ESP LAND ROVER DISCOVERY 2002 Manual PDF

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.

RESTRAINT SYSTEMS
75-22 REPAIRS
4.Release rotary coupler multiplug from bracket
and disconnect from harness.
5.Disconnect rotary coupler multiplug from
harness.
6.Remove rotary coupler.
Refit
1.Fit rotary coupler to steering column and
connect multiplug to harness.
2.Connect rotary coupler multiplug to harness
and secure to bracket.
3.Fit steering column nacelle.

+ STEERING, REPAIRS, Nacelle -
steering column.
4.Fit steering wheel.

+ STEERING, REPAIRS, Steering
wheel.
Airbag deployment tool - self test
$% 76.74.99
Test
1.Insert BLUE and YELLOW connectors of tool
lead into corresponding sockets on face of tool.
2.Connect crocodile clips of second tool lead to
battery, RED to positive and BLACK to
negative.
3.RED "READY" light should illuminate.
4.Press and hold both operating buttons.
5.GREEN "DEFECTIVE" light should illuminate.
6.Release both operating buttons.
7.RED "READY" light should illuminate.
8.Disconnect tool from battery.
9.Disconnect blue and yellow connectors from
tool face sockets.
10.Self test now complete.

CORROSION PREVENTION AND SEALING
CORROSION PREVENTION 77-4-7
The checks described above are intended to be visual only. It is not intended that the operator should remove trim
panels, finishers, rubbing strips or sound-deadening materials when checking the vehicle for corrosion and paint
damage.
With the vehicle on a lift, and using an inspection or spot lamp, visually check for the following:
lCorrosion damage and damaged paintwork, condition of underbody sealer on front and rear lower panels, sills
and wheel arches;
lDamage to underbody sealer. Corrosion in areas adjacent to suspension mountings and fuel tank fixings.
NOTE: The presence of small blisters in the underbody sealer is acceptable, providing they do not expose bare metal.
Pay special attention to signs of damage caused to panels or corrosion protection material by incorrect jack
positioning.
WARNING: It is essential to follow the correct jacking and lifting procedures.
With the vehicle lowered, visually check for evidence of damage and corrosion on all visible painted areas, in
particular the following:
lFront edge of bonnet;
lVisible flanges in engine compartment;
lLower body and door panels.
Rectify any bodywork damage or evidence of corrosion found during inspection as soon as is practicable, both to
minimise the extent of the damage and to ensure the long term effectiveness of the factory-applied corrosion
prevention treatment. Where the cost of rectification work is the owner's responsibility, the Dealer must advise the
owner and endorse the relevant documentation accordingly.
Where corrosion has become evident and is emanating from beneath a removable component (e.g. trim panel,
window glass, seat etc.), remove the component as required to permit effective rectification.
Underbody protection repairs
Whenever body repairs are carried out, ensure that full sealing and corrosion protection treatments are reinstated.
This applies both to the damaged areas and also to areas where protection has been indirectly impaired, as a result
either of accident damage or repair operations.
Remove corrosion protection from the damaged area before straightening or panel beating. This applies in particular
to panels coated with wax, PVC underbody sealer, sound deadening pads etc.
WARNING: DO NOT use oxy-acetylene gas equipment to remove corrosion prevention materials. Large
volumes of fumes and gases are liberated by these materials when they burn.
NOTE: Equipment for the removal of tough anti-corrosion sealers offers varying degrees of speed and effectiveness.
The compressed air-operated scraper (NOT an air chisel) offers a relatively quiet mechanical method using an
extremely rapid reciprocating action. Move the operating end of the tool along the work surface to remove the material.
The most common method of removal is by means of a hot air blower with integral scraper.
Another tool, and one of the most efficient methods, is the rapid-cutting 'hot knife'. This tool uses a wide blade and is
quick and versatile, able to be used easily in profiled sections where access is otherwise difficult.
Use the following procedure when repairing underbody coatings:
1Remove existing underbody coatings
2After panel repair, clean the affected area with a solvent wipe, and treat bare metal with an etch phosphate
material
3Re-prime the affected area
CAUTION: DO NOT, under any circumstances, apply underbody sealer directly to bare metal surfaces.
4Replace all heat-fusible plugs which have been disturbed. Where such plugs are not available use rubber
grommets of equivalent size, ensuring that they are embedded in sealer
5Mask off all mounting faces from which mechanical components, hoses and pipe clips, have been removed.
Underbody sealer must be applied before such components are refitted
6Brush sealer into all exposed seams
7Spray the affected area with an approved service underbody sealer
8Remove masking from component mounting faces, and touch-in where necessary. Allow adequate drying time
before applying underbody wax

