2002 LAND ROVER DISCOVERY abs

AIR CONDITIONING
82-26DESCRIPTION AND OPERATION
The rear evaporator/blower assembly cools and dehumidifies air from the cabin and supplies it to the rear distribution
system. The unit is installed on the left side of the loadspace, behind the quarter trim. A grille in the quarter trim allows
air to flow from the loadspace into the evaporator/blower. Refrigerant lines for the evaporator and a condensate drain
tube are attached to the rear floor.
The evaporator and blower are installed in a common housing, which also incorporates the resistor pack for the
blower. A thermostatic expansion valve is integrated into the inlet refrigerant line. A rear blower relay is attached to
the top of the housing.
Evaporator
The evaporator absorbs heat from the recirculated air being supplied to the distribution ducts.
Thermostatic expansion valve
The thermostatic expansion valve meters the flow of refrigerant into the evaporator to match the heat load of the air
passing through the evaporator matrix. A capillary tube, attached to the outlet pipe of the evaporator and connected
to the thermostatic expansion valve, automatically adjusts the valve opening in relation to the refrigerant temperature
at the evaporator outlet.
Blower
The blower controls the volume of air being supplied to the distribution outlets. The blower is an open hub, centrifugal
fan powered by an electric motor. A dust filter is installed over the fan inlet. The blower switch on the control panel
and the resistor pack control the operation of the blower, which can be selected to run at one of four speeds.
Resistor pack
The resistor pack supplies reduced voltages to the blower motor for blower speeds 1, 2 and 3. For blower speed 4,
the resistor pack is bypassed and battery voltage drives the motor at full speed. The pack is installed in the air outlet
from the blower fan, so that any heat generated is dissipated by the air flow.
Distribution system
Air ducts
Ducts connected to the rear evaporator/blower motor assembly distribute air to five vent assemblies in the roof.
Vent assemblies
The vent assemblies allow occupants to control the flow and direction of air. Each vent assembly incorporates a
thumbwheel to regulate flow and moveable vanes to control direction.
Rear control system
The control system operates the blower to control the operation of the rear A/C. The control system consists of two
control switches and a rear blower relay.
Control switches
A rear A/C switch and a blower speed switch are installed on a control panel in the roof lining. The A/C switch is a
latching pushswitch with an amber indicator lamp which illuminates when rear A/C is selected on. The blower speed
switch is a slide switch with a positive detent at each of four speed positions (there is no off position).
Rear blower relay
The rear blower relay controls the electrical supply to the blower.

AIR CONDITIONING
DESCRIPTION AND OPERATION 82-27
Operation
The rear A/C only operates if the front A/C is on to pump refrigerant through the rear evaporator/blower assembly.
When the rear A/C switch is selected on, the indicator lamp in the switch illuminates and the rear blower relay is
energised. The rear blower relay switches battery power to the blower motor, which runs at the speed selected on the
blower speed switch.
The air from the blower passes through the evaporator matrix, which absorbs heat from the air. The cooled air is then
supplied to the roof vents through the distribution ducts. The heat absorbed by the refrigerant in the evaporator is
sensed by the thermostatic expansion valve. The thermostatic expansion valve then opens and regulates the flow of
refrigerant through the evaporator in proportion to the amount of heat being absorbed from the air.
When the rear A/C switch is selected off, the blower stops. The thermostatic expansion valve senses the subsequent
decrease in temperature of the refrigerant in the evaporator. The thermostatic expansion valve then closes and stops
the flow of refrigerant, except for a minimal bleed flow.

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-1
BODY CONTROL UNIT DESCRIPTION AND OPERAT ION
Description
General
The Body Control Unit (BCU) is located behind the passenger glovebox and is connected to the main harness by four
connectors on its bottom edge and an additional connector located on the side of the BCU casing. Mounting the BCU
behind the fascia makes it reasonably inaccessible for intruders to disable the anti-theft system.
The BCU uses solid-state microprocessor control to perform logical operations and timing functions for a variety of
the vehicle's electrically operated systems, these include:
lDoor locking.
lAnti-theft alarm and immobilisation system.
lExterior lighting including direction indicators and hazard warning lamps.
lCourtesy lighting.
lWipers and washers.
lElectric windows and sunroof.
lHeated windows.
The BCU also communicates with several other electronically controlled systems such as the EAT ECU and SLABS
ECU and also has a datalink between the Intelligent Driver Module (IDM) and the instrument pack. The datalink is a
low speed bus capable of transmitting and receiving messages at a data rate of 10,400 bits per second. Additional
inputs and outputs to peripheral devices are included which are necessary for determining vehicle status for particular
logical operations e.g. crank, ignition key inserted, fuel flap enable etc.
The BCU receives its power supply from the engine compartment fuse box, and is protected by a 10 A fuse.
The BCU communicates with the IDM to provide the control signals to perform power switching operations in
conjunction with dedicated relays.
IDM
The IDM is integrated into the passenger compartment fuse box, which is mounted behind the fascia below the
steering column. There are no harnesses between the fuse box and the IDM. The IDM performs the power switching
operations for several of the vehicle's electrical systems.
The IDM communicates with the BCU and the instrument pack via a serial interface. If the BCU or the IDM is replaced,
the communications link between the two units has to be re-established. This can be done either by switching on the
ignition and leaving it on for five minutes, or by using TestBook. The vehicle immobilisation will remain active until the
communications link between the BCU and IDM has been re-established.
Transit mode
To prevent excessive battery drain during transit to overseas markets, the vehicle is placed in a transit mode. The
following functions are disabled when the vehicle is in transit mode:
lVolumetric sensors.
lPassive immobilisation.
lImmobilisation of the vehicle by use of door lock.
lIgnition key interlock.
lElectric seat enable time-out with driver's door open.

