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