CORROSION PREVENTION AND SEALING
77-4-8 CORROSION PREVENTION
After refitting mechanical components, including hoses and pipes and other fixtures, mask off the brake discs and
apply a coat of approved underbody wax.
NOTE: Where repairs include the application of finish paint coats in the areas requiring underbody wax, carry out paint
operations before applying wax.
Cavity wax injection
Areas treated with cavity wax are shown in the previous figures. After repairs, always re-treat these areas with an
approved cavity wax. In addition, treat all interior surfaces which have been disturbed during repairs whether they
have been treated in production or not. This includes all box members, cavities and door interiors. It is permissible to
drill extra holes for access where necessary, provided these are not positioned in load-bearing members. Ensure that
such holes are treated with a suitable zinc rich primer, brushed with wax and then sealed with a rubber grommet.
Before wax injection, ensure that the cavity to be treated is free from any contamination or foreign matter. Where
necessary, clear out any debris using compressed air.
Ensure that cavity wax is applied AFTER the final paint process and BEFORE refitting any trim components.
During application, ensure that the wax covers all flange and seam areas and that it is adequately applied to all
repaired areas of both new and existing panels.
It should be noted that new panel assemblies and complete body shells are supplied without wax injection treatment.
Ensure that such treatment is carried out after repairs.
Effective cavity wax protection is vital. Always observe the following points:
lComplete all paint refinish operations before wax application;
lClean body panel areas and blow-clean cavities if necessary, before treatment;
lMaintain a temperature of 18
° C (64° F) during application and drying;
lCheck the spray pattern of injection equipment;
lMask off all areas not to be wax coated and which could be contaminated by wax overspray;
lRemove body fixings, such as seat belt retractors, if contamination is at all likely;
lMove door glasses to fully closed position before treating door interiors;
lTreat body areas normally covered by trim before refitting items;
lCheck that body and door drain holes are clear after the protective wax has dried;
lKeep all equipment clean, especially wax injection nozzles.
Underbody wax
The underbody wax must be reinstated following all repairs affecting floor panels. The wax is applied over paints and
underbody sealers.
Remove old underbody wax completely from a zone extending at least 200 mm (7.874 in) beyond the area where new
underbody sealer is to be applied.
Engine bay wax
Reinstate all protective engine bay wax disturbed during repairs using an approved material.
Where repairs have involved replacement of engine bay panels, treat the entire engine compartment including all
components, clips and other fixtures with an approved underbonnet lacquer or wax.

+ BODY SEALING MATERIALS, MATERIALS AND APPLICATIONS, Approved materials.

HEATING AND VENTILATION
DESCRIPTION AND OPERATION 80-13
Operation
Air distribution
Turning the distribution knob on the control panel turns the control flaps in the heater assembly to direct air to the
corresponding fascia and footwell outlets.
Air temperature
Turning the LH or RH temperature knob on the control panel turns the related blend flaps in the heater assembly. The
blend flaps vary the proportion of air going through the cold air bypass and the heater matrix. The proportion varies,
between full bypass no heat and no bypass full heat, to correspond with the position of the temperature knob.
Blower speed
The blower can be selected off or to run at one of four speeds. While the ignition is on, when the blower switch is set
to positions 1, 2, 3, or 4, ignition power energises the blower relay, which supplies battery power to the blower. At
switch positions 1, 2 and 3, the blower switch also connects the blower to different earth paths through the resistor
pack, to produce corresponding differences of blower operating voltage and speed. At position 4, the blower switch
connects an earth direct to the blower, bypassing the resistor pack, and full battery voltage drives the blower at
maximum speed.
Fresh/Recirculated inlet air
When the recirculated air switch is latched in, the amber indicator LED in the switch illuminates and an earth is
connected to the recirculated air side of the fresh/recirculated air servo motor. The fresh/recirculated air servo motor
then turns the control flaps in the air inlet duct to close the fresh air inlet and open the recirculated air inlets.
When the latch of the recirculated air switch is released, the amber indicator LED in the switch extinguishes and the
earth is switched from the recirculated air side to the fresh air side of the fresh/recirculated air servo motor. The fresh/
recirculated air servo motor then turns the control flaps in the air inlet duct to open the fresh air inlet and close the
recirculated air inlets.
FBH system (where fitted)
The FBH system operates only while the engine is running and the ambient temperature is less than 5
°C (41 °F).
With the engine running and the ambient temperature below 5
°C (41 °F), the air temperature sensor connects the
alternator power supply to the ECU in the FBH unit. On receipt of the alternator power supply, the ECU starts the
circulation pump and, depending on the input from the temperature sensor in the heat exchanger, enters either a
standby or active mode of operation. If the heat exchanger casing temperature is 65
°C (149 °F) or above, the ECU
enters a standby mode of operation. If the heat exchanger casing temperature is below 65
°C (149 °F), the ECU enters
an active mode of operation. In the standby mode, the ECU monitors the heat exchanger casing temperature and
enters the active mode if it drops below 65
°C (149 °F). In the active mode, the ECU initiates a start sequence and
then operates the system at full or part load combustion to provide the required heat input to the coolant.
Start sequence
At the beginning of the start sequence the ECU energises the glow plug function of the glow plug/flame sensor, to
preheat the combustion chamber, and starts the combustion air fan at slow speed. After 30 seconds, the ECU
energises the FBH fuel pump at the starting sequence speed. The fuel delivered by the FBH fuel pump evaporates in
the combustion chamber, mixes with air from the combustion air fan and is ignited by the glow plug/flame sensor. The
ECU then progressively increases the speed of the FBH fuel pump and the combustion air fan to either part or full
load speed, as required by the system. Once full or part load speed is achieved, the ECU switches the glow plug/flame
sensor from the glow plug function to the flame sensing function to monitor combustion. From the beginning of the
start sequence to stable combustion takes approximately 90 seconds for a start to part load combustion and 150
seconds for a start to full load combustion.

