1999 LAND ROVER DISCOVERY headlamp

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.

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-29
Front fog lamps
Front fog lamp operation is monitored by the BCU, which allows only the front fog lamps to operate when the side
lamps or headlamps are on. When the side lamps, headlamps or ignition switch is turned off, the BCU also switches
off the fog lamps. When the side or headlamps are switched on again, the front fog lamps will remain off unless the
front fog lamp switch is pressed to resume operation. If the rear fog guard lamps are selected on, switching off the
front fog lamps will also switch off the rear fog guard lamps.
When the fog lamp switch is operated, an earth path is completed and the BCU allows the fog lights to be switched
on providing the logical preconditions have been satisfied. The BCU then supplies a voltage supply to the fog lamp
relay, to illuminate the fog lamps.
The front fog lamps option can be programmed in one of three states dependent on market/ customer requirements,
these are:
lOption 1– not fitted.
lOption 2 – main beam no effect.
lOption 3 – off with main beam.
The BCU checks the status of the following inputs to determine the logic action for providing an output to the front fog
lamp relay:
lIgnition state.
lMain beam state.
lSide lamps.
lDipped beam.
lFront fogs selected (press button, not latched).
If the ignition state is crank the state of the front fog relay is memorised and the relay is switched off. Pressing the
front fog switch during cranking will not be recognised. When the ignition state returns to Ignition after cranking, the
memorised front fog relay state is restored. If the ignition is turned off, the front fog relay is turned off.
For option 3 configuration, if the main beam is turned on the state of the front fog relay is memorised and the relay is
switched off. Pressing the front fog switch while main beam is on will not be recognised. When the Main beam state
returns to OFF, the memorised front fog relay state is restored.
In the event of a communications link failure while the front fog relay is on, the front fog relay will be switched off.
Rear fog lamps
The rear fog lamps operation is monitored by the BCU, which only allows the rear fog lamps to operate when the side
lamps or the headlamps are on. When the side lamps, headlamps or ignition is switched off, the rear fog lamps are
also switched off. When the side lamps or headlamps are switched on again, the rear fog lamps will not switch on
again unless reselected by operating the rear fog lamps switch. If front fog lamps are fitted, the rear fog lamps will be
switched off if the front fog lamps are switched off.
A supply voltage to the rear fog lamps relay is provided from a fuse in the passenger compartment fuse box, then
through two electronic switches in the IDM. With the lighting switch in the side lamp or headlamp position, an earth
path from the coil of the rear fog lamps relay completes the circuit through the two switches in the IDM to switch the
rear fog lamps on when the BCU receives a request signal from the rear fog lamps switch to turn the circuit on.
The BCU checks the status of the following inputs to determine the logic action for providing an output to the rear fog
lamp relay:
lIgnition state.
lMain beam state.
lDipped beam.
lFront fogs relay.
lRear fogs selected (press button, not latched).
If the ignition state is crank the state of the rear fog relay is memorised and the relay is switched off. Pressing the front
fog switch during cranking will not be recognised. When the ignition state returns to Ignition after cranking, the
memorised rear fog relay state is restored. If the ignition is turned off, the rear fog relay is turned off.
In the event of a communications link failure occurring while the rear fog relay is on, the rear fog relay will remain on
until the ignition is turned off or the dipped/ main beam is turned off.

BODY CONTROL UNIT
86-3-34 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.
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.

WINDOWS
DESCRIPTION AND OPERATION 86-5-5
Front window switches
The front window switches are non-latching rocker switches located in the center console. The front window switches
contain illumination bulbs that operate when the side lamps or headlamps are on.
The front window switches provide earth signals to the BCU. The BCU determines which direction to operate the front
window motors.
TestBook will monitor the real time status of the front window switches.

HARNESSES
REPAIRS 86-7-17
12.Disconnect multiplugs from headlamp and
sidelamp.
13.Disconnect multiplug from headlamp levelling
motor. 14.Release clip securing fog lamp multiplug.
15.Withdraw harness to engine compartment fuse
box.
16.Remove nut securing harness earth to body.
17.Release 4 clips and remove engine
compartment fusebox cover.

HARNESSES
86-7-20 REPAIRS
38.Disconnect multiplugs from headlamp and
sidelamp.
39.Disconnect headlamp level multiplug from
headlamp levelling motor.
40.Release earth header behind headlamp.
41.Disconnect multiplug from front of washer
reservoir.
42.Release clip securing fog lamp multiplug. 43.Disconnect 2 multiplugs from washer pumps.
44.Remove 2 clips securing washer pipes to
washer reservoir motors.
45.Remove washer reservoir pipes.
46.Release 2 bolts securing earth points to body.
47.Pull harness into engine bay.

