1999 LAND ROVER DISCOVERY window

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-9
IDM outputs
The IDM receives the following signals from the BCU using the serial datalink to provide power outputs:
Description Signal type System
Unlock all doors enable Digital Locking/ Unlocking/ Alarm
Lock passenger and rear doors enable Digital Locking/ Unlocking/ Alarm
Superlock all doors enable Digital Locking/ Unlocking/ Alarm
Lock driver's door Digital Locking/ Unlocking/ Alarm
Rear fog lamps enable Digital Exterior lighting
Daylight running lamps enable Digital Exterior lighting
LH direction indicators enable Digital Direction indicators/ Hazard warning/ Alarm
RH direction indicators enable Digital Direction indicators/ Hazard warning/ Alarm
Gear position indicator illumination Digital Illumination
Headlamp main beam indicator disable Digital Illumination
Front wiper enable Digital Wipers and washers
Rear wiper enable Digital Wipers and washers
Rear window enable Digital Power windows
Shift lever solenoid enable Digital Automatic gearbox
Transfer box solenoid enable/ Alarm sounder
relayDigital Gearbox
Heated rear window enable Digital Heated screens

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-11
Programmable options
The BCU can be programmed with a number of options to satisfy specific market requirements and customer
preferences. The options can be set using TestBook.
Function Option Details
Transmission Manual The vehicle is fitted with manual transmission.
Automatic The vehicle is fitted with automatic transmission.
Front fog lamps None The vehicle is not fitted with front fog lamps.
Main The front fog lamps will operate if the headlamps are on main beam.
No main The front fog lamps will not operate if the headlamps are on main
beam.
Interlocks None The vehicle is not fitted with key, shift or transfer box interlocks.
Shift The vehicle is fitted with key, shift and transfer box interlocks.
No transfer The vehicle is fitted with key and shift interlocks, but not a transfer box
interlock.
Daylight running lamps None The vehicle is not fitted with daylight running lamps.
No main The daylight running lamps are on if the headlamp main beams are off.
No heads The daylight running lights are on with headlamp main and dipped
beams off and the gearbox not in Park.
Programmed wash/ wipe Normal The front wipers operate if the front wash is operated.
No wipe The front wipers do not operate if the front wash is operated.
Key-in warning Disabled The ignition key in audible warning is disabled.
Enabled The ignition key in audible warning is generated if the ignition key is in
and the driver's door is open.
Electric front seats None The vehicle is not fitted with electric front seats.
Normal Electric seat adjustment is available for 45 seconds after the driver's
door opens or if the ignition is on.
Ignition II Electric seat adjustment is available if the ignition is on.
Electric front windows Driver cancel The front windows will be disabled 44 seconds after the driver's door
is opened.
All cancel The front windows will be disabled 44 seconds after any door is
opened.
No cancel The front windows will be disabled when the ignition is turned off.
Heated front screen Fitted The vehicle is fitted with heated front screens.
None The vehicle is not fitted with heated front screens.
Rear windows and sunroof Driver cancel The rear windows and sunroof will be disabled 44 seconds after the
driver's door is opened.
All cancel The rear windows and sunroof will be disabled 44 seconds after any
door is opened.
No cancel The rear windows and sunroof will be disabled when the ignition
switch is turned off.
Gear position indicator
illuminationAlways The automatic gearbox selector illumination is on when the ignition is
on.
Sidelights The automatic gearbox selector illumination is on when the ignition is
on and the sidelights are off.
Hill descent control None The vehicle is not fitted with hill descent control.
Fitted The vehicle is fitted with hill descent control.
Courtesy headlamps Disabled The vehicle is not fitted with courtesy headlamps.
Enabled The vehicle is fitted with courtesy headlamps.
Odometer error warning Disabled The odometer will not flash if there is an odometer error.
Enabled The odometer will flash if there is an odometer error.