AIR CONDITIONING
82-8DESCRIPTION AND OPERATION
Thermostatic expansion valve
Thermostatic expansion valve and evaporator
1Refrigerant outlet
2Refrigerant inlet
3Thermostatic expansion valve
4Evaporator
The thermostatic expansion valve meters the flow of refrigerant into the evaporator to match the refrigerant flow with
the heat load of the air passing through the evaporator matrix.
The thermostatic expansion valve is installed in the heater assembly, in the refrigerant inlet line to the evaporator.
Liquid refrigerant flows through the valve to the evaporator. The restriction across the valve reduces the pressure and
temperature of the refrigerant and changes it to a fine spray, which improves the evaporation process. Valve opening
is controlled by the pressure in a capillary tube containing a temperature sensitive fluid. One end of the capillary tube
is connected to a diaphragm housing on the thermostatic expansion valve, the other end of the capillary tube is sealed
and attached to the refrigerant outlet line of the evaporator. As the temperature of the refrigerant leaving the
evaporator changes, a corresponding change of capillary tube pressure and valve opening are produced. The warmer
the refrigerant leaving the evaporator becomes, the greater the volume of refrigerant allowed through the valve.

AIR CONDITIONING
82-18DESCRIPTION AND OPERATION
Operation
General
While the system is on, the ATC ECU operates the refrigerant system and the inlet air, blower speed, air temperature
and air distribution functions to produce the conditions requested on the control panel. When the system is first
switched on, the ATC ECU resumes the control outputs in use when the system was last switched off. If conditions
have changed, or a different mode is selected to switch the system on, the control outputs are then changed to
produce the required new settings.
The system operates in automatic, economy and defrost modes, with manual overrides of the inlet air source, blower
speed and air distribution. The air temperature is automatically controlled in all operating modes.
In the automatic mode, the ATC ECU operates the system to warm-up or cool down the cabin to establish and
maintain the temperature selections on the control panel, while directing the air to those outlets most comfortable for
the occupant(s). If a difference between the LH and RH temperature selections causes a conflict of the required inlet
air source, blower speed or air distribution settings, priority is given to achieving the temperature requested on the
driver's side of the control panel.
The ATC ECU enters the economy mode when the refrigerant compressor is selected off while the system is in the
automatic mode, which reduces the load on the engine. Economy mode operation is similar to the automatic mode,
but without the ability to cool the cabin if the ambient temperature is higher than the temperature selections made on
the control panel, or to dehumidify the air in the cabin.
In the defrost mode, the ATC ECU sets the inlet air source to fresh air, the blower to maximum speed, the air
distribution to windscreen and side windows, and outputs signals to the BCU to operate the rear window heater and
(where fitted) the windscreen heater. The BCU starts or, if the heaters are already on, resets the heater timers and
energises the rear window and windscreen heaters for a complete on cycle.
Air temperature control
To determine the amount of heat or cooling required by the cabin, the ATC ECU uses the sensor inputs and the
temperatures selected on the control panel to calculate target air outlet temperatures for the driver's and the front
passenger's side of the heater assembly. The ATC ECU then signals the servo motors controlling the respective blend
flaps in the heater assembly to move to the flaps to the appropriate position. The target temperatures are constantly
updated and, in the automatic mode, also used in further calculations to determine the inlet air source, the blower
speed and the air distribution.
Inlet air control
The inlet air source is automatically controlled while the system is off or on. While the system is on, the inlet air source
can also be manually controlled to give timed recirculated air or latched recirculated air.
While the system is off, the ATC ECU uses vehicle speed to determine the inlet air source. With the vehicle at rest,
the inlet air source is set to recirculated air. When vehicle speed reaches 17.5 mph (28 km/h), the inlet air source
changes to fresh air. The inlet air source then remains at fresh air until the vehicle speed decreases to 5 mph (8 km/
h), when it returns to recirculated air.
While the system is on, the ATC ECU uses the LH and RH temperature selections, vehicle speed, ambient air
temperature and coolant temperature to determine the inlet air source. In the automatic mode:
lIf one temperature selection is set to LO and one is set to a specific temperature or HI, the inlet air is set to
recirculated air.
lIf one temperature selection is set to HI and one is set to a specific temperature or HI, the inlet air is set to fresh
air.
lWhen specific LH and RH temperature selections are set, the inlet air source remains at fresh air except when
the air distribution function is set to face level only or face level and footwell outlets. If the air distribution function
is set to face level only or face level and footwell outlets, at 56 mph (90 km/h) the inlet air source changes to
recirculated air (to exclude ram effect, which becomes excessive at speed). When the vehicle speed decreases
to 37.5 mph (60 km/h), the inlet air source returns to fresh air.

