset (model-dependent windscreen inclination angle)
– Windscreen transmissivity (translucency of the windscreen; windscreen type)

20

• Adaption channels

The Headlight Assist control unit contains the following adaptions:

– Vehicle is a left-hand drive / right-hand drive model

• Final control diagnostics

– The Headlight Assist control unit sends to the onboard power supply control unit J519 the recommenda-

tion to switch on the main-beam headlight. It sends the recommendation regardless of the current traffic
and ambient conditions, as well as other relevant vehicle variables.

To switch on the main-beam headlight, the rotary light switch must be in the "AUTO" position so that the
dipped headlights can be switched on and the Headlight Assist function activated.

In addition, the Headlight Assist System provides the following independent final control diagnoses:

– Dim down rear-view mirror (and exterior mirrors, if fitted)
– Activate all segments of compass in rear-view mirror (if fitted)

• Fault memory entries

The following fault memory entries are possible in the Headlight Assist control unit J844:

– Control unit - electrical fault
– Control unit - faulty
– Control unit - not encoded
– Function deactivation due overtemperature in control unit
– Headlight Assist control unit - impaired visibility
– Headlight Assist control unit - decalibrated
– Supply voltage outside allowable range
– Function impairment due to undervoltage
– Function impairment due to overvoltage
– No communication with the data bus diagnostic interface J533
– No communication with the ABS control unit J104
– No communication with the convenience system central control unit J393
– No communication with the onboard power supply control unit J519
– No communication with the steering column electronics control unit J527
– Extended-CAN – no communication
– Function impairment due to implausible message
– Function impairment due to received error value

Calibration

The Headlight Assist System does not require calibration using special tools. The system carries out auto-cali­bration continuously, whereby correction parameters are determined. These parameters are taken into
account during image processing.

21

Diagnostics

Diagnostics in the onboard power supply control unit J519

• Data blocks

The following information can be extracted from the data blocks of the onboard power supply control unit
J519:

– Headlight Assist ready yes / no
– Dimming up recommended by Headlight Assist yes / no
– Headlight Assist control unit faulty
– Headlight Assist camera: unimpaired visibility yes / no
– Dash panel insert should switch on Headlight Assist warning lamp yes / no
– Message text

"Headlight Assist: System malfunction"
"Headlight Assist: Please wash windscreen"

is currently indicated in the dash panel insert yes / no

•Encoding

The control unit receives the following encoding information for the Headlight Assist System:

– Headlight Assist installed / not installed

• Fault memory entries

The following fault memory entries are possible in the onboard power supply control unit J519:

– No communication with the Headlight Assist control unit J844
– Headlight Assist control unit J844 faulty – Please read out fault memory J844

22

Test yourself

Which of the following answers is correct?
Sometimes only one answer is correct.
At other times, more than one answer may be correct – or all of them!

1. Which circumstances cause the main-beam headlights to be switched off by the Headlight
Assist System?

A) When the system detects a pedestrian
B) When the system detects a vehicle ahead
C) When the vehicle speed drops below 15 kph
D) When a sufficiently illuminated built-up area is detected

2. How is the Headlight Assist System activated?

A) Either via the MMI panel or via the menu in the dash panel insert (depending on vehicle)
B) Using the Headlight Assist button E699 in the dash panel insert
C) By flicking the main-beam stalk forward
D) By turning the rotary light switch to the "Headlight Assist" position

Annex

3. How does the Headlight Assist System monitor the vehicle's surroundings?

A) Using a separate camera integrated in the base of the rear-view mirror
B) It uses the radar sensor of the ACC system
C) It uses the camera of the Audi lane assist system
D) By means of an infrared sensor located behind the vehicle's radiator grille

Solutions: 1) B,D 2) C 3) A

23

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Technical specifications
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Technical status: 04/08

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