BODY CONTROL UNIT
86-3-14 DESCRIPTION AND OPERATION
Central Door Locking (CDL)
The BCU carries out the logic control operation for CDL. A CDL switch is mounted on the fascia panel and has two
inputs to the BCU, one for lock and one for unlock.
Door locking and unlocking can be performed using the remote transmitter in the keys and the receiver unit located
above the vehicle's headlining, behind the rear sunroof aperture. The receiver detects the signals sent from the
remote transmitter and sends a decoded signal to the BCU for processing.
Four methods of door locking are available:
lRemote handset locking.
lVehicle key locking.
lCDL switch locking.
lSpeed related locking.
Two security levels of door locking are available, CDL and Superlocking. The anti-theft alarm system works in
conjunction with the CDL system.
Electric windows and sunroof
The BCU controls the logical operations and the timing periods for the electric front windows. The rear windows are
hard-wired and the two electric sunroofs are controlled by a dedicated ECU which is enabled by the BCU.
The front windows are electrically operated using two rocker switches located in the centre console. Electric motors
are located in each of the front doors.
The rear windows are enabled by the IDM controlling the operation of the rear window relay located in the passenger
compartment fuse box.
Wipers and washers
The wiper and washer functions are controlled by the BCU and the IDM.
The front wipers and washers are operated from the switch stalk located on the right hand side of the steering column
and only operate when the ignition switch is in position I or II. The front wipers are operated by a motor located below
the windscreen plenum.

+ WIPERS AND WASHERS, DESCRIPTION AND OPERATION, Description.
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.

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-17
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.
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 on vehicles up to 2003 model year or in the instrument pack binacle on vehicles from
2003 model year. The switch receives a voltage supply from the passenger compartment fuse box.

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-19
Operation
For IDM inputs which are also inputs for BCU functions, the delay before the BCU recognises the change in input
status is less than 250 ms. The BCU uses a debounce algorithm to ignore changes in input having a duration less
than 100 ms with the exception of automatic gearbox W, X, Y, Z inputs, which have a debounce period of 33 ms.
Transit mode
To prevent excessive battery drain during transit to overseas markets, the vehicle is placed in a transit mode.
To exit the transit mode, simultaneously hold down the heated rear window switch and the rear fog lamp switch, turn
the ignition switch from 0 to II and, after a minimum of 2 seconds, release the switches.
Transit mode can be entered using TestBook. When TestBook communicates with the BCU for diagnostics related to
BCU operation, it first checks that the vehicle is not in transit mode.
Anti-theft system
The BCU uses the driver's door key lock and unlock switches to activate and deactivate the security system. The
driver's door lock is also used for entering the EKA.

+ ALARM SYSTEM AND HORN, DESCRIPTION AND OPERATION, Description.
Immobilisation
For immobilisation, the BCU disables the starter motor relay. When the engine is cranking, the ECM looks for a coded
signal from the BCU. If the signal is not received within one second of cranking, the fuel supply to the engine is
stopped and the injectors are disabled. This also prevents unburnt fuel from entering the catalyst.
If the BCU is disconnected, the engine starter motor will remain isolated by the starter motor relay and the ECM will
remain immobilised. The main wiring for the system is contained within the main harness which is relatively
inaccessible, so preventing intruders from disabling the system by cutting the wires for the immobilisation system.
Once the immobiliser has been activated, destruction of the trigger device or the wiring to it will not disarm the system.
The RF transmitter communicates to the BCU via the RF receiver using a 70 bit code. Pressing the unlock button on
the transmitter will re-mobilise the vehicle. The RF transponder is integrated into the metal key assembly, inserting
the key into the ignition switch will induce a signal in the exciter coil to re-mobilise the vehicle.
Anti-theft alarm
The alarm system provides a warning of unauthorised access to the vehicle and includes perimetric and volumetric
monitoring under the control of the BCU.
The perimetric protection system detects opening of all doors, tail door and bonnet and will also detect the operation
of the ignition key switch. The following conditions must be satisfied before the BCU will operate all of the functions
of perimetric protection:
lAll doors and hinged panels are in the closed position.
lIgnition key out of the ignition switch.
lInertia switch is not tripped.
If all conditions are not satisfied the BCU will enter a mislock condition.
The volumetric sensor uses two ultrasonic sensors mounted in the headlining to detect movement within the vehicle.
The alarm will trigger when the sensor signals the BCU for 200 ms or greater. Within a single setting period the alarm
system will allow a maximum of 10 triggers as a result of any combination of sensor inputs. It is possible to lock the
vehicle without enabling the volumetric alarm by using the key. The same conditions needed to satisfy enabling of the
perimetric protection system is also needed to enable volumetric protection.
When the alarm system is set the BCU checks the status of all the inputs from the door and bonnet switches to ensure
the integrity of the vehicle before setting the alarm system into operational mode. In some markets, when the alarm
is set the BCU sends a signal to the IDM which will cause the direction indicators to flash three times for a duration of
3 seconds.
If the sensors are triggered the BCU will activate an alarm sounder to provide an audible warning of a theft attempt.
The activation period of the alarm sounder is 25 to 30 seconds. The duty cycle of the alarm sounder is 50:50 ± 10%.