BODY CONTROL UNIT
86-3-2 DESCRIPTION AND OPERATION
Power supply
Battery supply to the BCU and the IDM is provided through a 10 A fuse located in the engine compartment fuse box.
The BCU unit receives an ignition switched power supply (ignition switch position II) input via a 10 A fuse in the
passenger compartment fuse box.
The BCU receives a signal when the ignition switch is turned to the crank position, it then supplies an earth path to
the starter relay coil, to enable the crank operation by supplying power through the starter relay contacts to the starter
motor.
Battery voltage is monitored and BCU operation will function normally between 8 and 18 volts. Between 5.7 and 8
volts the BCU is in the 'under volts' state. The status of the battery is used to determine which outputs may be driven.
If a voltage supply above 18 volts is experienced, outputs will not normally be driven except for those functions which
are required during cranking (robust immobilisation, antenna coil, crank enable relay and feed to gear position switch
contacts W, X, Y, Z). In the over voltage state the vehicle can be driven, but all other functions are disabled and
outputs are switched off (power windows, heated screen, direction indicators etc.).
All functions are disabled on power up until communications between the BCU and IDM have been established. If
communications cannot be established, operation will commence with degraded functionality.
Battery supply to the IDM is provided through the inertia switch and a 10 A fuse in the engine compartment fuse box.
If the inertia switch contacts are closed battery voltage is available at the IDM; if the inertia switch contacts are open
there is no battery supply to the IDM. The supply condition of the IDM is signalled to the BCU via the serial bus. If the
inertia switch is operated (contacts open) the change in state is detected by the BCU which unlocks the doors if the
ignition switch is in position II and the alarm is not set.
The BCU is earthed through a hard-wire connection.
Inputs and outputs
The BCU and IDM process inputs and provide the necessary outputs for control and operation of the vehicle's 'body'
systems.
BCU inputs
The BCU processes signals received from the following components:
lDoor latch switches.
lDriver's door key lock/ unlock switches.
lBonnet activated security system.
lVolumetric sensors.
lCentral Door Locking (CDL) switches.
lRemote transmitter (via receiver unit).
lInertia fuel cut-off switch.
lIgnition switch.
lFuel flap release switch.
The input voltages (V
in) for BCU digital signals are defined as follows:
lLogic 1 when V
in ≥ 6V.
lLogic 0 when V
in ≤ 2V.
BCU input voltages between 2 and 6 volts are indeterminate and cannot be guaranteed.
Analogue input voltages are measured as a ratio with respect to battery voltage.

