ignition LAND ROVER DISCOVERY 2002 Owners Manual

FRONT SUSPENSION
DESCRIPTION AND OPERATION 60-23
Road speed signal
Engine speed signal
Reverse gear signal
Ignition ON signal
Pressure control valve failure
Failure Effect
Open circuit No ACE control - 'Locked bars' condition
Short circuit - Ground No ACE control - 'Locked bars' condition
Short circuit - VBatt No ACE control - 'Locked bars' condition
Failure Effect
Open circuit No ACE control - 'Locked bars' condition
Short circuit - Ground No ACE control - 'Locked bars' condition
Short circuit - VBatt No ACE control - 'Locked bars' condition
Failure Effect
Open circuit No reverse signal to ECU. ACE active in reverse, may give
abnormal handling when reversing
Short circuit - Ground No reverse signal to ECU. ACE active in reverse, may give
abnormal handling when reversing
Short circuit - VBatt Permanent reverse signal to ECU. Permanent 'Locked
bars' condition
Failure Effect
Open circuit ECU does not receive ignition ON signal. No ARC control,
'Locked bars' condition
Short circuit - Ground ECU does not receive ignition ON signal. No ARC control,
'Locked bars' condition
Short circuit - VBatt Permanent ignition ON signal to ECU. Possibility of flat
battery
Failure Effect
Open circuit No ACE control
Short circuit - Ground No ACE control
Short circuit - VBatt No ACE control
Valve stuck open No ACE control
Valve stuck closed Maximum system pressure - no proportional control.
Pressure relief valve operating at 185 bar (2683 lbf.in
2)

REAR SUSPENSION
DESCRIPTION AND OPERATION 64-11
1Battery supply (via SLABS relay)
2Ignition supply
3RH height sensor
4LH height sensor
5Off-road mode warning lamp
6Audible warning speaker
7Instrument pack
8SLS warning lamp
9Fusible link 9
10SLS relay
11Air supply unit12RH air valve
13LH air valve
14Exhaust valve
15Diagnostic socket
16Off-road mode switch
17SLS remote handset
18Body Control Unit (BCU)
19Door switches
20SLABS ECU
21Engine Control Module (ECM)

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
64-20 DESCRIPTION AND OPERATION
Operation
Circuit diagram
1SLABS ECU
2Exhaust valve
3Restrictor
4Pressure limiting valve
5Silencer
6Inlet air filter
7Compressor
8Air dryer9Non-return valve
10RH air control valve
11RH air spring
12RH height sensor
13LH height sensor
14LH air spring
15LH air control valve
The SLS system is active when the ignition switch is in position II, when one or more doors are open and for up to
thirty minutes after all doors have been closed. If the rear axle is articulated by more than 100 mm (3.93 in), the ECU
will not activate the SLS system.
The air supply unit compressor will only operate to raise the rear of the vehicle when the engine is running, with the
exception of the remote handset operation which does not require the engine running. Three modes of SLS operation
are available; Normal Ride Height, Off-Road Mode (ORM) and Extended Mode. A fourth mode, transportation mode,
is programmed by TestBook for transport or recovery of the vehicle on a trailer.

REAR SUSPENSION
DESCRIPTION AND OPERATION 64-21
Normal ride height
When the vehicle is stationary, a door is open and the ignition is off, the SLS system will allow the rear of the vehicle
to lower to within 20 mm of the normal ride height as load is removed from the vehicle. The SLS system will only
operate the compressor to raise the rear of the vehicle when the engine is running, unless requested using the remote
handset.
Off-road mode (ORM)
ORM is used to raise the rear of the vehicle from normal ride height to the ORM ride height of 100 mm between the
tip of the bump stop and the axle.
ORM is activated by depressing the ORM switch located on the fascia for not less than 0.5 seconds. With the engine
running, all doors closed and the vehicle speed below 18 mph (30 km/h), the audible warning will sound once and the
ORM warning lamp in the instrument pack will start to flash when the switch is released. The compressor will be
started and the air control valves will be energised by the ECU to inflate the air springs and raise the rear of the vehicle.
When the full ORM height is reached, the ECU will terminate compressor operation and close the air valves. The ORM
warning lamp will stop flashing and remain continuously illuminated to inform the driver that the SLS system is in ORM.
When ORM is no longer required, depressing the ORM switch for not less than 0.5 seconds with all doors closed will
lower the SLS to normal ride height. The audible warning will sound once and the ORM warning lamp will flash as the
suspension lowers. The ECU energises the air control valves and the exhaust valve to release air pressure from the
air springs. When standard ride height is reached the ORM warning lamp will extinguish and the ECU will de-energise
the air control valves and the exhaust valve solenoids.
If the SLS is in ORM and the vehicle speed exceeds 18 mph (30 km/h), the ECU will lower the SLS to standard ride
height. The driver will be informed of this by an audible warning and the ORM warning lamp flashing as the suspension
lowers. When normal ride height is achieved, the ORM warning lamp will extinguish.
At sea level, the time to change the SLS from normal ride height to ORM or visa versa will take between 15 and 20
seconds.
If the ECU determines that conditions are not correct for SLS operation, i.e.; axle articulation or system fault, the
audible warning will sound three times to inform the driver that the ORM request has not been granted.
Extended mode
The extended mode is automatically operated by the ECU and requires no input from the driver. Extended mode
operates when the chassis is grounded causing the rear wheels to spin. This information is generated by the ABS
function of the SLABS ECU.
When the ECU senses that the chassis is grounded and the vehicle speed is less than 6 mph (10 km/h), the ECU will
operate the compressor and energise the air control valves for 25 seconds to raise the rear of the vehicle. This
operates irrespective of the mode that the SLS system is in at that time. To inform the driver, the ORM warning lamp
will flash continuously at all times that the system is in extended mode.
The driver can exit the extended mode by depressing the ORM switch for not less than 0.5 seconds or by exceeding
8 mph (13 km/h).
Remote handset SLS control
The remote handset is an accessory item which allows the SLS to be operated between normal ride height and bump
stop height to allow easier connection and disconnection of trailers. The remote handset is similar in appearance to
that of the remote door locking handset but does not have an integral key. A circular button with an arrow is used to
raise the SLS and an oval button with the 'Land Rover' logo is used to lower the SLS.
The remote handset control requires all doors to be closed and the ignition to be in position II, but the engine does
not need to be running.

