AUDI A6 ALLROAD 1999 C5 / 2.G Pneumatic Suspension System

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1 237 8496513
BL NSL 31 58l RF BR 30 34 58r 3110 11 12
The trailer operation signal …
..... comes from the F216 contact switch in the
trailer socket.
When the plug is connected, contact switch
F216 connects control unit J197 to earth.
See also “Trailer operation”.
Headlamp range control signal
As changing vehicle levels is axle-based (i.e.
for both sides of an axle at once), this would
produce a short-term visibility range
reduction when driving at night.
For this reason, the allroad quattro is fitted
with an automatic dynamic headlamp control
system (also without gas-discharge
headlamps). The automatic dynamic
headlamp range control system maintains the
light beam at a constant angle while the
vehicle level changes.
In order to prevent irregularities in the road
surface, such as bumps or potholes, from
causing the headlamp range to alter
unnecessarily, long reaction times are set
when the vehicle is travelling at relatively
constant speeds (little or no acceleration). If level change takes place (e.g. motorway
mode), the 4-level air suspension control unit
J197 transmits a voltage signal to the
headlamp range control unit J431.
This activates the HRC immediately and
controls the bodywork movements.
Level change process:
Raising - rear axle first, then front axle
Lowering - front axle first, then rear axle
243_014
Trailer socket to the self-levelling suspension
control unit J197 (pin 2/10)
from the rear fog light
switch
F216

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Interfaces
pt° M
1
A
B
C
D
234
IVIIIIII
567
912
8
MM
31
Functional diagram
Terminal 15 Terminal 30
T. 3 4Terminal 30
S S S
N150
N151
N311 N148
N149
G291
V66
G290N111
J197
G76 G77 G78 G289
J431
V48 V49 E281243_038 J403
F216

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Key to function diagram
E281 Self-levelling suspension operating
unit
F216 Contact switch for switchable rear fog
light
G76 Self levelling suspension sender, RL
G77 Self levelling suspension sender, RR
G78 Self levelling sender, FL
G289 Self levelling suspension sender, FR
G290 Compressor temperature, self-
levelling suspension sender
G291 Self-levelling suspension pressure
sender
J197 Self-levelling suspension control unit
J403 Relay for self-levelling suspension
compressor
J429 Control unit for central locking
J431 Control unit for headlamp range
control
N111 Discharge valve for self-levelling
suspension
N148 Valve for FL suspension strut
N149 Valve for FR suspension strut
N150 Valve for RL suspension strut
N151 Valve for RR suspension strut
N311 Valve for self-levelling suspension
pressure accumulator
K134 Self-levelling suspension warning
lamp
V48 Left headlamp range control motor
V49 Right headlamp range control motor
V66 Self-levelling suspension compressor
motor= Input signal
= Output signal
= Positive
= Earth
= Bi-directional
= CAN bus/signal wire
Auxiliary signals:
CAN low
CAN high
Door contact signal
Diagnostic connector for K wire
Vehicle locked signal
Trailer operation signal (F126)
Terminal 50 signal
Driving speed signal
Terminal 56
Diagnostic connector for K wire
to the instrument cluster
Driving speed signal from ABS control unit,
speed sensor output, rear left
1
2
3
4
5
6
7
8
I
II
III
IV
Terminal 58s
Terminal 58d
ESP button
ESP button
A
B
C
DHeadlamp range control signal
9
Power supply J431
10

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However, all level sensors (left and right) are
required in the air suspension system run-up
and run-on mode (ignition OFF).
To allow the left-hand level sensors to deliver
measured values in the case of the 4-level air
suspension in the allroad quattro, power is
supplied to control unit J431 (HRC) from
control unit J197).
This ensures that voltage is supplied to all
level sensors when control unit J197 is active.
Self-levelling suspension
control unit J197
The central element of the system is the
control unit which, in addition to its control
functions, enables the monitoring and
diagnosis of the entire system.
The control unit detects the signal from the
level sensors and uses it to determine the
current vehicle level. This is compared with
the reference level and corrected if necessary,
depending upon further input variables
(interfaces) and its internal control
parameters (reaction times and level
deviations).
It differentiates between various control
situations and controls them via the relevant
control concepts (see Control concept).
Comprehensive self-diagnosis facilitates
inspection and service of the system (see
Workshop Manual).
There are two control units currently in use,
depending on the country.
Control units with the part numbers
4Z7 907 553A and 4Z7 907 553B have different
control strategies (see page 10 onwards).
A common control strategy for all countries
(as for Index “B”) is planned for the future.
Control concepts
243_039
The system can be tested via the self-
diagnosis or test adapter 1598/35.
For further information, see “Service”
chapter.
Address word 34
Power supply to the headlamp range control
system
As previously described in the “Level sensors”
section, voltage is supplied to the left-hand
level sensors by the headlamp range control
unit J431)
Headlamp range control requires neither run-
up nor run-on times, so the voltage is
normally supplied to control unit J431 via
terminal 15 (ignition ON) (see function
diagram, page 32).