HARNESSES
REPAIRS 86-7-27
94.Disconnect 3 multiplugs from LH rear door
harness.
95.Withdraw harness to interior.
96.Manoeuvre harness over steering column
support bracket.
97.With assistance remove main harness.
Refit
1.With assistance position main harness to body
and manoeuvre over steering column support
bracket.
2.Lay harness in position and secure to floor
clips and retainers.
3.Connect LH and RH rear door multiplugs.
4.Connect CD player multiplug.
5.Position centre console earth headers and
secure with nuts.
6.Fit rear carpet.

+ INTERIOR TRIM COMPONENTS,
REPAIRS, Carpet - rear.
7.Connect DCU multiplug.
8.Connect Lucar to handbrake switch.
9.Fit and tighten nuts securing harness to
transmission tunnel.
10.Secure harness to pedal box.
11.Position footwell earth header and secure with
nut.
12.Feed RH side of harness into engine bay.
13.Position carpet.
14.Connect wiper motor multiplug, position
mechanism and secure with nuts and bolts.
15.Connect ECM multiplug.
16.Position RH lower 'A' post earth header and
secure with nut, connect cruise control
multiplug.
17.Connect RH front door and RH side body
harness multiplugs. 18.Secure multiplugs to steering column support
bracket and connect brake and clutch pedal
multiplugs.
19.Connect multiplugs to column switch and
passive coil.
20.Position passenger compartment fusebox,
connect multiplugs, fit fusebox to fascia and
secure with nut.
21.Connect ignition switch multiplug to fuse box.
22.With assistance feed LH side of harness into
engine bay.
23.Connect multiplugs to front door harness and
body harness.
24.Position earth headers to LH lower 'A' post and
secure with nuts.
25.Connect multiplugs to ECU pack.
26.Position harness in engine bay.
27.Connect and secure heated front screen
multiplugs.
28.Fit plenum molding.

+ HEATING AND VENTILATION,
REPAIRS, Plenum Air Intake.
29.Connect multiplugs to ABS sensor and fuel
cut-off switch.
30.Using draw string feed harness through inner
wing, remove draw string, connect repeater
lamp multiplug and fit lamp.
31.Connect multiplugs to ABS modulator.
32.Feed harness through to front panel.
33.Position body earth leads and secure with
bolts.
34.Connect washer reservoir multiplugs and
pipes, secure pipes with clips.
35.Secure fog lamp multiplug.
36.Secure earth header behind headlamp.
37.Connect multiplugs to headlamp level motor,
headlamp and side lamp.
38.Fit indicator lamp

+ LIGHTING, REPAIRS, Lamp - front
repeater - up to 03MY.
39.Connect multiplug to LH horn.
40.Feed harness to ACE accelerometer, connect
multiplug and secure with cable ties.
41.Connect cruise control, ABS sensor and brake
fluid level switch multiplugs.
42.Connect engine harness multiplug and feed
harness along RH wing to fuse box.
43.Using draw string pull harness through inner
wing, remove draw string, connect repeater
lamp multiplug and fit lamp.
44.Connect chassis harness multiplugs.
45.Position engine bay fuse box and connect
multiplugs, fit fuse box and secure with screws.
46.Connect multiplugs to front of fuse box.
47.Position battery and starter cables and secure
with screws.
48.Fit fuse box cover.
49.Position earth lead and secure with nut.

HARNESSES
86-7-28 REPAIRS
50.Feed harness through to front panel.
51.Secure fog lamp multiplug.
52.Connect headlamp level motor, headlamp and
side lamp multiplugs.
53.Fit indicator lamp.

+ LIGHTING, REPAIRS, Lamp - front
repeater - up to 03MY.
54.Secure harness to RH front panel.
55.Connect cooling fan and horn multiplug.
56.Secure harness to lower support rail.
57.Connect receiver drier and air temperature
sensor multiplugs.
58.Fit front bumper.

+ EXTERIOR FITTINGS, REPAIRS,
Bumper assembly - front.
59.Fit battery tray.
60.Fit air filter assembly.

+ ENGINE MANAGEMENT SYSTEM -
V8, REPAIRS, Air cleaner assembly.
61.Position both lower 'A' post trims and secure
with studs.
62.Fit heater assembly.

+ HEATING AND VENTILATION,
REPAIRS, Heater assembly - models with
air conditioning.

+ HEATING AND VENTILATION,
REPAIRS, Heater assembly - models
without air conditioning.
Harness - main - DVD unit
$% 86.70.25
Remove
1.Remove battery cover and disconnect the
battery earth lead.
2.Remove CD switch box.

+ IN CAR ENTERTAINMENT,
REPAIRS, Switch box - CD/DVD player.
3.Remove DVD player unit.

+ IN CAR ENTERTAINMENT,
REPAIRS, DVD screen/player unit.
4.Release screw covers, remove 4 screws and
remove front and rear grab handles from
drivers side.