oil change LAND ROVER DISCOVERY 1999 Owner's Manual

BODY CONTROL UNIT
86-3-20 DESCRIPTION AND OPERATION
In some markets, when the alarm is triggered the BCU also activates the direction indicators, in phase with the audible
warning, to provide an optical warning of a theft attempt. The activation period of the optical alarm is 25 to 30 seconds.
The duty cycle of the optical warning is 50:50 ± 10%.
The alarm system relies upon the vehicle battery for power. However, the BCU remembers the status of the security
system if it loses battery supply. If the security system was in a set condition when battery supply was lost the BCU
will trigger the alarm and initiate a visual warning by flashing the hazard lamps when the battery voltage is restored.
On vehicles with a BBUS fitted, the BBUS will sound if the battery is disconnected while the alarm system is set.
Door switches
The BCU uses the door latch switches to indicate if a door is open or closed. The BCU provides power to all door latch
switches; the switches are in the 'normally open' condition when the doors are shut. When a door is opened, the door
switch contacts are closed and the circuit is earthed, signalling a change in state to the BCU. All doors except the
driver's doors are connected in parallel, so the BCU will recognise a passenger door has been opened but will not be
able to distinguish which one. The driver's door has a dedicated signal line which enables the BCU to detect if the
driver's door has been opened or closed.
Door lock actuators
The CDL system has the facility to enable superlocking. All door lock actuators are controlled by the BCU via the IDM.
The driver's door is controlled separately from all other doors, enabling functions like single point entry and key
access.
Driver's door key lock and unlock switches
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 code.
Two separate switches are incorporated into the key lock assembly of the driver's door. The switches are normally
open and the BCU provides a separate power supply to each. The BCU is signalled when a circuit is earthed enabling
it to determine the direction in which the lock has been turned.
Bonnet switch
The bonnet switch is powered from the BCU and is used as a logical input for operation of the security system. The
switch is normally open with the bonnet closed, when the bonnet is opened the switch contacts close to complete a
circuit to earth and signal the change in state to the BCU.
Key-in sensor
When the ignition key is inserted into the lock barrel the key-in sensor contacts close and supply a signal to the BCU.
The BCU monitors the ignition switch for a change in state and triggers the alarm if it receives an ignition signal before
it receives an alarm disarm signal.
Another feed to the ignition switch is provided by the BCU to provide switch illumination.
A key-in warning can be enabled or disabled. When the key-in warning is enabled, an audible warning is generated
if the ignition key is in and the driver's door is opened.
Passive coil
The passive coil is located around the ignition key barrel. When the BCU detects that the ignition key has been turned
to the crank position, the vehicle's immobilisation system is activated and a signal is sent to the passive coil at a
frequency of 125 kHz. The magnetic field generated in the coil is induced in the remote transmitter to trigger a re-
mobilisation signal.
BBUS/ alarm sounder/ vehicle horn
The BBUS is an audible warning device which operates under the control of the BCU if the anti-theft system is
activated or the vehicle battery is disconnected. The unit contains its own internal battery power source which is
charged via a feed from the passenger compartment fuse box. The BBUS will not sound if the battery is disconnected
while the security system has not been set.
Some markets utilise an alarm sounder which operates independently or in conjunction with the vehicle horn if the
anti-theft system is triggered.

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.