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Level change process:
Raising - rear axle first, then front axle
Lowering - front axle first, then rear axle
Modes
Height mode/driving mode
Reaction times upon level deviation
Control characteristics during level change
Level change is basically performed axle by
axle, whereby level differences between the
left and right sides are compensated (e.g. if
loaded on one side).Driving speed Reaction time
<5 km/h
Height modeapprox. 5 seconds
approx. 1 second at
extremely low level
>10 km/h
Driving modeapprox. 50 seconds or
15 minutes
depending on the level
deviation
Run-on mode/run-up mode
The run-on mode enables the compensation
of level deviations after the vehicle has been
parked (e.g. caused by passengers leaving the
vehicle or unloading the vehicle) and before
driving off (e.g. caused by intense cooling,
leakage or loading).
In this mode, delay times before commencing
a journey are kept to a minimum.After “Ignition OFF”, the control unit is in the
so-called run-on mode. The control unit
remains active for a maximum of 15 minutes
(via terminal 30) until it goes into sleep mode.
Due to the limited energy available when the
engine is switched off, control limits are
extended and controls are limited in both
number and duration.

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Control concepts
The system can switch between sleep mode
and run-on/run-up mode, triggered via the
door contact signal, a maximum of 15 times.
For the 15 subsequent wake-up procedures,
the system switches to sleep mode after only
1 minute.
The system can then only be activated via
terminal 15 and/or the speed signal. Sleep mode
To minimise electricity consumption the
control unit switches to “system idle” (sleep
mode) after 15 minutes.
There is no level adjustment in sleep mode.
“Wake-up” is primarily triggered by the door
contact signal. If the door contact signal fails,
the system is activated when the ignition is
switched “ON” or by the driving speed signal.
The vehicle should be raised as quickly
as possible in order for the control unit
to recognise the lifting-platform mode.
It is often advisable to switch off the
system during repair work (e.g. during
axle measurement or if the pressure
lines have been detached, in order to
prevent the compressor running
unnecessarily).
242_010
Lifting platform mode
The control unit evaluates the level signals
while a stationary vehicle is being lowered
and thereby initiates lifting platform
operating mode.
The aim of the lifting platform mode is to
prevent excessive discharge of the air springs
when the vehicle is completely raised.

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In trailer operation, normal mode must
always be selected and care must be
taken that the system is switched to
manual mode (e.g. no automatic
switching to manual mode if trailer
operation signal fails).
In difficult driving conditions, high
level 1 or high level 2 can be selected,
however, normal level must be selected
before a driving speed of 35 km/h is
exceeded.
Driving at low level or in automatic
mode is not permitted.
Trailer operation
The correct position of the tow bar on the
trailer attachment during trailer operation is
indicated in normal mode.
Contact switch F216 in the 13 pin trailer
socket is used to signal that the trailer plug is
inserted, i.e. indicates trailer operation (see
description “Trailer operation signal”.
If trailer operation is recognised, the manual
mode is automatically activated (LED “man”
lights up) whereby the automatic raising
process is stopped.
Normal level is set by the driver via control
unit E281.
243_015
Normal level

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Special tools
Adapter cable 1598/35 with test box 1598/14
are used for fault finding and function testing
of sensors and signals of the 4-level air
suspension system.
As the pin assignment of the test box is not
compatible with the pin assignment of
control unit J197, pin template
V.A.G 1598/35-1 must be used.
Pin assignment is only possible by means of
pin template V.A.G 1598/35-1.
Service
Due to the limited number of
connections to test box V.A.G. 1598/14,
not all interfaces in control unit J197
are wired.
243_016
243_017
Adapter cable 1V.A.G 598/35
Pin template V.A.G. 1598/35-1
Test box
V.A.G. 1598/14

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Basic system setting
The basic system setting of the reference
level in the 4-level air suspension system is
performed by inputting body-level measured
values at normal level.
The measured value, the vertical dimension
from the wheel centre to the wheel cut-out,
must be input into the control unit using a
diagnostic tester in function 10 “Adaption”.
(Procedure, see Workshop Manual).
The codes serve to define the reference value
for normal level (allroad quattro 402 mm).
This means that design-specific values of the
level sensors are adjusted for this dimension.
Due to the tolerances of the components
involved, there is a certain deviation between
actual (measured) and reference (defined)
values.
By the inputting of the actual value, control
unit J197 recognises a potential difference to
the reference value. based on which the
design-specific values from the level sensors
are adapted.
Advantages of the measurement method:
•No influence of the correct basic setting
due to …
... different tread depths and tyre pres-
sures.
... minor unevenness of the road surface.
... different tyre sizes.
•Simple to perform.Codes for the allroad quattro
25500
Position Meaning
X00001 = Headlamp control not
installed
2 = Headlamp control installed
0X0005 = Reference height, front
axle 402 mm
00X005 = Reference height, rear axle
402 mm
000X00 = Vacant
0000X0 = Vacant
243_018
402 mm402 mm

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Self-diagnosis
Address word: 34 Self levelling suspension
Both generations of diagnostic tester
(V.A.G. 1551/1552 and VAS 5051) are suitable
for communication with the 4-level air
suspension control unit.
Due to the limited capacity of the tester
program cards, there are display text
limitations in the case of diagnostic testers
V.A.G. 1551 and 1552 (see. e.g. Workshop
Manual, Self-diagnosis function 03, Final
control diagnosis).
Service
198_039