2002 LAND ROVER DISCOVERY relay

WIPERS AND WASHERS
DESCRIPTION AND OPERATION 84-15
Headlamp powerwash pump
The headlamp power wash pump consists of a DC motor with an impeller. It is located on the front of the washer fluid
reservoir.
The BCU controls operation of the headlamp power wash relay, which supplies battery voltage from fuse 4 located in
the engine compartment fuse box to the headlamp power wash pump. When the BCU determines headlamp power
wash is to be activated, it provides a ground path for the coil of the headlamp power wash relay. The auxiliary relay
located in the engine compartment fuse box supplies the headlamp power wash relay coil with battery voltage.

WIPERS AND WASHERS
84-16 DESCRIPTION AND OPERATION
Operation
Front intermittent wipe variable delay
The front intermittent wipe variable delay operation allows the driver to adjust the interval between wipes to suit local
conditions. Front variable delay operation activates when the following conditions are met:
lIgnition switch in position I or II.
lFront wash/ wipe switch is in the intermittent position.
The BCU receives the front intermittent wipe signal from the front wash/ wipe switch. The BCU receives a separate
signal from the variable delay switch, determines the delay interval from the front wash/ wipe switch position and
passes it on to the IDM. The IDM energises the front wiper relay to activate the front wiper motor.
If the delay duration is decreased during front variable delay operation, the wipers immediately operate once and then
the delay cycle is reset to the new duration.
If the delay duration is increased during front variable delay operation, the delay cycle is automatically increased by
the BCU.
Front low speed
Front low-speed operation activates when the following conditions are met:
lIgnition switch is in position I or II.
lFront wipe/ wash switch is in low speed position.
Selecting low-speed on the front wash/ wipe switch signals the IDM to energises the front wiper relay, which provides
power to the front wiper motor assembly.
Front high speed
Front high-speed operation activates when the following conditions are met:
lIgnition switch is in position I or II.
lFront wipe/ wash switch is in high speed position.
Selecting high speed on the front wash/ wipe switch allows power to flow from the switch directly to the wiper motor.
The high-speed input goes to a set of brushes in the wiper motor that are closer together than the low speed brushes.
These brushes allow the motor to run at a faster speed but with less torque.
Front washer
Front washer operation will only activate when the following conditions are met:
lIgnition switch is in position I or II.
lFront washer switch operated.
Flicking the front washer switch energises the front washer pump motor for 0.4 second. Holding the front washer
switch for longer than 0.4 second allows the front washer pump motor to run as long as the switch is held.
There are two front washer configurations. If the vehicle is fitted with programme wash/ wipe, and the front washer
pump motor is active for more than 0.5 second, the front wipers operate at low speed. The wipers continue to operate
for 4 seconds after the washer switch is released. In some markets, the driver must activate the front wipers after a
front washer operation.
The front washer operation has a higher priority than the variable delay operation. This means that if intermittent wipe
is active when a front washer operation is initiated, the wash cycle executes and the intermittent wipe is re-instated
at the end of the wash operation.

WIPERS AND WASHERS
DESCRIPTION AND OPERATION 84-17
Front flick wipe
Flick wipe operation will only activate when the following conditions are met:
lIgnition switch is in position I or II.
lFront flick switch is operated.
Pressing the flick wipe switch operates the front wiper motor at high speed. The front wiper motor operates as long
as the flick switch is activated. Releasing the flick switch causes the front wiper motor to run through the park switch
circuitry. The park switch only permits low speed operation. Thus if the flick switch is pressed and immediately
released, the wipers operate at low speed.
Rear intermittent wipe variable delay
The rear intermittent wipe variable delay operation allows the driver to adjust the interval between wipes to suit local
conditions. Rear variable delay operation only activates if the following conditions are met:
lIgnition switch in position I or II.
lFront wash/ wipe switch on intermittent.
lRear wipe switch is operated.
The BCU determines the desired delay interval based on the setting of the variable delay switch. The rear wash/ wipe
delay is nominally twice as long as that of the front. This information passes from the IDM to the rear wiper relay and
activates the rear wiper motor.
If the delay duration is decreased during operation of the rear wiper, the wipers immediately operate once and the
delay cycle is reset.
If the delay duration is increased during operation of the rear wiper, the delay cycle is automatically increased by the
BCU.
Reverse wiping
Reverse wiping operates the rear wiper motor when reverse gear is selected. The transmission must be in reverse
for longer then 0.5 seconds before reversing wipe activates. Reversing wipe activates if the following conditions are
met:
lIgnition switch is in position II.
lReverse gear is selected.
lRear wiper or front wipers operating.
If the rear wiper is active in any mode when reverse gear is selected, the rear wiper activates for 4 second. After 4
seconds the rear wiper operates in a delay operation at the same delay interval set by the variable delay switch until
reverse gear is deselected.
If the front wipers are operating on either low or high speed when reverse gear is selected, the rear wiper activates
continuously until reverse gear is deselected.
In order to enable reversing wipe functions, the BCU utilises the reversing light switch located within the transmission
to determine when reverse gear has been selected.
If the front intermittent wipe is active when reverse gear is selected, the rear wiper completes 2 cycles before operating
at the same intermittent delay as the front wipers.

