2002 LAND ROVER DISCOVERY traction control

INTRODUCTION
01-3
Abbreviations and Symbols
A Amperes
AAP Ambient Air Pressure
AAT Ambient Air Temperature
ABDC After Bottom Dead Centre
ABS Anti-Lock Brake System
ABS / TC Anti-lock Brake System / Traction
Control
ac Alternating current
A/C Air Conditioning
ACE Active Cornering Enhancement
ACEA Association of Constructors of
European Automobiles
AFR Air Fuel Ratio
AP Ambient Pressure
ASC Anti-shunt Control
ATC Air Temperature Control
ATDC After Top Dead Centre
AUX Auxiliary
AVC Automatic Volume Control
BBDC Before Bottom Dead Centre
BBUS Battery Backed Up Sounder
BCU Body Control Unit
BDC Bottom Dead Centre
bhp Brake Horse Power
BP Boost Pressure
BPP Brake Pedal Position
BS British Standard
BTDC Before Top Dead Centre
BWD Backward
C Celsius
CAN Controller Area Network
CD Compact Disc
CDC Centre Differential Control
CDL Central Door Locking
CD - ROM Compact Disc - Read Only
Memory
CFC Chlorofluorocarbon
CHMSL Centre High Mounted Stop Lamp
CKP Crankshaft Position
CLV Calculated Load Value
cm Centimetre
cm
2Square centimetre
cm3Cubic centimetre
CMP Camshaft Position
CPP Clutch Pedal Position
CO Carbon Monoxide
CO
2Carbon Dioxide
COB Clear Over Base
CR Common Rail
CVS Canister Vent Solenoid
dB Decibels
DDM Driver's Door Module
deg. Degree, angle or temperature
DI Direct Injection
dia. DiameterDIN Deutsche Industrie Normen
(German Industrial Standards)
dc Direct current
DCV Directional Control Valve
DOHC Double Overhead Camshaft
DSP Digital Signal Processing
DTI Dial Test Indicator
DMF Dual Mass Flywheel
DVD Digital Versatile Disc
EACV Electronic Air Control Valve
EAT Electronic Automatic
Transmission
EBD Electronic Brake pressure
Distribution
ECD European Community Directive
ECM Engine Control Module
ECT Engine Coolant Temperature
ECU Electronic Control Unit
EDC Electronic Diesel Control
EEPROM Electronic Erasable
Programmable Read Only
Memory
EGR Exhaust Gas Recirculation
EKA Emergency Key Access
ELR Emergency Locking Retractor
EN European Norm
EOBD European On Board Diagnostics
EON Enhanced Other Network
ERL Electrical Reference Library
ETC Electronic Traction Control
EUI Electronic Unit Injector
EVAP Evaporative Emission
EVR Electronic Vacuum Regulator
F Fahrenheit
ft. Feet
FBH Fuel Burning Heater
FET Field Effect Transistor
FIP Fuel Injection Pump
FTC Fast Throttle Control
FWD Forward
> Greater than
g Gramme or Gravity
gal. Gallons
GMT Greenwich Mean Time
GPS Global Positioning System
hHour
hc High compression
HC Hydro Carbons
HDC Hill Descent Control
HDOP Height Dilation Of Precision
HDPE High Density Polyethylene
HFS Heated Front Screen
Hg Mercury
HO
2S Heated Oxygen Sensor
HMW High Molecular Weight