BODY CONTROL UNIT
86-3-22 DESCRIPTION AND OPERATION
Electric windows and sunroof
Three modes of operation are available:
lDriver cancel – the front windows, rear windows and sunroof will be disabled 44 seconds after the driver's door
is opened.
lAll cancel – The front windows, rear windows and sunroof will be disabled 44 seconds after any door is opened.
lNo cancel – the front windows, rear windows and sunroof will be disabled when the ignition is turned off.
The BCU will allow window and sunroof operation when the ignition key is in position II. The BCU provides a voltage
to the window control switches. When the switches are pressed, they provide a path to earth to complete the circuit
and initiate window operation. Window and sunroof operation is suspended when the ignition switch is in the crank
position.
For front window operation, the BCU checks the status of the following inputs:
lIgnition state.
lDriver's door open.
lPassenger or rear door open.
lFront right window down.
lFront right window up.
lFront left window down.
lFront left window up.
lRight window stall detect.
lLeft window stall detect.
The front window motors are directly connected to the BCU by two wires. Each wire can be used as a feed or return,
dependent on the required direction for motor operation (open or close). The BCU provides the following outputs:
lRight window up.
lRight window down.
lLeft window up.
lLeft window down.
The electric front windows are enabled when the ignition switch is in position II and is disabled if the ignition switch is
moved to the crank position.
The BCU checks the status of the following inputs to determine when to provide the rear window enable and sunroof
enable output signals:
lIgnition state.
lDriver's door open.
lPassenger or rear door open.
The rear window enable and sunroof enable lines are on when the ignition switch is in position II, and are switched
off if the ignition switch is moved to the crank position.
The BCU monitors the circuit current draw when the windows are operating to detect the occurrence of a stall
condition. If the BCU determines that the window has stalled, it will cut the power supply to stop the operation of the
window motor. The BCU only starts to check for a stall condition after the window has been operating for 500 ms. This
delay period enables the initial current surge to pass and eliminates false detections of window stall. A stall condition
is activated when a nominal current value is exceeded for a period greater than 300 ms.
If the BCU detects that it has been operating the same window motor in one direction for more than 10 ± 0.2 seconds,
without the BCU detecting a stall condition or the control switch being released, it will automatically stop operation of
the window motor (timed out). Window operation can resume when the window switch is released and pressed again.
If the window was operating in one touch mode, the window operation will resume on the next press of the window
switch.
One touch mode automatically lowers the window to its fully open position, without the need for the window switch to
be kept pressed for the duration of the window travel. One touch mode is initialised if the window switch is pressed
for a period of less than 0.4 ± 0.2 second. One touch mode continues to lower the window until the BCU detects:
lA stall condition exists (window has reached bottom of travel).
lWindow switch is repressed in either direction for more than 0.4 ± 0.2 second.
lThe BCU has operated the motor for a period greater than 10 ± 0.2 seconds.

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-23
A timeout function is included which allows the windows and sunroofs to be operated for a period of 44 ± 1 seconds
after the ignition key has been removed from the ignition switch. The timeout function will be cancelled if the BCU
detects the following conditions:
lThe driver's door has been closed after the ignition has been switched off.
lAny door open after the ignition is switched off.
The preconditions are programmed into the BCU dependent on market specification.
The BCU does not directly control rear window operation, but it can request the IDM to remove the power feed to the
rear windows. The IDM enables power supply to be provided to the rear lift relay in the passenger fuse box. When the
relay coil is energised the relay contacts close and power is applied to the rear window motor. If the window lift
isolation switch located in the centre console is latched out, the earth path from the LH and RH rear door window
switches is broken and operation of the rear window motors through the use of the rear window switches is prevented.
Rear window operation using the console switches is not affected by the isolation switch.
In the event of a communications link failure occurring while rear window enable is on, the relay remains on until the
ignition switch is turned to the off position.
Heated screens
The heated screen time-outs and logical operations are controlled by the BCU.
Heated front screen
The BCU provides an output to the heated front screen relay and a 'heated front screen active signal' for the heated
front screen warning lamp. The BCU uses the status of the following inputs to determine the appropriate logical
operations for this feature:
lIgnition state.
lEngine running (link from instrument pack).
lHeated front screen selected (non-latched button pressed).
If the ignition switch is not in position II, or the engine running signal is OFF, the heated front screen will not be active.
The heated front screen operation period and voltage supply is controlled by the BCU. The BCU receives a voltage
supply feed from the engine compartment fuse box and an ignition switched supply through a fuse in the passenger
compartment fuse box. When the heated front screen switch is operated, it completes a path to earth, signalling a
request for heated screen operation to the BCU. The BCU then supplies a feed to the heated front screen switch to
light the switch indicator, and earths the supply from the coil of the heated screen relay to turn the heated front screen
on. The BCU maintains a supply for a predetermined time (5 minutes), then opens the earth path after the time out
period to turn the heated screen off. During the timeout period, if the heated front screen switch is pressed a second
time, the circuit is also interrupted to turn off the supply to the heated front screen.
On vehicles fitted with air conditioning, the heated front screen is also operated by the ATC ECU when DEF (defrost)
is selected. In this case the ATC ECU provides the trigger signal to the BCU to turn the heated front screen circuit on
or, if it is already on, to re-start the time out period.

