2002 LAND ROVER DISCOVERY earth

FRONT SUSPENSION
60-22 DESCRIPTION AND OPERATION
Failure modes
Failures where the vehicle can still be driven safely are indicated by the ACE warning lamp illuminating continuously
with an amber colour. The amber warning lamp will remain illuminated until the ignition is turned off. For all faults the
warning lamp will only illuminate again if the fault is still present. Failures which require the driver to stop the vehicle
immediately are indicated by the ACE warning lamp flashing with a red colour and an audible warning. All faults are
recorded by the ACE ECU and can be retrieved with diagnostic equipment.
The following tables show the type of system failures and their effects on the system operation. Torsion bar 'floppy'
means that fluid is allowed to circulate freely through the system. With no pressure in the actuators the torsion bar will
have no effect on vehicle roll. 'Locked bars' means that all pump flow is directed through the valve block and returns
to the reservoir. Both DCV's close and fluid is trapped in the actuators but can flow from one actuator to the other via
the valve block. In this condition the torsion bar will perform similar to a conventional anti-roll bar, resisting roll but still
allowing the axles to articulate.
Acceleration sensors
Pressure transducer
14 Reverse switch Input
15 Accelerometer - lower (signal) Input
16 Pressure transducer (signal) Input
17 Accelerometer - upper (signal) Input
18 Accelerometer - upper (supply) Output
19 Engine speed Input
20 Main earth 1 -
21 Pressure transducer (earth) Input
22 DCV 2 (earth) Input
23 DCV 1 (earth) Input
24 DCV 1 & 2 (supply) Output
25 Pressure control valve (earth) Input
26 Not used -
27 Pressure control valve (supply) Output
28 Main supply (+ V Batt) Input
29 to 31 Not used -
32 Main earth 2 -
33 Accelerometer - lower (signal) Input
34 Accelerometer - upper (signal) Input
35 Not used -
36 Warning lamp Output
Failure Effect
Valve stuck closed No ACE control
Short circuit - Ground No ACE control
Short circuit - VBatt No ACE control
Loose sensor Erractic ACE activity when driving in straight line
Failure Effect
Short circuit - VBatt Large sensor dead band - possible random movementsPin No. Description Input/Output

REAR SUSPENSION
DESCRIPTION AND OPERATION 64-15
Height sensors
1Spacer
2Link end
3Link
4Link end
5Arm
6Sensor body
Two height sensors are located on the outside of each chassis longitudinal forward of the rear axle. Each sensor body
is attached to a fabricated bracket and secured with two screws. The sensor is attached to the top of each radius arm
by an arm, a link and two link ends. The link ends allow articulation of the arm to allow for suspension travel. The lower
link arm is attached to a lug of the top of the radius arm and is secured with a bolt and locknut.
The sensor body and arm are manufactured from moulded nylon. The two link ends are made from natural rubber
and the link is made from mild steel. The rubber link ends allow flexibility of the arm and resistance to damage.
Each sensor is connected to the main chassis harness by a multiplug. The three pin multiplug provides an earth, a 5
V supply voltage and an output signal voltage to the SLABS ECU.
Each sensor operates on the Hall effect principle. A magnet is attached to the shaft and rotates with movement of the
arm. The magnetic flux generated acts on a Hall effect sensor and depending on its position varies the current across
the sensor. This current is measured and amplified and passed to the SLABS ECU as a linear output voltage signal,
which varies depending on the angular position of the sensor. The signal information is processed and the ECU can
determine the vehicle height.
When the sensors are replaced or removed for any reason, a calibration procedure is required to recalibrate the
sensors and the SLABS ECU. The calibration procedure requires the use of TestBook and calibration blocks to set
the axle to chassis height to a known value.
If faults occur with the height sensors, fault codes are stored in the SLABS ECU. The current and past fault codes can
be retrieved with TestBook.

REAR SUSPENSION
DESCRIPTION AND OPERATION 64-17
SLABS ECU
1SLABS ECU
2Bracket
3BCU (Ref. only)
4ACE ECU (Ref. only)
5Attachment nuts
The SLABS ECU is mounted on a bracket behind the passenger glove box and is identified from the other ECU's by
its five connectors. The five connectors are located on the lower face of the ECU and mate with five connectors from
the main harness. The twelve, six and eighteen pin connectors are used to supply inputs and outputs to and from the
ECU. The remaining connectors are used for the ABS operation.

+ BRAKES, DESCRIPTION AND OPERATION, Description.
The SLABS ECU receives a continuous battery supply from fuse 11 in the engine compartment fusebox. An ignition
'ON' signal is supplied from the ignition switch via fuse 28 in the passenger compartment fusebox. The ECU has the
ability to control when it requires power and is not reliant on the ignition signal for it to power up.
The ECU incorporates a counter which times the operation of the SLS system and prevents the compressor
exceeding its duty cycle. The ECU can remain powered for up to 1.5 hours after ignition off is sensed to allow the
counter to continue running to avoid an ignition cycle resetting the counter.
Opening any of the doors will power up the ECU, irrespective of ignition switch position. The door open signal is
sensed by the door switch completing an earth path which is sensed by the ECU. The ECU cannot differentiate
between any of the doors. The door open signal powers the ECU for up to 30 minutes to allow the vehicle to re-level
when a load is removed or passengers leave the vehicle.

