Land Rover Anti Lock Control Traction Control Rover Manual

							The air suspension control module will stop all height
change requests while any of the doors are open. Vehicle
levelling continues with a door open by keeping the
vehicle at the height when the door was opened if the
vehicle load changes.
Diagnostics
The air suspension control module can store fault codes
which can be retrieved using T4. The diagnostic
information is obtained via the diagnostic socket which
is located in the lower instrument panel closing panel,
on the drivers side, below the steering column.
The diagnostic socket allows the exchange of
information between the various control modules on the
bus systems and T4 or a diagnostic tool. This allows the
fast retrieval of diagnostic information and programming
of certain functions using T4.
Fault Detection
The air suspension control module performs fault
detection and plausibility checks. Fault detection is
limited to faults that the control module can directly
measure as follows:
•Sensor electrical hardware faults
•Valve electrical hardware faults
•Sensor and actuator supply faults
•Bus failures
•Control module hardware errors.
Plausibility checks are checks on signal behaviour, as
follows:
•Average height does not change correctly
•Height changes too slowly
•Gallery pressure
•Does not increase fast enough when reservoir
filling requested
•Increases when system is inactive
•Too low when lifting is requested
•Increases too rapidly when filling reservoir
•Does not decrease when gallery is vented
•Pressure varies too much when inactive.
•Compressor temperature
•Sensor voltage too large - head and brush sensors
(short circuit to battery)
•Takes too long to be readable after suitable
compressor run time - head and brush sensors
•Does not increase when compressor active - head
sensor only
•Sensor activity
•Signal floating
•Constant articulation when moving
When a fault is detected, the air suspension control
module will attempt to maintain a comfortable ride
quality and where possible will retain as much
functionality as possible.
The system functionality depends on the severity of the
fault.
Faults
Faults are categorised into order of severity and effect
on the system as follows (with 1. being a minor fault
and 5. being a major fault):
–Height sensor faults (hardware faults) and reservoir
valve block failure
•Retain full functionality with no refinements,
e.g. cross-link valves inoperative, no
compensation for uneven surfaces.
–Pressure sensor faults, compressor faults, corner
valves stuck shut
•Road speed signal not available
•Vehicle returns to on-road mode height when next
requested
•Levels at current height.
–Reservoir valve stuck open, exhaust valve stuck shut
if below on-road mode height, corner valves stuck
open if above on-road mode height
Vehicle Dynamic SuspensionLesson 2 – Chassis
63Technical Training (G421053) 
						

							Vehicle returns to on-road mode height when next
requested
•
•Does not level at current height.
–Failure of multiple height sensors, cross-articulation
when driving, calibration corrupted
•Vehicle lowers to bump stops.
–ABS module failure, CAN bus failure
•If the air suspension control module loses
communications with the ABS module or the
ABS module reports a fault, the air suspension
control module immediately returns to the
default height, which is below the on-road ride
height. Once at the default height, the control
module will continue to level the vehicle at this
height. It is unlikely that the fault will be in the
air suspension control module. When the fault is
repaired, the air suspension control module will
resume full functionality but the error will remain
in the control module memory.
For major faults the control module will not level the
vehicle at the current ride height. The control module
freezes height changes until it receives a manual or
automatic request for height change. The control module
will return to standard height if possible and freezes
once standard height is achieved.
If the suspension is above the on-road height and the
air suspension control module cannot lower the
suspension, all height changes will be frozen. The
control module will issue a message on the high speed
CAN bus which is received by the instrument cluster
which displays a maximum advisable speed in the
message center. an immediate freeze of the vehicle
height is caused by the following:
•Failure of more than one height sensor - vehicle on
bump stops
•Implausible articulation symptoms detected - vehicle
on bump stops
•Valve or solenoid failure - corner valve stuck open
below on-road mode height or exhaust valve stuck
shut above on-road mode height
•Stuck corner or whole vehicle (diagnosed using
plausibility of the sensor inputs).
If height change is not possible, e.g. exhaust valve failed
closed at off-road height or compressor failed at access
height, the control module will not level or change
height.
If the air suspension control module has a hardware
fault, the control module will disable all air suspension
functions. Detectable hardware errors include memory
error, control module failure, calibrations errors.
Fault Messages
The air suspension has two methods which it can use
to inform the driver of a fault in the air suspension
system; the air suspension switch LEDs and the
instrument cluster message center.
When minor faults occur and the air suspension control
module is able to level the vehicle to the current ride
height, the air suspension switch LEDs will display the
current ride height.
If the air suspension control module suffers a major
failure and there is no air suspension control, all the
control switch LEDs will remain off.
If a fault occurs and the air suspension control module
can determine the ride height and the vehicle is not
above on-road mode height, the driver will be notified
via a air suspension fault max speed 18.6 mph (30
km/h) message in the message center.
If the control module cannot determine the height of the
vehicle, or the vehicle is above on-road mode height,
cannot be lowered and the vehicle speed is too high, an
air suspension fault message is displayed.
If the vehicle is restricted to on-road mode height an air
suspension fault normal height only message is
displayed.
(G421053) Technical Training64
Lesson 2 – ChassisVehicle Dynamic Suspension 
						