TRANSFER BOX - LT230SE
DESCRIPTION AND OPERATION 41-15
High/low detect switch
A high/low detect switch is fitted in the front output housing and connects to earth when low is selected. The switch is
connected to the engine ECM, the SLABS ECU and the EAT ECU. The purpose of the switch is to enable selection
of the hill descent feature and to modify the engine fuelling and automatic gearbox gearshift maps stored within the
respective ECM's and ECU's.
Differential lock - Fitted to certain vehicles only
The differential lock selector housing is bolted to the top of the front output housing, the selector finger passes through
the housing, locating in a slot in the differential lock selector shaft. The differential lock selector shaft passes through
the selector fork which is located beneath a plate bolted to the side of the output housing. The selector fork engages
the dog clutch sleeve with the differential rear shaft when the splines of the sleeve and differential rear shaft are
aligned. A spring loaded detent ball fitted in the output housing locates in grooves in the shaft.
Functionality – Vehicles up to 03 model year only
The function of the differential lock used in previous applications is performed on this vehicle by the Electronic Traction
Control System. However, for the purposes of 2 wheel rolling road testing , the differential lock components are
retained. For all driving conditions however, the differential lock must be set in the unlocked position.
Up to 03 model year specification shown
The differential lock must only be engaged for 2 wheel rolling road testing as engagement of the lock disables the
traction control feature and inhibits correct operation of the electronic brake distribution and hill descent features. It
will also be necessary to disconnect the propeller shaft from the transfer box output shaft driving the axle whose
wheels are NOT on the rolling road. The lock may be engaged/disengaged by using a 10 mm open ended spanner
on the flats (arrowed) machined on the differential lock selector shaft.
Vehicles not fitted with a differential lock may be identified by there being no cover or selector shaft (arrowed) on the
front output housing.
WARNING: VEHICLES NOT FITTED WITH A DIFFERENTIAL LOCK MUST NOT BE TESTED ON A ROLLING
ROAD WHERE THE ROLLERS ARE DRIVEN BY THE VEHICLE.

TRANSFER BOX - LT230SE
41-16 DESCRIPTION AND OPERATION
Functionality – Vehicles from 03 model year only
The differential lock must be engaged for 2 wheel rolling road testing. It will also be necessary to disconnect the
propeller shaft from the transfer box output shaft driving the axle whose wheels are NOT on the rolling road. In
addition, the ETC system must be deactivated by either, removing a fuse (10A fuse 28 in the passenger compartment
fusebox, labelled ABS) or disconnecting the ABS modulator pump. This must be done with the ignition switched off.
Note that the SLABS ECU may record a system fault.
The lock can be engaged or disengaged using the selector lever. Vehicles not fitted with a differential lock can be
identified by a high/low range selector lever with no differential lock functionality and the cover and selector shaft
(arrowed), not visible on the front output housing.
WARNING: VEHICLES NOT FITTED WITH A DIFFERENTIAL LOCK MUST NOT BE TESTED ON A ROLLING
ROAD WHERE THE ROLLERS ARE DRIVEN BY THE VEHICLE.
Differential lock warning lamp switch - if fitted - Vehicles up to 03 model year
A differential lock warning lamp switch connected to the SLABS ECU and operated by movement of the selector fork
and shaft is screwed into the top of the output housing. The switch connects to earth when the differential lock is
engaged.
Differential lock warning lamp switches - if fitted - Vehicles from 03 model year
Vehicles from 03 model year are fitted with two differential lock warning lamp switches.
One switch is of a new design and is fitted into the top of the front output housing in the same position as on previous
models. The switch is connected to the SLABS ECU and is operated by movement of the selector fork and shaft.
The second switch is located in a threaded hole on the forward face of the front output housing. The switch is also
connected to the SLABS ECU and is operated by movement of the selector shaft.
Both switches have an aluminium washer which seals the switch to the casing and also sets the switch position,
removing the requirement for a setting procedure.
Both switches are connected in parallel to earth when the differential lock is engaged. This earth is sensed by the
SLABS ECU which illuminates the differential lock warning lamp in the instrument pack.
Differential lock warning lamp - Vehicles up to 03 model year – if fitted
The differential lock warning lamp is located in the instrument pack and provides a warning to the driver when the
ignition is switched on that the differential lock is engaged. The warning lamp illuminates in a Red colour.
With the lock engaged, the traction control and electronic brake distribution warning lamps will also be illuminated.
Disengagement of the differential lock should be carried out with the ignition switched off. The warning lamps must
be extinguished when the ignition is switched on again.
Differential lock warning lamp – vehicles from 03 model year – if fitted
The differential lock warning lamp is located in the instrument pack and provides a visual warning to the driver, when
the ignition is on, the differential lock is engaged. The warning lamp illuminates in an amber colour.
When the lock is engaged, the warning lamp is illuminated and the instrument pack sounder emits three audible
chimes. When the lock is disengaged, the warning lamp is extinguished and the instrument pack sounder emits three
audible chimes.
Rear output housing
The rear output housing carries the output shaft and flange. A cable operated transmission brake is attached to the
housing, the brake drum being attached to the output flange.
The rear output shaft is supported in the housing by a single bearing and is splined into the differential rear sun gear.