REAR SUSPENSION
64-18 DESCRIPTION AND OPERATION
The ECU supplies a 5 V current to each of the height sensors. Each height sensor uses the current to supply an
analogue input to the ECU. The ECU can calculate from the input received from each height sensor the height of the
vehicle and can then power the air supply unit as necessary to raise or lower one or both air springs to level the
vehicle.
When SLS compressor operation is required, the ECU provides a battery supply to energise the SLS relay located in
the engine compartment fusebox. When the relay contacts close, a 12 V supply passes through fusible link 9 in the
engine compartment fusebox, through the relay contacts and operates the air supply unit compressor. The ECU will
then supply power to operate one or both air control valve solenoids and/or the exhaust valve solenoid to inflate or
deflate the air springs as required. The compressor does not need to be powered to deflate the air springs.
The ECU also controls the operation of the SLS audible warning, the SLS warning lamp and the ORM warning lamp.
When the ignition is switched to position II, the ECU performs a three second bulb check and illuminates the SLS and
ORM warning lamps in the instrument pack to check for operation. When the system is operating or a fault is sensed
by the ECU, the ECU will operate the appropriate warning lamp and audible warning as required. The audible warning
is operated by the Body Control Unit (BCU) when it receives a signal from the SLABS ECU. The audible warning is
emitted from a speaker at the rear of the instrument pack.
Depressing the ORM switch for a minimum of 0.5 seconds, completes an earth which the ECU uses as a signal to
initiate the ORM if conditions allow. When the ECU starts ORM, the same earth that was completed by the ORM
switch is pulled to earth by the ECU to activate the ORM warning lamp. The ECU checks for a further operation of the
ORM switch by continuously and very quickly removing the earth for the ORM warning lamp. If the ORM switch is
operated for more than 0.5 seconds, the ECU will detect this and de-activate the ORM.
The SLS part of the SLABS ECU also uses the road speed data generated within the SLABS ECU by the ABS system.
Operation of ORM and extended mode are road speed sensitive and use the ABS signal to monitor the vehicle speed.
When the accessory remote handset is used for the SLS lower and raise functions, the handset transmits RF signals
which are received by the same RF receiver used for the alarm/remote door locking system. The RF receiver passes
this data as a 25 Hz PWM signal to the BCU. The BCU then transmits this data to the SLABS ECU as raise or lower
data. TestBook is required to program the BCU for remote handset operation.
SLABS ECU connector pin details
Connector/Pin No. Description Input/Output
C0504
1 Battery supply Input
2 Ignition supply Input
5 K line (diagnostics) Input/Output
12 EarthInput
C0654
1 Left height sensor supply Output
2 Left height sensor earth Input
3 Left height sensor signal Input
4 Right height sensor supply Output

REAR SUSPENSION
DESCRIPTION AND OPERATION 64-19
Failure modes
Failures are indicated by the SLS warning lamp in the bottom left corner of the instrument pack illuminating
continuously in an amber colour. The following tables show the type of system failures and their effects on the system
operation.
Height sensors
Door Switch Inputs
SLS off-road mode switch
Air supply unit air control valves
Air supply unit compressor
5 Right height sensor earth Input
6 Right height sensor signal Input
C0655
1 Driver's door switch Input
2 Passenger and tail door switches Input
3 Left air valve Output
4 Right air valve Output
5 Exhaust valve Output
6 Air compressor (SLS relay) Output
7 Audible warning Output
8 SLS warning lamp Output
11 ORM switch/ORM warning lamp Input/Output
12 Remote handset raise/lower signal Input
Connectors and pins not listed are either not used or used by the brakes system.

+ BRAKES, DESCRIPTION AND OPERATION, Description.
Failure Effect
Sensor output stuck at 5 V Vehicle will not level
Sensor output stuck at 0 V Vehicle will not level
Mechanical link between radius arm and sensor broken Vehicle will not level
Failure Effect
Harness leads for open doors are are broken or shorted to
V Batt.Air suspension levels when one or more doors are open
Harness leads to door(s) shorted to earth Air suspension will not level
Failure Effect
Fault in wiring harness Off-road mode cannot be selected
Failure of off-road mode switch Off-road mode is activated when switch has not been
selected
Failure Effect
Valves open or short circuit Vehicle does not level or levels unevenly
Failure Effect
Faulty relay, harness fault or compressor fault Vehicle does not level upwards