							AIR SUSPENSION SWITCH
Crawl mode lamp1
Access mode lamp2
Lowering lamp3
On-road mode lamp4
Air suspension switch5
Raising lamp6
Off-road mode lamp7
Terrain Response™ rotary control8
Transfer box range switch9
Hill Descent Control (HDC) switch10
The air suspension control switch is located in the center
console, behind the manual or automatic transmission
selector lever. The switch is a three position,
non-latching switch which allows selection of the
following driver selectable modes:
•Off-road mode
•On-road mode
•Access mode
•Crawl (locked at access) mode.
The air suspension switch can be moved forwards or
backwards from its central position. The switch is
non-latching and returns to the central position when
released. The switch completes an earth path to the air
suspension control module when operated. This earth
path is completed on separate wires for the raise and
lower switch positions, allowing the control module to
determine which selection the driver has made.
The switch has six symbols which illuminate to show
the current selected height and the direction of
movement. The raise and lower symbols will flash and
a warning tone will be emitted from the instrument
cluster sounder when a requested height change is not
allowed, i.e. vehicle speed too fast.
A flashing symbol indicates that the air suspension
system is in a waiting state or that the system will
override the drivers selection because the speed
threshold is too high.
The driver can also ignore the systems warnings signals
and allow the height to change automatically. For
example, increasing the vehicle speed to more than 25
mph (40 km/h) will cause the control module to
automatically change the ride height from off-road mode
to on-road mode.
Vehicle Dynamic SuspensionLesson 2 – Chassis
65Technical Training (G421053) 
						

							FRONT AND REAR AXLE VALVE BLOCKS
Isolation rubber mounts (3 off)1
Location slots2
Front valve block, valves and solenoid assembly3
Front bumper armature4
Electrical connector5
LH air spring damper module air harness
connection
6
Air inlet/outlet connection7
RH air spring damper module air harness
connection
8
Rear valve block, valves and solenoid assembly9
RH air spring damper module air harness
connection
10
Air inlet/outlet connection11
LH air spring damper module air harness
connection
12
Rear suspension turret13
The front and rear axle valve blocks are similar in their
design and construction and control the air supply and
distribution to the front or rear pairs of air spring damper
modules respectively. The difference between the two
valves is the connections from the valve block to the
left and right hand air spring damper modules and the
valve size. It is important that the correct valve block
is fitted to the correct axle. Fitting the incorrect valve
block will not stop the air suspension system from
functioning but will result in slow raise and lower times
and uneven raising and lowering between the front and
rear axles.
The front valve block is attached to the right hand end
of the front bumper armature assembly. The valve block
has three attachment lugs which are fitted with isolation
rubber mounts. The rubber mounts locate in slots in the
armature. The valve lugs locate in the holes above the
slots and are pulled downwards into positive location
in the slots.
The rear valve block is located on the forward face of
the left hand rear suspension turret. The valve block has
three attachment lugs which are fitted with isolation
rubber mounts which locate in a bracket with three
slotted holes. The bracket is attached to the left hand
(G421053) Technical Training66
Lesson 2 – ChassisVehicle Dynamic Suspension 
						