WIPERS AND WASHERS
84-18 DESCRIPTION AND OPERATION
Rear wipe
Rear wipe operation will only activate when the following conditions are met:
lIgnition switch is in position II.
lRear wipe switch is operated.
Operating the rear wiper switch provides an earth input to the BCU. The BCU tells the IDM to activate the rear wiper
relay, which provides battery voltage to the wiper motor through the normally closed contacts of the park switch.
Rear wash
Rear wash will only operate when the following conditions are met:
lIgnition switch is in position II.
lRear wash switch operated.
Operating the rear washer switch for longer than 0.4 second allows the rear washer pump motor and rear wipers to
run as long as the switch is held. The wipers run for 4 seconds after the rear washer switch is released. Flicking the
rear washer switch energises the rear washer pump motor for 0.4 second.
The rear washer operation has a higher priority than the intermittent wipe operation. If the intermittent wipe is active
when a rear washer operation is initiated, the wash cycle executes and the intermittent wipe is re-instated at the end
of the washer operation.
Wiper park switch
The park switch allows the wipers to come to rest in the park position when the wipe switch is turned off in mid-wipe.
The park switch consists of a positive and a negative contact. These two contacts are described as closed at park
and closed when operating. When the wipers first start, the park switch is in the closed at park position. A relay
controls battery voltage to the motor. Battery voltage passes through this relay contact to move the wiper motor from
the park position.
When the motor moves, the park switch moves to the closed when operating position. Battery voltage to this relay
contact is direct from fuse 19. Battery voltage passes through this contact to keep the wiper motor running. The wiper
motor operates for one complete revolution until the park switch moves to the closed at park position again.
Switching off the wipers removes battery voltage from the closed at park contact. When the wipers reach the closed
at park switch an earth is applied and the motor stops abruptly.
Headlamp power wash
Headlamp power wash activates when the following conditions are met:
lIgnition switch in position II.
lHeadlamps switched on.
lFront wash switch operated.
lBCU counter allows headlamp power wash.
Operating the front washer switch with the headlamps switched on energises the IDM, supplying a voltage to the
headlamp powerwash relay, which operates the headlamp powerwash pump and increments a counter within the
BCU. This counter prevents the headlamp powerwash pump from operating every time the front washer switch is
activated. Headlamp powerwash is only operational every third front wash cycle, providing the headlamps are on.
The counter resets when the ignition switch is turned off.
When the BCU permits headlamp power wash operation, the pump motor operates only for 0.5 second.

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
86-3-2 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 86-3-3
BCU outputs
The BCU processes the input signals it receives and uses the information to determine the control outputs that need
to be established for any given set of conditions. The BCU provides controlled outputs for the following systems:
lInterior courtesy lamps.
lFuel flap release actuator.
lAnti-theft status LED.
lEngine Control Module.
lDoor lock actuators.
lDirection indicators and hazard warning lamps.
lHeadlamps.
lAlarm sounder.
lVehicle horns.
lBattery backed sounder.
lStarter relay.
lPassive re-mobilisation exciter coil.
Simultaneous switching of outputs in different units is limited by the bus transfer time, but the skew is no longer than
100 ms for either the BCU or the IDM. When the processor is reset, all outputs are switched off until the inputs have
been read for the first time to check current condition.
BCU to harness connectors
1Connector C0661
2Connector C0662
3Connector C0663
4Connector C0660
5Connector C0664

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-5
C0661 connector pin details
Pin No. Description Input/Output
1 Serial bus to instrument pack and IDM Input/Output
2 Not used-
3 Battery backed up sounder code (AL) Output
4 Diagnostic bi-directional 'K'-line Input/Output
5 RF regulated power supply Output
6 RF receiver input Input
7 Brake switch activated Input
8 Reverse gear selected Input
9 Sunroof enable line Output
10 Robust immobilisation Output
11 Front washer pump Input
12 Heated front screen relay Output
13 Heated front screen active Output
14 Battery backed up sounder code (ST) Output
15 Heated rear screen active Output
16 'N' or 'R' or 'P' or brake selected Output
17 Not used-
18 Passive remobilisation exciter coil Output
19 RF battery supply from fuse 20 in passenger compartment fusebox Input
20 Security status LED Output
21 Front intermittent wiper Input
22 Driver's door key unlock Input