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

27
Warning lamp K134...
... illuminates for one second when
terminal 15 is ON (self-test).
... is constantly illuminated in the
case of relevant system errors or
when the system is switched off.
... is constantly illuminated during
basic system setting and when
basic system setting has not been
performed successfully.
... flashes in the case of extremely
low or high levels.
... flashes during final control
diagnosis.
242_050 Warning lamp K134
As no magnetic materials are required,
temperature and age cause only minimal
variances in the measured values. Such
variances are caused by a reduction in the
strength of the magnetic field of permanent
magnets over time or due to temperature
changes. Level sensors, summary
The advantages of the angle sensor are the
proportional measurement process along
with their contact-free and therefore wear-
free operation.
The generation of ratios (proportional
measurement) means that the output signal
proportional to the angle is largely
independent of mechanical tolerances such
as distance changes, axle movement or
inclination errors. Magnetic interference is
also largely suppressed due to the generation
of ratios.

33
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

34
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).

38
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

39
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