							side of the chassis. The isolation rubber mounts locate
in the V shaped slots and are pulled downwards into
positive location in the slots.
The front and rear valve blocks each have three air pipe
connections which use Voss type air fittings. One
connection is an air pressure inlet/outlet from the
reservoir valve block. The remaining two connections
provide the pressure connections to the left and right
hand air springs.
Each valve block contains three solenoid operated
valves; two corner valves and one cross-link valve. Each
of the valve solenoids is individually controlled by the
air suspension control module. The solenoids have a
resistance value of 2 Ohms at a temperature of 20°C
(68°F).
Corner Valves
The corner valves control the flow of air into and out
of the individual air springs. When the solenoid is
de-energised, the corner valves are held in a closed
position by internal springs. When the solenoid is
energised, the valve armature moves and allows air to
flow into or out of the air spring.
Cross Link Valves
The cross-link valve provides a connection between the
two air springs on the same axle. When de-energised,
the cross-link valve prevents air passing from one air
spring to another. When the solenoid is energised, the
valve spool moves and allows air to pass from one air
spring to the other. This increases wheel articulation
and improves ride comfort at low vehicle speeds.
RESERVOIR VALVE BLOCK
Chassis mounting bracket1
Location slot2
Isolation rubber mounts (3 off)3
Electrical connector4
Reservoir valve block, valves and solenoid
assembly
5
Reservoir connection6
Rear valve block connection7
Vehicle Dynamic SuspensionLesson 2 – Chassis
67Technical Training (G421053) 
						

							Front valve block connection8
Air supply unit connection9
Pressure sensor10
The reservoir valve block controls the storage and
distribution of air from the reservoir. The reservoir valve
block also contains the system pressure sensor.
The reservoir valve block is attached to a bracket on the
outside of the left hand chassis rail, between the
reservoir and the air supply unit. The valve block is
located within the air supply unit acoustic box to protect
it from dirt ingress and damage from stones. The valve
block has three attachment lugs which are fitted with
isolation rubber mounts which locate in the chassis
bracket which has three slotted holes. The isolation
rubber mounts locate in the V shaped slots and are
pulled downwards into positive location in the slots.
The valve block has four air pipe connections which
use Voss type air fittings. The connections provide for
air supply from the air supply unit, air supply to and
from the reservoir and air supply to and from the front
and rear valve blocks. The connections from the air
supply unit and the front and rear control valves are all
connected via a common gallery within the valve and
therefore are all subject to the same air pressures.
The valve block contains a solenoid operated valve
which is controlled by the air suspension control
module. The solenoid valve controls the pressure supply
to and from the reservoir. The solenoid has a resistance
value of 2 Ohms at a temperature of 20°C (68°F). When
energised, the valve spool moves allowing air to pass
to or from the reservoir.
The valve block also contains a pressure sensor which
can be used to measure the system air pressure in the
air springs and the reservoir. The pressure sensor is
connected via a harness connector to the air suspension
control module. The control module provides a 5V
reference voltage to the pressure sensor and monitors
the return signal voltage from the sensor.
Using this sensor, the control module controls the air
supply unit operation and therefore limits the nominal
system operating pressure to 244 lbf/in2 (16.8 bar gage).
(G421053) Technical Training68
Lesson 2 – ChassisVehicle Dynamic Suspension 
						

							AIR SUPPLY UNIT
Mounting bracket1Air dryer2
Vehicle Dynamic SuspensionLesson 2 – Chassis
69Technical Training (G421053) 
						