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-25
Rear wipers and washers
The rear wiper is initially operated for a period of 4 seconds when the rear wiper switch is pressed, to complete two
full cycles. After this, the rear wiper will operate every other time the front wiper completes a wipe operation. During
the wipe operation, the front and rear wipers are synchronised, and changes to the delay period during intermittent
wipe will change the delay period for both front and rear wipers.
Operation of the rear washer switch causes the washer motor to operate for as long as the switch is operated. The
wiper also operates while the switch is depressed and for a further 4 seconds after the switch is released.
The BCU checks for the following inputs to determine when to provide the rear wiper enable signal:
lIgnition state.
lRear wiper switch.
lFront intermittent wiper rate.
lFront intermittent wiper switch.
If the ignition switch is in the off or crank position, the rear wipers are not active and the rear wiper enable output is
switched off.
In the event of a communications link failure occurring while the rear intermittent wipe programme is in operation, the
rear wiper enable output is switched off.
Reverse gear wipe
The BCU changes the operation of the rear wiper when the front wiper is active and reverse gear is selected. The rear
wiper operation rate used when the preconditions have been satisfied depend on the prevailing front wiper operating
mode and the position of the rear wiper switch. If the rear wiper is on or the front wiper is operating at an intermittent
rate when reverse gear is selected, the BCU will operate the rear wiper continuously for 4 seconds via the IDM. After
the initial period, the rear wiper will operate at the same rate as the front wiper.
The BCU checks for the following inputs to determine when to provide the rear wiper enable signal if the vehicle is in
reverse gear:
lIgnition state.
lRear wiper switch.
lFront intermittent wiper rate.
lReverse gear selected.
lFront intermittent wiper switch.
lFront wiper switch state.
lFront wash/ wipe in progress flag.
In the event of a communications link failure occurring while the reversing wipe is in operation, the rear wiper enable
output is switched off.
Headlamp wash
The headlamp wash will only operate when the headlamps are on, and then only every third time the front windscreen
wash button is pressed. When the BCU operates the headlamp washers, it activates the washer pump relay for a
period of 500 ms. The BCU supplies an earth path for the coil of the power wash relay located in the engine
compartment fuse box when the washer function is selected.
The BCU checks for the following inputs to determine when to provide power to the headlamp power wash relay:
lIgnition state.
lFront washer pump switch.
lDipped beam.
lMain beam state.
If the ignition switch is in the off position, the headlamp power wash relay is also held off. if the ignition state is crank,
the headlamp power wash relay is switched off and the headlamp power wash counter is reset to 0.
In the event of a communications link failure occurring while the headlamp power wash relay in on , the relay remains
on until the 500 ms timer has completed, then the relay is switched off.

BODY CONTROL UNIT
86-3-28 DESCRIPTION AND OPERATION
Courtesy headlamps
This feature activates the headlamps for 30 seconds when the lock button on the remote transmitter is held down for
longer than 1 second. The headlamps will extinguish if the BCU receives either a lock or an unlock signal from the
remote transmitter.
The BCU checks the status of the following inputs to determine the correct qualifying conditions for requesting
courtesy headlamps:
lIgnition state.
lRemote locking request.
lRemote unlocking request.
lLazy locking request.
If the ignition is off and a lazy locking request is received, the courtesy headlamps are switched on and an internal
timer is turned on in the BCU which operates for 30 seconds. If the 30 second timer expires or a request for remote
locking or remote unlocking is received, the courtesy headlamps will be turned off.
When main beam is selected, the IDM also provides a signal to the instrument pack to switch on the main beam
warning lamp. An additional signal 'main beam indicator disable' is used to prevent the daylight running lamps
illuminating the main beam indicator when the main beam is in the daylight running lamp state and the main beam
indicator disable signal is on.
Lights on alarm
The lights on alarm in the instrument pack operates when the driver's door is open and the side lamps or headlamps
are on. The system uses inputs from the driver's door switch and the lighting switch to determine the logical conditions
that need to occur for switching on the alarm. The BCU carries out the logic operation and communicates with the
instrument pack using the serial data bus; the instrument pack will be requested to sound the alarm if the logic inputs
indicate that the driver's door is open with the lights still on.
Supply voltage is provided through the lighting switch to the IDM which acts as the signal line to indicate that the lights
are on for the logic circuits in the IDM and BCU. When the driver's door is opened, a second feed is supplied to the
BCU through the driver's door switch to indicate the condition. In this logic condition (lights on and driver's door open)
the BCU signals the instrument pack to operate the audible warning. If the lights are switched off or the driver's door
is closed the logic condition will be changed and the audible warning will be switched off.
Daylight running lamps
The BCU operates the daylight running lamps (where fitted) via the IDM. The daylight running lamps option can be
programmed in one of three states dependent on market/ customer requirements, these are:
lOption 1– no daylight running lamps.
lOption 2 – on with main beam off.
lOption 3 – on with main and dipped beam off and gearbox not in Park.
The BCU will ensure the logical conditions are satisfied for the lamps to operate under the set conditions. The BCU
checks the status of the following inputs to determine the logic action for providing an output to the daylight running
lamp relay:
lMain beam state.
lEngine running (link from instrument pack).
lDipped beam.
lGearbox state.
A voltage supply is fed to the coil of the daylight running lamp relay and the IDM. When the preconditions are satisfied
for daylight running lamp operation, the BCU sends a signal for the IDM to complete the circuit to earth to switch on
the daylight running lamps. The logical inputs are checked to ensure that the engine is running before switching the
relay to turn on the daylight running lamps. The engine running signal has to be present for at least 2 seconds before
the daylight running lamp relay can be switched on.
Fog lamps
The BCU operates the rear fog lamps and the front fog lamps (where fitted) via the IDM. The BCU front fog lamp
operation can be programmed to operate under one of three set conditions. The BCU will ensure the logical conditions
are satisfied for the lamps to operate under the set conditions.