BRAKES
DESCRIPTION AND OPERATION 70-5
Description
General
The brakes consist of front and rear disc brakes operated by a diagonally split, dual circuit hydraulic system with
vacuum servo power assistance. The system incorporates the following control functions as standard on all models:
lAnti-lock Brakes (ABS), to prevent road wheels locking during brake application.
lElectronic Brake Distribution (EBD), to control distribution of hydraulic pressure between front and rear axles.
Replaces mechanical pressure limiting valve of previous systems.
lElectronic Traction Control (ETC), to maintain even torque distribution to the road wheels.
lHill Descent Control (HDC), to provide controlled descent ability in off road conditions.
Hydraulic system schematic
1Master cylinder/brake servo assembly
2Brake pedal
3ABS modulator
4Rear brake
5Front brake
6Hydraulic circuit
aPrimary
bSecondary
For normal brake operation, brake pedal movement is assisted by the brake servo assembly and transmitted to the
master cylinder assembly. The master cylinder assembly converts brake pedal movement to hydraulic pressure.
Primary and secondary brake pipe circuits supply the hydraulic pressure to the brakes via the ABS modulator: the
primary circuit supplies the front left and rear right brakes; the secondary circuit supplies the front right and rear left
brakes. Vacuum for the brake servo assembly is obtained from the engine inlet manifold (V8 models) or a vacuum
pump (diesel models), through a vacuum line and non return valve. To reduce operating noise, sleeving is installed
on some of the brake pipes in the engine compartment and the pipes are located in sprung pipe clips.

BRAKES
70-14 DESCRIPTION AND OPERATION
The ABS modulator is a 4 channel unit that controls the supply of hydraulic pressure to the brakes in response to
inputs from the SLABS ECU. The modulator is attached by three mounting bushes to a bracket on the LH inner front
wing, and connected to the primary and secondary hydraulic circuits downstream of the master cylinder assembly.
Three electrical connectors link the ABS modulator to the vehicle wiring.
Passages within the ABS modulator, separated into primary and secondary circuits, connect to the various internal
components that control the supply of hydraulic pressure to the brakes:
lShuttle valves and non return valves control the flow through the internal circuits.
lShuttle valve switches, connected in series to the SLABS ECU, provide a brakes on/off signal.
lA damper chamber and restrictor are included in each circuit to refine system operation.
lInlet and outlet solenoid valves control the flow to the individual brakes.
lAn expansion chamber is connected to each circuit to absorb pressure.
lA return pump is connected to both circuits to provide a pressure source.
The ABS modulator has three operating modes: Normal braking, ABS braking and active braking.
Normal braking mode
When the brake pedal is pressed, pressurised fluid from the master cylinder assembly moves the shuttle valves to
open lines 'A' and close the shuttle valve switches. Pressurised fluid then flows through the open inlet solenoid valves
to operate the brakes. The closed shuttle valve switches supply a brakes on signal to the SLABS ECU. If the SLABS
ECU determines that EBD is necessary, it energises the inlet solenoid valves for the brakes of one axle. The inlet
solenoid valves close to isolate the brakes from any further increase in hydraulic pressure.
ABS braking mode
When in the normal braking mode, if the SLABS ECU determines that ABS braking is necessary, it energises the inlet
and outlet solenoid valves of the related brake and starts the return pump. The inlet solenoid valve closes to isolate
the brake from pressurised fluid; the outlet solenoid valve opens to release pressure from the brake into the expansion
chamber and the return pump circuit. The brake releases and the wheel begins to accelerate. The SLABS ECU then
operates the inlet and outlet solenoid valves to control the supply of hydraulic pressure to the brake and apply the
maximum braking effort (for the available traction) without locking the wheel.
Active braking mode
When ETC or HDC are enabled, and the SLABS ECU determines that active braking is necessary, it starts the return
pump. Hydraulic fluid, drawn from the reservoirs through the master cylinder, shuttle valves and lines 'B', is
pressurised by the return pump and supplied to lines 'A'. The SLABS ECU then operates the inlet and outlet solenoid
valves to control the supply of hydraulic pressure to the individual brakes and slow the wheel(s).