BODY CONTROL UNIT
86-3-18 DESCRIPTION AND OPERATION
Self levelling suspension and ABS
The BCU communicates with the SLABS ECU for several functions:
lAn output is provided from the SLABS ECU to the BCU to provide the logic conditions for issuing the SLS audible
warning.
lThe BCU receives an input from the SLABS ECU relating to the raise/ lower command from the remote handset.

+ REAR SUSPENSION, DESCRIPTION AND OPERATION, Description - SLS.
Hill descent control
The BCU provides an output signal to the SLABS ECU for automatic transmission in neutral for HDC control. The
BCU checks the status of the ignition and 'gearbox state' inputs and provides a 'Neutral selected' output. If the ignition
is on and 'gearbox state' is Neutral, the 'Neutral selected' output is on, otherwise 'Neutral selected' is off.

+ BRAKES, DESCRIPTION AND OPERATION, Description.
Heated screens
The Heated Front Screen (HFS) is fitted for some market destinations and is operated from a non-latching switch
located on the instrument pack cowl. The BCU will only allow the heated front screen to operate when the engine is
running and controls the time-out period for switching the circuit off.
The heated front screen operation can also be controlled from the Automatic Temperature Control (ATC) ECU on
vehicles fitted with air conditioning.
The heated rear window will only function when the engine is running, and is operated by a non-latching switch on the
instrument pack cowl. The heated rear window can also be operated by the ATC ECU on vehicles fitted with air
conditioning.
Interior courtesy lamps
The BCU controls the operation of the interior courtesy lamps. The courtesy lamps are situated in the front, mid and
rear areas of the headlining.
Fuel flap actuator
The BCU provides an earth path to the fuel flap release solenoid to allow the fuel filler flap to be opened. This is only
allowed if the alarm system is not set and all other conditions have been satisfied. The fuel flap release switch is
located in the fascia switch pack and it receives a voltage supply from the passenger compartment fuse box.
Audible warnings
The BCU can request the instrument pack to generate an audible warning in response to conditions it has detected
and which need to be drawn to the driver's attention. One of six different audible warnings can be requested by the
BCU.
Sound request number Sound functions Priority (1 = lowest, 6 = highest)
0Off 1
1 Seat belt warning 6
2 Key-in warning 3
3 SLABS/ HDC warning 4
4 Transfer box in neutral warning 5
5 Lights on warning 2

BODY CONTROL UNIT
86-3-36 DESCRIPTION AND OPERATION
Key-in warning
The BCU can be programmed to one of two options:
lOption 1 – no timeout.
lOption 2 – no key-in warning.
The BCU issues an audible warning No. 2 request, depending on the status of the following inputs:
lIgnition state.
lIgnition key inserted.
lDriver's door open.
If the key-in warning is programmed into the BCU for operation, audible warning No.2 will be requested if the ignition
switch is off, the ignition key inserted signal is on and the driver's door open signal is ON.
In the event of a communications link failure occurring, the audible warning request is not sent to the instrument pack.
SLABS HDC warning
The BCU issues an audible warning No. 3 request, depending on the status of the following inputs:
lIgnition state.
lSLABS HDC warning.
The SLABS warning transmitted by the SLABS ECU is a 2 Hz signal, audible warning No. 3 is requested on every
falling edge of this signal. If the signal from the SLABS ECU stays low for more than 650 ms, audible warning No. 3
is requested every 2 seconds, for 30 seconds, while the signal stays low.
In the event of a communications link failure occurring, the audible warning request is not sent to the instrument pack.
Transfer box in neutral warning
If the transfer box is in the neutral position and the ignition switch is on, the BCU issues an audible warning No. 4
request. The BCU checks for the following inputs:
lTransfer box neutral selected.
lIgnition on.
The transfer box in neutral warning is activated by communicating with the instrument pack via the serial datalink. If
a communications link failure occurs while the transfer box in neutral warning is active, the audible warning will not
operate.
Lights on warning
If the ignition switch is off while the side lamps or headlamps on and the driver's door is opened, the BCU issues an
audible warning No. 5 request.
The BCU checks for the following inputs:
lDriver's door open.
lIgnition on.
lSide lamps.
lDipped beam state.
lMain beam state.
The lights on warning is activated by communicating with the instrument pack via the serial datalink. If a
communications link failure occurs while the lights on warning is active, the audible warning will not operate.