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-15
The BCU controls the wiper motor frequency of operation via the IDM when intermittent wipe or wash is selected. The
front intermittent wipe option features five different intermittent delay periods. The shortest delay period is 3 seconds
and this is increased by 2 second increments up to a maximum delay of 11 seconds. The desired delay period for the
front wipers is set by the position of the rotary switch located on the wiper column stalk.
The rear wiper switch is located on the instrument pack cowl and is latched when pressed. The rear wiper electric
motor is located in the tail door. The rear wiper operation is controlled according to a programmed strategy via the
BCU and the IDM. The BCU also checks for a signal from either the reverse lamp switch located in the vehicle gearbox
(manual gearbox models) or the gear position switch (automatic gearbox models) for operating the rear wipers when
the vehicle is in reverse. The rear wiper and washer only operate when the ignition switch is in position II.
The front and rear washer pumps and the headlamp powerwash (where fitted) are also controlled through the BCU.
The washers are operated from electric pumps attached to the washer reservoir located in the left hand wheel arch.
The front wash switch is located on the wiper column stalk and is pulled towards the steering wheel to select the
washer function. When the front washers are operated, the wipers are also activated for three full cycles. The rear
wash switch is located on the instrument pack cowl. The BCU programme can be configured in one of two modes of
operation:
lNo wiper operation when the wash switch is pressed.
lWiper action after an initial delay of 400 ms.
Headlamp wash is activated by the BCU via the IDM and operates when the headlamps are on and the front washers
function is selected.
Electric seats
The BCU controls the logical operation of the electrically operated front seats. Two modes of operation are available:

+ SEATS, DESCRIPTION AND OPERATION, Description - electric seats.
lElectric seat adjustment is enabled if the ignition is on or the driver's door is opened for a short time period.
lElectric seat adjustment is enabled if the ignition is on and the driver's door is closed.
The seats are operated by four electric motors which control the seat cushion rear up/ down, the seat cushion front
up/ down, seat cushion forward/ rearward and seat squab recline. The electrically powered lumbar adjustment in each
seat is operated by a single motorised air pump and a solenoid located on the seat squab frame. The air pump inflates
a cushion in the seat squab and the solenoid operates a valve to deflate the cushion. The seat squab and cushion
may also contain heater elements to provide heated seat operation.
The switches for electrically operated seats are located either side of the centre console.
Direction indicators and hazard warning lamps
The direction indicator lamps are operated from a three position direction indicator switch on the left hand, steering
column stalk. The BCU only allows the lamps to work as direction indicators when the ignition switch is in position II.
The BCU also controls the lamps to operate as hazard warning lamps and as a visual warning for the anti-theft system,
in which cases all lamps flash simultaneously irrespective of the ignition switch position.
System control of the direction indicators and hazard warning lamps is provided by the BCU operating with the IDM
and two electronic relays located in the passenger compartment fuse box. The IDM and relays are integral parts of
the passenger compartment fuse box and cannot be serviced individually. The serial data bus is used for
communication of status and operation requests between the BCU, IDM and instrument pack.
The hazard warning lamps are operated from a latching pushbutton switch located on the fascia.
All direction indicator/ hazard warning lamp bulbs are rated at 5 Watts.

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-17
Ignition key interlock (where fitted)
On automatic gearbox models, the ignition key interlock solenoid prevents removal of the ignition key from the ignition
switch when the transmission gear selector is not in the Park position. The logic control operation for this is performed
by the BCU.
Transfer box interlock (where fitted)
On automatic gearbox models, a transfer box interlock solenoid is controlled by the IDM to prevent transfer box shift
lever being moved out of high or low range unless certain conditions have been satisfied. The IDM controls the
operation of the transfer box relay which is located in the passenger compartment fuse box.

+ TRANSFER BOX - LT230SE, DESCRIPTION AND OPERATION, Description.
Gear position switch
A gear position switch is located on the automatic gearbox and is used to inform the BCU of the gear selector lever
position. The BCU has four sensing inputs from the gear position switch contacts W, X, Y, Z, which are used to
determine the gearbox drive status at any particular instance. The BCU gives an output corresponding to the gearbox
status derived from the gear position switch inputs. The logic states defining the gear selector positions are listed in
the table below, where Z1, Z2, Z3 and Z4 represent intermediate states which exist as the selector lever position is
changed:
The existence of an intermediate state causes a fault code to be detected by the BCU. To reduce the chances of the
fault condition occurring while changing selector lever position, the inputs are debounced and only considered valid
when they have existed for at least 33 ms.
Transmission neutral selector
The transmission neutral sensor provides an earth signal to the BCU when the transfer box is in neutral. The earth
signal causes the BCU to operate an audible warning when the transfer box is in neutral with the ignition switched on.

+ TRANSFER BOX - LT230SE, DESCRIPTION AND OPERATION, Description.
Gear position Switch contacts
WX Y Z
P (Park) 1 0 0 0
Z11100
R (Reverse) 0 1 0 0
Z11100
N (Neutral) 1 1 1 0
Z21010
D (Drive) 1 0 1 1
Z31111
30111
Z40011
20001
Z40011
10010