BRAKES
DESCRIPTION AND OPERATION 70-21
ETC
The ETC function uses brake intervention to prevent wheel spin and maintain even torque distribution to the wheels.
ETC is automatically enabled while the brakes are off at speeds up to 62.5 mph (100 km/h), and operates the brakes
either individually or in axle pairs:
lAt speeds up to 31.3 mph (50 km/h), ETC uses individual brake intervention to maintain even torque distribution
between wheels on the same axle.
lVehicles up to 03 model year – At speeds between 0 and 62.5 mph (0 and 100 km/h), ETC also uses brake
intervention in axle pairs to maintain even torque distribution between the front and rear axles. In effect, this mode
of operation replaces the centre differential lock of the transfer box which, although still incorporated, is non
operational under normal driving conditions.

+ TRANSFER BOX - LT230SE, DESCRIPTION AND OPERATION, Description. If the centre differential
lock is in the locked condition, the SLABS ECU illuminates the ABS and ETC warning lamps and inhibits the ETC
function (the ABS, EBD and HDC functions are retained, but at degraded performance levels).
lVehicles from 03 model year (with differential lock fitted) – At speeds between 0 and 62.5 mph (0 and 100
km/h), ETC uses brake intervention in axle pairs to maintain even torque distribution between the front and rear
axles. If the centre differential lock is in the locked condition, the differential lock warning lamp in the instrument
pack is illuminated. The ABS, EBD, ETC and HDC functions are retained, but with revised parameters to suit the
locked differential.
While the ETC function is enabled, if the SLABS ECU detects a wheel accelerating faster than the average, indicating
loss of traction, it operates the ABS modulator in the active braking mode. Depending on the vehicle speed, active
braking is employed for either the brake of the affected wheel or for both brakes on the affected axle, until all four
wheels are driven at approximately the same speed again. During active braking the SLABS ECU also illuminates the
ETC warning lamp, for a minimum of 2 seconds or for the duration that ETC is active. ETC operation is desensitised
during 'hard' cornering.
HDC
HDC uses brake intervention to provide a controlled descent ability in off road conditions when engine braking is
insufficient to maintain a comfortable speed. This allows the driver to leave HDC selected and to control the vehicle's
descent speed, down to the system's minimum target speed, using only the accelerator pedal. The HDC function is
selected on/off by a switch on the fascia. When selected on, HDC is enabled in all forward gears and reverse provided:
lVehicle speed is below 31.3 mph (50 km/h).
lThe transfer box is in low range.
lOn manual gearbox vehicles, the clutch is engaged.
When HDC is enabled, the HDC information warning lamp illuminates. If HDC is selected outside the above
conditions, the HDC information warning lamp flashes and the audible warning sounds continuously.
When HDC is enabled, the SLABS ECU calculates a target speed from the throttle position element of the engine data
input, and compares this with actual speed. If the actual speed is higher than the target speed, the SLABS ECU
operates the ABS modulator in the active braking mode to slow the vehicle down to the target speed. While the braking
force is being applied, the SLABS ECU also energizes the brake lamp relay to put the brake lamps on. Active braking
is discontinued while vehicle speed is below the target speed or if the foot brakes are applied. Applying the foot brakes
during active braking may result in a pulse through the brake pedal, which is normal.
During active braking, the brakes are operated predominantly on the wheels of the leading axle, but if that is not
sufficient to achieve the required deceleration the brakes of the trailing axle are also applied. The deceleration rate is
dependent on the speed differential between initial vehicle speed and the target speed. The deceleration rates are
relatively low at higher speed differentials, then progressively increase as vehicle speed approaches the target speed.
Anti-lock braking is also enabled during active braking, but at very low speeds some wheel lock can occur.
The target speed increases as the accelerator pedal is pressed, from a programmed minimum with the accelerator
pedal released, up to a maximum of 31.3 mph (50 km/h). For any given accelerator pedal position, while travelling
uphill or on level ground the target speed is always greater than the corresponding vehicle speed, which allows the
vehicle to be driven normally without HDC intervention. However, when travelling downhill, the gravitational effect on
the vehicle means that for any given accelerator pedal position the target speed is less than the corresponding vehicle
speed, and HDC intervenes to limit vehicle speed to the target speed.