							Pilot exhaust valve solenoid and temperature
sensors harness connector
3
Motor harness connector4
Intake port5
Pilot exhaust valve6
Exhaust valve7
Isolation mounting rubber (2 off)8
Electric motor9
Isolation mounting rubber (1 off)10
Pilot air pipe11
Pressure outlet to pilot exhaust valve12
Compressor cylinder head temperature sensor13
Compressor14
The air supply unit is located on the outside of the left
hand chassis rail, forward of the upper control arm. The
unit is attached to the chassis rail with three bolts and
is protected by an acoustic box.
Acoustic Box
Upper cover1
Lower cover2
Air supply unit3
Reservoir valve block4
The acoustic box, which comprises of two parts; upper
and lower, surrounds the air supply unit. The acoustic
box is a plastic moulding which is lined with an
insulating foam which controls the operating noise of
the air supply unit. The reservoir valve block is also
located in the acoustic box, forward of the air supply
unit.
(G421053) Technical Training70
Lesson 2 – ChassisVehicle Dynamic Suspension 
						

							The air supply unit comprises the following major
components:
•A piston compressor
•A 12V electric motor
•A solenoid operated pilot valve
•An exhaust valve
•An air dryer unit
The air supply unit can be serviced in the event of
component failure, but is limited to the following
components; air dryer, pilot exhaust pipe and the rubber
mounts.
The air supply unit is attached to a bracket which is
bolted to the chassis. The unit is mounted to the bracket
with flexible isolation mounting rubbers which assist
with preventing operating noise being transmitted to the
chassis.
Removal of the air supply unit does not require the
whole air suspension system to be depressurised. The
front and rear valve blocks and the reservoir valve block
are normally closed when de-energised, preventing air
pressure in the air springs and the reservoir escaping
when the unit is disconnected.
There are a number of conditions that will inhibit
operation of the air supply unit. It is vitally important
that these system inhibits are not confused with a system
malfunction. A full list of air supply unit inhibits are
given in the air suspension control module section in
this chapter.
Air Supply Unit - Sectional View
Exhaust valve cap1Plunger2
Vehicle Dynamic SuspensionLesson 2 – Chassis
71Technical Training (G421053) 
						

							Valve seat3
Intake silencer port4
Delivery valve5
Valve guide6
Cylinder head7
Dryer case8
Desiccant9
Pilot exhaust line10
Isolation rubber mount11
Motor assembly12
Crankcase13
Crank14
Crankcase cover15
Connecting rod16
Piston17
Pilot exhaust valve18
Spring - pressure relief19
Pilot Exhaust Valve
A solenoid operated pilot exhaust valve is connected to
the air delivery gallery, downstream of the air dryer.
The pilot valve, when opened, operates the main
compressor exhaust valve. This allows the air springs
to be deflated when required.
When the solenoid is energised, pilot air moves the
exhaust valve plunger, allowing pressurised air from
the air springs and/or reservoir to pass via the reservoir
control valve to the air supply unit.
The solenoid has a resistance value of 4 Ohms at a
temperature of 20°C (68°F).
Exhaust Valve
The exhaust valve has three functions. It operates in
conjunction with the pilot exhaust valve to allow air to
be exhausted from the air springs and/or the reservoir
as described previously.
The valve also protects the system from over-pressure.
The valve is connected into the main pressure gallery
which is always subject to the system pressure available
in either the air springs or the reservoir. The valve is
controlled by a spring which restricts the maximum
operating pressure to between 333.5 to 370 lbf/in2 (23.0
to 25.5 bar).
The minimum pressure in the system is also controlled
by the exhaust valve to ensure that, even when deflated,
the air springs contain a positive pressure with respect
to atmosphere. This protects the air spring by ensuring
it can still roll over the piston without creasing.
Electric Motor
The electric motor is a 12V dc motor with a nominal
operating voltage of 13.5V. The motor drives a crank
which has an eccentric pin to which the compressor
connecting rod is attached.
The motor is fitted with a temperature sensor on the
brush PCB assembly. The sensor is connected to the air
suspension control module which monitors the
temperature and can suspend motor operation if an
overheat condition occurs.
Compressor
The compressor comprises a motor driven connecting
rod and piston which operate in a cylinder with a
cylinder head. The motor rotates the crank moving the
piston up and down in the cylinder bore. The air in the
cylinder is compressed with the up stroke and is passed
via delivery valve, through the air dryer into the system.
(G421053) Technical Training72
Lesson 2 – ChassisVehicle Dynamic Suspension