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

10
If the vehicle is at high level 2, it will lower
automatically to high level 1 at a speed of
> 35 km/h. The system will respond to a
request to shift to high level 2 only up to a
speed of < 30 km/h.
At a speed of > 80 km/h in high level 1, the
system will automatically lower the vehicle to
normal level.. The system will respond to a
(manual) request to shift to high level 1 only
up to a speed of < 75 km/h.
During driving operation, no automatic
raising to high level 1 or 2 is performed. It
must be selected manually by the driver.
The parking level is an exception. In this
mode the vehicle automatically rises to high
level 1 once it has been parked and locked
(see parking level control). There are two control units currently in use,
depending on the country.
The control strategies described below relate
to the control unit 4Z7 907
553A.
The differences in control units with part
numbers 4Z7 907
553B
are described
subsequently.
See also page 34, “Self-levelling control unit
J197”.
Control strategies
4Z7 907 553A
Automatic lowering
As mentioned previously, the driver can select
the appropriate level by actuating the “raise”
or “lower” buttons.
The following preconditions relating to
driving speed apply for high level 1 and high
level 2.
Control strategies
0 35 80 120
0
5 35 70 120

Automatic lowering
Lowering processes
after 30 seconds
after 30 seconds
Raising processes
after 120 seconds
Raising to parking level
Immediate raising Speed km/h
Speed km/h
243_026
LL NL HL1HL2
LL NL HL1HL2

11
Motorway mode
If the vehicle travels for longer than
30 seconds at over 120 km/h (vehicle is
already at normal level), it will automatically
be lowered to low level.
This reduces air resistance (saves fuel) and
lowers the vehicle’s centre of gravity
(improved driving dynamics).
PL (=HL1) is only cancelled when a
driving speed of 80 km/h is exceeded
(see automatic lowering) or when
switching to a lower level manually.
If the vehicle is already in HL2 it is not
lowered to parking level.
Manual mode
The motorway mode and parking level
control functions are deactivated in
manual mode (see Automatic
switching page 9).
The vehicle rises automatically to normal level
at the following speeds and time thresholds:
Vehicle speed Time
<70 km/h >120 seconds
<35 km/h >30 seconds
<5 km/h immediately

Parking level control
The parking level ensures that the vehicle is
maintained at a suitable level after parking for
a long period of time (normal volumetric
reduction due to cooling or diffusion).
It also facilitates entering and loading the
vehicle and optimises the appearance of the
stationary vehicle.
The parking level corresponds to high level 1
(HL1).
The vehicle is set to parking level
–when the system is in run-on mode and the
vehicle is locked from the outside.
–when sufficient pressure is present in pres-
sure accumulator.
–when the system is not switched to manual
mode.

15
Rear suspension strut
The bayonet connection must be absolutely
clean and is greased with a special lubricant
before installation (see Workshop Manual).
For installation, the air spring is pushed on
and then turned.
Operating pressure of the air springs
front rear
Minimum
operating
pressure6.0 bar 6.1 bar
Nominal
operating
pressure6.4 bar 8.5 bar
Maximum
operating
pressure9.0 bar 10.9 bar
Always check for leaks on the O-ring
seals at the raised areas. The sealing
surfaces must be clean, free from
corrosion and pitting (aluminium parts)
and greased as required (see Workshop
Manual).
Design and function of the rear air
springs, see SSP 242, from page 40
onwards.
Full description of the PDC damper, see
SSP 242, from page 33 onwards.

243_005
O-ring
Locking cap

21
The 4 air spring valves N148, N149, N150,
N151 and accumulator valve N311 are
combined in one valve unit. They are
designed as 2/2 way valves and are closed
without current. The pressure on the air
spring side/accumulator side acts in the
closing direction.
The pressure lines are colour coded to
prevent confusion when connecting.
The colour allocation on the valve block is
echoed by corresponding coloured dots on
the connectors.
Solenoid valves
The 4-level air suspension has 6 electric
solenoid valves.
Discharge valve N111 forms a functional unit
together with the pneumatic discharge valve
and is integrated into the dryer housing (see
page 17).
Discharge valve N111 is a 3/2 way valve and is
closed without current.
The pneumatic discharge valve acts as a
pressure limiter and residual pressure
retaining device.
243_010Valve unit with
N148, N149, N150, N151
and N311
Compressor
pressure connectorFront leftPressure accumulator
Rear right
Rear left Front right

30
The driving speed signal …
... is a square-wave signal produced by the
dash panel, the frequency of which is
changed in accordance with the vehicle
speed.
... is required in the evaluation of the driving
condition (stationary/driving mode) and
thereby for selection of the control criteria
(see “Control concept”).
The interface for the driving speed signal is
redundant, as the information regarding
speed is also transmitted by the CAN bus.
K wire
Communication for self-diagnosis between
control unit J197 and the diagnostic tester
takes place via the familiar K wire by means of
conventional data messages.
The self-diagnosis K wire must not be
confused with the K wire connecting
operating unit E281 to control unit J197.
Power supply to the headlamp range control
system
In the case of 4-level air suspension in the
allroad quattro, the headlamp range control
system voltage is supplied by the air
suspension control unit J197. Further
information can be found under Control unit
J197 on page 34.
Additional interfaces
The door contact signal …
... is an earth signal from the control unit for
central locking. It indicates that the door or
boot lid/tailgate is open.
... serves as a “wake-up pulse” for transfer
from sleep mode to run-on mode (see
“Control concepts”).
Terminal 50 signal...
... signals actuation of the starter and is used
to switch off the compressor during start-up.
If a low position is detected following a wake-
up pulse, the compressor is activated
immediately in order to allow the vehicle to
drive off as quickly as possible.
The compressor is switched off during start-
up in order to save battery power and ensure
starting power.
The vehicle locking signal …
... is used as information for parking level
control
... is an earth pulse coming from the control
unit for central locking J429
... is not detected by the self-diagnosis.
Parking level control is not performed if this
signal fails.
Interfaces
The vehicle locking signal is not
required for vehicles without parking
level control (see pages from 10
onwards and 34 onwards).

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
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