REAR SUSPENSION
64-22 DESCRIPTION AND OPERATION
Pressing the lower button will signal the SLABS ECU, via the RF receiver and the BCU, to energise the exhaust valve
and air control valves. The SLS will lower up to 60 mm (2.36 in) below normal ride height if the button is held. If the
button is released the SLS will stop at that point.
Pressing the raise button will signal the SLABS ECU, via the RF receiver and the BCU, to start the compressor and
energise the exhaust valve and air control valves. The SLS will raise to normal ride height if the button is held. If the
button is released the SLS will stop at that point.
When raising or lowering the SLS using the remote handset, the SLS warning lamp will flash and the audible warning
will sound when the system is operating. When the SLS is fully lowered the warning lamp will stay illuminated. The
SLS will reset to normal ride height if the vehicle speed exceeds 3 mph (5 km/h) for 10 seconds when the SLS is
lowered.
Transportation mode
Transportation mode must be used when the vehicle is transported on a trailer and secured by the chassis. The
transportation mode can only be enabled and disabled with TestBook.
The transportation mode lowers the rear suspension onto the bump stops with the engine not running. When the
suspension is in transportation mode, the SLS warning lamp is continuously illuminated when the ignition is in position
II.
When the engine is started in transportation mode, the SLS system will raise the rear suspension until a gap of 25
mm (1 in.) exists between the bump stop and the axle. The SLS warning lamp will flash continuously while the SLS
system is raising the suspension. When the gap between the bump stop and the axle is achieved, the warning lamp
will illuminate continuously.
When TestBook is used to disable the transportation mode, the rear suspension will raise to normal ride height when
the engine is running.

BRAKES
DESCRIPTION AND OPERATION 70-3
1ABS sensor
2ABS modulator
3Return pump relay
4SLABS ECU
5Brake lamp relay
6Centre high mounted stop lamp
7LH brake lamp
8RH brake lamp
9Instrument pack
10Body control unit
11Reverse lamp switch (manual gearbox)
12Diagnostic socket
13HDC switch
14Transmission high/low switch
15Centre differential lock switch
16Engine control module
17Battery power supply
18Ignition power supply

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 70-19
HDC switch
The HDC switch is a latching push switch installed on the fascia, in the switchpack inboard of the steering wheel.
When pushed in, the switch connects an ignition supply to the SLABS ECU to initiate HDC.
Warning indications
The SLABS ECU operates audible and visual warnings to convey brake system status.
Audible warning
A repetitive chime, at a frequency of 2 Hz, draws attention to warning lamp indications. The chime is produced on the
speaker in the instrument pack.
Warning lamps
1ABS warning lamp
2HDC fault warning lamp
3ETC warning lamp
4HDC information warning lamp
5Brake warning lamp (all except NAS)
6Brake warning lamp (NAS only)
The following brake system warning lamps can be found in the instrument pack:
lA red brake graphic (all except NAS vehicles) or red BRAKE legend (NAS vehicles), to warn of low brake fluid
level, handbrake on and brake control system failure affecting EBD.
lAn amber ABS graphic, to warn of brake control system failure affecting the ABS function.
lAn amber TC graphic, to warn of brake control system failure affecting the ETC function.
lTwo inclined vehicle graphics, one amber (fault) and one green (information), to indicate operating status of HDC
and to warn of brake control system failure affecting the HDC function.
Each warning lamp is illuminated by a separate LED. The ABS, brake and ETC warning lamps are continuously on
while illuminated; the two HDC warning lamps are either continuously on or flash at a frequency of 2 Hz while
illuminated.