INSTRUMENTS
DESCRIPTION AND OPERATION 88-1
INS TRUMENTS DESCRIPTION AND OPERAT ION
Instrument pack
1Hill descent control information warning lamp
2Overspeed warning lamp
3Brake system warning lamp
4Malfunction Indicator Lamp (MIL)
5Tachometer
6Direction indicator warning lamp
7Main beam warning lamp
8Direction indicator warning lamp
9Speedometer
10SRS warning lamp
11Off road mode warning lamp
12Glow plug warning lamp
13Trailer warning lamp
14Water in fuel filter warning lamp
15Transmission high temperature warning lamp
16Seat belt warning lamp17Fuel tank level gauge
18Low fuel level warning lamp
19LCD odometer/trip meter
20Anti-theft status warning lamp
21ABS warning lamp
22Gearbox manual/sport mode warning lamp
23Alternator charge warning lamp
24ACE warning lamp
25Oil pressure warning lamp
26SLS warning lamp
27Hill descent control warning lamp
28Engine coolant temperature gauge
29High coolant temperature warning lamp
30Traction control warning lamp
31Differential lock warning lamp
32Transfer box neutral warning lamp

INSTRUMENTS
DESCRIPTION AND OPERATION 88-5
Description
General
The instrument pack consists of four analogue dials, four warning lamp packs and a Liquid Crystal Display (LCD)
odometer.
The four dials are used to indicate:
lRoad speed.
lEngine speed.
lFuel tank level.
lEngine coolant temperature.
The dials are driven by a microprocessor from information received from the serial communication link. Information
input is received as either:
lDigital.
lAnalogue.
lPulse train.
lPulse Width Modulation (PWM).
The LCD provides information for:
lOdometer.
lTrip distance.
lSelected gear (on vehicles fitted with an automatic gearbox).
A trip reset button is provided to zero the trip display, this button also allows the selection of "miles" or "kilometres"
for the display. A photocell controls the illumination of the LCD, maintaining contrast of the display during ambient light
changes.
Within the four warning lamp packs there are 28 lamps. A long life bulb illuminates the high beam warning lamp and
the rest of the warning lamps are illuminated by Light Emitting Diodes (LED's). All warning lamp legends are invisible
until lit. When lit the symbols are illuminated on a black background.
The warning lamps illuminate in one of four colours. The colour indicates the level of importance to the driver, as
follows:
lRed = warning.
lAmber = caution.
lGreen = system operative.
lBlue = main beam operative.
The first warning lamp pack is located in the top left-hand side of the instrument pack and contains the following
warning lamps:
lTraction control warning lamp.
lTransfer box in neutral warning lamp.
lDifferential lock warning lamp
lOverspeed warning lamp (activated for gulf market only).
lBrake system warning lamp.
lHill Descent Control (HDC) information warning lamp.
lMalfunction Indicator Lamp (MIL)/ SERVICE ENGINE SOON warning lamp.
The second warning lamp pack is located in the centre of the instrument pack and contains the following warning
lamps:
lDirection indicator warning lamps.
lHigh beam warning lamp.
lAnti-lock brake system warning lamp.