BRAKES
DESCRIPTION AND OPERATION 70-11
Master cylinder assembly
Section through master cylinder assembly
1Reservoir filler cap
2Switch float
3Brake fluid reservoir
4Primary feed hole
5Valve pin
6Primary centre valve
7Primary piston
8Primary spring9Pressure chamber
10Cylinder
11Valve pin
12Secondary centre valve
13Secondary spring
14Pressure chamber
15Secondary piston
16Secondary feed hole
The master cylinder assembly produces hydraulic pressure to operate the brakes when the brake pedal is pressed.
The assembly is attached to the front of the brake servo assembly, and comprises a cylinder containing two pistons
in tandem. The rear piston produces pressure for the primary circuit and the front piston produces pressure for the
secondary circuit. A brake fluid reservoir is installed on top of the cylinder. The reservoir is internally divided to provide
an independent supply of fluid to each brake circuit, and so prevent a single fluid leak from disabling both primary and
secondary brake circuits. Should a failure occur in one circuit, the remaining circuit will still operate effectively,
although brake pedal travel and vehicle braking distances will increase. If the fluid level in the reservoir is too low, a
float operated switch in the reservoir filler cap connects an earth to the instrument pack, which illuminates the brake
warning lamp.

BRAKES
DESCRIPTION AND OPERATION 70-17
SLABS ECU
The SLABS ECU is attached to a bracket behind the front passenger glovebox. Brake related inputs are processed
by the SLABS ECU, which then outputs control signals to the ABS modulator. Five electrical connectors interface the
SLABS ECU with the vehicle wiring.
SLABS ECU connector pin details
Connector/Pin No. Description Input/Output
C0504
1 Battery supply Input
2 Ignition supply Input
3 Road speed Output
4 Rough road (V8 models only) Output
5 K line (diagnostics) Input/Output
7 Reverse gear Input
8 Return pump monitor Input
9 Brake warning lamp Output
10 Engine data (throttle position, torque, engine type, gearbox type) Input
11 Transfer box range Input
12 Earth-
13 ETC warning lamp Output
14 HDC switch Input
15 Neutral selected (automatic gearbox only) Input
16 HDC fault warning lamp Output
17 HDC information warning lamp Output
18 ABS warning lamp Output
C0505
1 Front left wheel speed Input
2 Front left wheel speed Input
3 Rear right wheel speed Input
4 Front right wheel speed Input
5 Front right wheel speed Input
6 Rear right wheel speed Input
7 Rear left wheel speed Input
8 Rear left wheel speed Input
C0506
1 Front left outlet solenoid valve Output
2 Front left inlet solenoid valve Output
3Earth-
4 Front right outlet solenoid valve Output
5 Front right inlet solenoid valve Output

BRAKES
DESCRIPTION AND OPERATION 70-23
Typical disabled times
Diagnostics
While the ignition is on, the diagnostics function of the SLABS ECU monitors the system for faults. In addition, the
return pump is tested by pulsing it briefly immediately after the engine starts provided vehicle speed exceeded 4.4
mph (7 km/h) during the previous ignition cycle. If a fault exists in a warning lamp circuit, the lamp will not illuminate
during the lamp check at ignition on but, provided there are no other faults, the related function will otherwise be fully
operational. If a fault is detected during the power up, the SLABS ECU stores a related fault code in memory and
illuminates the appropriate fault warning lamps. If a fault is detected later in the drive cycle, the SLABS ECU also
sounds the audible warning three times.
Fault codes and diagnostic routines can be accessed by connecting Testbook to the vehicle's diagnostic connector
in the driver's footwell.
Warning lamp fault operation
After detecting a fault, the SLABS ECU selects an appropriate default strategy which, where possible, retains some
operational capability. A shuttle valve switch fault and throttle position signal fault are classified as permanent faults.
If a permanent fault is detected, the related warning lamp illumination and default strategies are automatically
employed in subsequent ignition cycles, even if the fault is intermittent, until the fault has been rectified and cleared
from memory. If a non permanent fault is detected, the related warning lamp illumination and default strategies will
only be employed in subsequent ignition cycles if the fault is still present.
After rectification of an ABS sensor fault, the ABS and ETC functions are disabled, and the ABS warning lamp remains
illuminated after the lamp check, until vehicle speed exceeds 9.4 mph (15 km/h) (to allow additional checks to be
performed).
Vehicle speed, mph (km/h) Time, minutes
1.3 (2) 40
12.5 (20) 33
15.6 (25) 17
25.0 (40) 9
31.3 (50) 6
Item Check Warning lamp
ABS Brake ETC HDC
fault
ABS sensors Resistance (to check status) On On On On
Brake lamps relay Open/Short circuit Off Off Off On
Engine data Sticking throttle, signal failure, data corruption Off Off On On
Inlet solenoid valves Open/Short circuit On On On On
Outlet solenoid valves Open/Short circuit On On On On
Reference earth Connection to earth On On On On
Return pump monitor Correct pump operation On On On On
Return pump relay Open/Short circuit On On On On
Shuttle valve switches Open/Short circuit On On On On
SLABS ECU Internal failure On On On On
Supply voltages Range (10 to 16 V) On On On On