+ AIR CONDITIONING, DESCRIPTION AND OPERATION, Description.
In the event of a communications link failure occurring while the heated front screen relay is on, the relay and lamp
will remain on until the ignition switch is turned off or the time-out period elapses or the heated front screen switch is
pressed.
Heated rear window
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 BCU provides a 'heated rear window enable output' and a 'heated rear window active warning lamp signal' based
on the logic status of the following inputs:
lIgnition state.
lEngine running (link from instrument pack).
lHeated rear window selected (non-latched button pressed).
If the ignition switch is not in position II, or the engine running signal is OFF, the heated rear window will not be active.

BODY CONTROL UNIT
86-3-24 DESCRIPTION AND OPERATION
The heated rear window operation period and voltage supply is controlled by the BCU. The BCU receives a voltage
supply feed from the engine compartment fuse box and an ignition switched supply through a fuse in the passenger
compartment fuse box. When the heated rear window switch is operated, it completes a path to earth, signalling a
request for heated rear window operation to the BCU. The BCU then supplies a feed to the heated rear window switch
to light the switch indicator, and earths the supply from the coil of the heated rear window relay via the IDM to turn the
heated rear window elements on. The BCU maintains a supply for a predetermined time (15 minutes), then opens the
earth path after the time-out period to turn the heated rear window operation off. If the heated rear window switch is
pressed a second time, the circuit is also interrupted to turn off the supply to the heated front screen.
On vehicles fitted with air conditioning, the heated rear window is also operated by the ATC ECU when DEF (defrost)
is selected. In this case the ATC ECU provides the trigger signal to the BCU to turn the heated rear window circuit on
or, if it is already on, to re-start the time out period.

+ AIR CONDITIONING, DESCRIPTION AND OPERATION, Description.
In the event of a communications link failure occurring while the heated rear window enable is on, the relay and lamp
will be de-activated.
Wipers and washers
Front and rear wash/ wipe operations are controlled by the BCU via the IDM.
Front wipers and washers
When front intermittent wipe is selected using the wiper switch on the column stalk, the BCU signals the IDM to
operate the wiper motor. The IDM then supplies a voltage to the normal speed winding of the wiper motor for a period
of no longer than 500 ms. The timed feed ensures the wiper motor operates, but does not complete more than a single
wipe of the screen. The BCU checks the position of the delay switch to determine the delay period which should be
utilised for the intermittent wipe operation. The delay period of the front intermittent wipe is maintained until the wiper
switch is moved to the off, normal or fast speed position, or the delay period is changed.
When front intermittent wipe is selected, a delay period of 500 ms will be incurred before the wipers operate. This
delay prevents the occurrence of a wipe action when the wiper switch is changed to the off position from the normal
or fast modes of operation.
To enable the front intermittent wipe facility, the BCU checks the state of the following inputs:
lIgnition state.
lFront intermittent wiper switch.
lFront intermittent wiper rate.
If the ignition switch is in the off or crank position, the front wipers are not active and the front wiper enable output is
switched off.
If the option to initiate a wipe action in addition to a front screen wash action has been configured in the BCU, the
wipers will operate 400 ms after the washer pump becomes active. If the washer switch is released within 400 ms,
the wipers will not be activated. If a washer switch is pressed for longer than 400 ms, the BCU will operate the wipers
after an initial delay of 400 ms, and will continue to operate for as long as the washer switch is depressed plus an
additional 4 seconds.
The front wash/ wipe programme can be configured to operate in one of two ways:
lOption 1 – normal.
lOption 2 – no wipe.
The BCU checks for the following inputs:
lIgnition state.
lFront washer pump switch.
The BCU can provide the following wash / wipe outputs depending on the logic states prevailing:
lFront wiper enable.
lFront wash/ wipe in progress flag.
In the event of a communications link failure occurring while the front wash/ wipe programme is in operation, the front
wiper enable output is switched off.