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-37
SLABS raise/lower
Before enabling a SLS vehicle raise/ lower request, the BCU checks the logical condition of the following inputs:
lIgnition state.
lSLABS raise request.
lSLABS lower request.
If the ignition switch is in position 0 or I, the vehicle raise/ lower request is off.
With the ignition switch in position II, and the 'SLABS raise' request and 'SLABS lower' request both off, the vehicle
raise/ lower request output is driven at 25 Hz with a 50% duty cycle and the vehicle height remains unchanged.
If the 'SLABS lower' request input is on, the vehicle raise/lower request output is driven at 25 Hz with a 25% duty cycle,
lowering the vehicle.
If the 'SLABS raise' request input is on, the vehicle raise/lower request output is driven at a 25 Hz with a 75% duty
cycle.

IN CAR ENTERTAINMENT
DESCRIPTION AND OPERATION 86-6-3
High line ICE system control diagram
1Fusible link
2Battery power supply fuse
3Remote radio control switches
4Radio cassette
5CD-autochanger
6Telephone system interface
7Speed signal from SLABS ECU
8Speakers
9Power amplifier10Auxiliary power supply fuse
11Auxiliary relay
12Radio headphone amplifier RH rear
13Radio headphone amplifier LH rear
14Amplifier FM aerial
15FM aerial
16Amplifier AM/FM aerial
17AM/FM aerial

IN CAR ENTERTAINMENT
DESCRIPTION AND OPERATION 86-6-11
If one headphone amplifier unit has control of the tape player, CD or radio, the other headphone amplifier will be able
to listen and be able to change tape tracks or radio bands. Other buttons allow a search seek function of radio band
or compact disk track, reversal of the tape, radio station and volume adjustment depending on the current operating
mode. If one radio headphone amplifier has control of the radio, tape or CD autochanger the other radio headphone
amplifier is able to change the track or radio band selected. A headphone socket with a glow ring is located on the
control panel. When a headphone is turned on , a 'headphone-module active' signal is sent to the radio cassette
player. The design incorporates panel illumination and a glow-ring to locate the socket in low light conditions. To
control the audio output from the radio headphone amplifiers, signals are sent to and received from the radio cassette
player.
Automatic volume control (High line system only)
An automatic base and treble volume control feature compensates for increases in interior road/transmission noise.
A road speed signal is monitored by the power amplifier, the signal is supplied by the SLABS ECU.

+ BRAKES, DESCRIPTION AND OPERATION, Description.The power amplifier boosts the levels of base
and treble as road speed increases. This system ensures that the apparent volume of sound remains constant and is
not affected by increases in the background noise in the vehicle.
Speakers
Some vehicles will not have all the speakers, the type and location of speakers fitted depends on the trim level and
ICE options specified for the vehicle.
A-post speakers LH/RH (if fitted)
The A-post speakers are located in the A-post trim on each side of the windscreen, and are each protected by a metal
grille. The speakers are held from the rear by a bayonet clip that clamps the speaker on to the A-post trim. The A-post
speakers are a high range type and have a power rating of:
lMid line system A-post speakers have a power rating of 15 watts and an impedance of 4
Ω.
lHigh line system A-post speakers have a power rating of 30 watts and an impedance of 4
Ω.
Upper front and rear door speakers LH/RH (high line system only)
The upper door speakers are located in the upper door trim, the speaker is protected by an integral metal grille. The
speaker is held in by a threaded ring that clamps the speaker from the rear onto the door trim. The upper door speaker
is a mid-range type and has a power rating of 30 watts and an impedance of 4
Ω.
Lower front door speakers LH/RH
The lower front door speaker is located in the front end of the lower (pocket) trim and is secured by three self tapping
screws. The speaker is protected by a clip on circular metal grille. The type of lower front door speakers fitted depends
on trim level and market:
lThe base and mid line systems are fitted with full-range door speakers with a power rating of 15 watts and an
impedance of 4
Ω
lThe high line system is fitted with a low-range door speaker with a power rating of 30 watts and an impedance
of 4
Ω.
Lower rear door speaker LH/RH
The lower rear door speaker is located in the lower door trim and is secured by three self tapping screws. The speaker
is protected by a clip on metal grille. The type of lower rear door speaker fitted depends on trim level and market:
lThe base and mid line systems are fitted with full-range door speakers with a power rating of 15 watts and an
impedance of 4
Ω
lThe high line system is fitted with a low-range door speaker with a power rating of 30 watts and an impedance
of 4
Ω.
Low range tail door speakers (high line system only)
The low range tail door speaker are located in a plastic casing in the lower door trim. Each of the two speakers is
secured to the casing with four self tapping screws. The casing is secured to the lower door structure with eight bolts.
The tail door trim surrounds the casing, the front of the casing is covered by a metal grill that is secured with six
screws. The low range tail door speakers have a power rating of 30 watts and has an impedance of 4
Ω.