Land Rover Discovery 99my To 03my Electrical Library 3rd Edition Rover Manual

							DESCRIPTION AND OPERATION
4.120DISCOVERY SERIES II
Front Fog Lamps Operation
When the front fog lamp switch is operated, an earth path is completed from the BCU pin 
C0660-7 to the switch on a KB wire. The earth path continues through the switch contacts 
and is connected to earth header C0017 LHD/C0018 RHD on a B wire, via header C0760.
The completion of the earth path signals the BCU to provide an earth path from the coil of 
the front fog lamp relay in the engine compartment fusebox to the BCU pin C0663-4 on a 
UY wire.
The energised coil closes the contacts in the front fog lamp relay. This allows the feed from 
fuse 3 to pass through the relay contacts and from the engine compartment fusebox to 
header C0293 on a UP wire.
From the header C0293, the feed is connected on a UP wire to the RH front fog lamp, which 
connected to earth header C0018 by a B wire.
A second feed from the header C0293 is connected on a UP wire to the LH front fog lamp, 
which is connected to earth point C0564 by a B wire.
Switch indicator lamp operation
A third feed from header C0293 is connected to the front fog lamp switch on a UP wire. The 
feed passes through the front fog lamp switch indicator lamp which illuminates. The indicator 
lamp is earthed from the front fog lamp switch to earth header C0017 LHD/C0018 RHD, via 
header C0760 on a B wire. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.121
REAR FOG GUARD LAMPS
DESCRIPTION
General
The rear fog guard lamps are controlled by a non-latching switch located on the left side of 
the instrument pack. The lamps are located in the rear bumper, adjacent to the indicator 
lamps. Rear fog guard lamp operation is monitored by the Body Control Unit (BCU) which 
only allows the lamps to operate when the side lamps or headlamps are on and the front fog 
lamps are switched on.
When the side lamps, headlamps or ignition is turned off, the rear fog guard lamps are 
extinguished. When the side or headlamps are switched on again, the rear fog guard lamps 
will not operate until reselected using the switch. If the front fog lamps are switched off, the 
rear fog guard lamps will also switch off.
The rear fog guard lamp switch is illuminated when the side lights are switched on. Each rear 
fog guard lamp bulb is rated at 21 Watts.
OPERATION
Rear Fog Guard Lamps Supply
Circuit supply
A feed from the battery positive terminal is connected by an R wire to the engine 
compartment fusebox, where it passes through fusible links 8, 10 and 13 and fuse 13.
A feed from fusible link 13 is connected by an NG wire to the lighting switch.
A feed from fusible link 10 is connected by an U wire to the passenger compartment fusebox. 
The feed passes through fuse 4 in the passenger compartment fusebox and connects to the 
contacts of the rear fog guard lamp relay.
A feed from fusible link 8 is connected on an NW wire to the passenger compartment 
fusebox and from the fusebox to the ignition switch on an N wire.
A feed from fuse 13 is connected by a PN wire to the passenger compartment fusebox. The 
feed connects to the coil of the rear fog guard lamp relay. The relay coil is connected inside 
the passenger compartment fusebox to two electronic switches in the Intelligent Driver 
Module (IDM) which is integral with the fusebox. 
						

							DESCRIPTION AND OPERATION
4.122DISCOVERY SERIES II
Ignition switch supply
With the ignition switch in position II, the feed from fusible link 8 flows through the ignition 
switch to the passenger compartment fusebox on a Y wire. The feed continues through fuse 
29 in the passenger compartment fusebox and is connected to one of the two electronic 
switch in the IDM.
In this condition, one of two switches in the IDM closes. The earth path from the IDM is 
connected from the passenger compartment fusebox to earth header C0551 on a B wire.
Lighting Switch Operation
When the lighting switch is moved to the side lamp or headlamp position, the feed from 
fusible link 13 passes through the switch contacts and is connected from the lighting switch 
to the passenger compartment fusebox on an R wire. The feed is connected to the IDM, 
causing the second of the two electronic switches to close.
Body Control Unit
With the lighting switch in the side lamp or headlamp position an earth path from the coil of 
the rear fog guard lamp relay is completed through the two electronic switches in the IDM. 
The earth is connected by an SK wire to BCU pin C0661-1, via header C0293 LHD/C0292 
RHD. This connection is the serial data bus between the BCU and the IDM.
The BCU is connected to earth header C0551 from pin C0660-11 on a B wire and from pin 
C0664-5 on a B wire to earth header C0018 LHD/C0017 RHD.
Rear Fog Guard Lamp Switch Operation
When the rear fog guard lamp switch is operated, an earth path is completed from the BCU 
pin 662-8 to the switch on a UP wire. The earth path continues through the switch contacts 
and is connected to earth header C0017 LHD/C0018 RHD on a B wire, via header C0760.
The completion of the earth path signals the BCU to provide an earth path from the coil of 
the rear fog guard lamp relay, through the two IDM electronic switches to the BCU on the 
SK wire.
The energised coil closes the contacts of the rear fog guard lamp relay. This allows the feed 
from fuse 4 in the passenger compartment fusebox to flow through the relay contacts.
From the fusebox the feed is connected on a RY wire, to connector interface C0020-1/
C0905-1. From this interface the feed continues on a R wire to connector interface C0905-
2/C0020-2. From this interface the feed continues on a RY wire to the trailer pick-up socket. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.123
From the connector interface C0905-2/C0020-2, the feed is connected on a Y wire to 
connector interface C0905-3/C0020-3. From this interface the feed is connected on an RY 
wire to header C0295.
A feed from header C0295 is connected on an RY wire to the RH rear fog guard lamp which 
in turn is connected to earth header C0706 on a B wire.
A second feed from header C0295 is connected on a RY wire to the LH rear fog guard lamp 
which in turn is connected to earth header C0707 on a B wire.
Switch Indicator Lamp Operation
A second feed from the rear fog guard relay is connected from the passenger compartment 
fusebox to the rear fog guard lamp switch on an RY wire. The feed passes through the rear 
fog guard lamp switch indicator lamp which illuminates. The indicator lamp is earthed from 
the rear fog guard lamp switch to earth header C0017 LHD/C0018 RHD, via header C0760 
on a B wire. 
						

							DESCRIPTION AND OPERATION
4.124DISCOVERY SERIES II
INDICATORS AND HAZARDS
DESCRIPTION
General
The direction indicator lamps are operated from a three position direction indicator switch 
located on the left hand side of the steering column and only operate with the ignition switch 
in position II. Left and right indicator lights in the instrument pack flash accordingly to show 
correct flasher operation. If a failure of an indicator bulb occurs, the appropriate flasher 
symbol on the instrument pack will flash quickly.
The hazard warning lamps are operated from a latching pushbutton switch located in the 
group of six switches on the fascia. When the switch is pushed, both left and right indicator 
lights in the instrument pack flash to show hazard warning lamps are operating and all 
hazard warning lamps flash simultaneously. The hazard warning flashers operate 
independently of the ignition switch position.
If a trailer is fitted and connected to the trailer pick-up socket, a trailer symbol in the 
instrument pack also flashes to show correct operation of the trailer direction indicator/
hazard warning lamps.
Two direction indicator/hazard warning lamps are located outboard of the headlamps. Two 
side repeater lamps are located on the left and right hand front wings, forward of the A posts. 
Two rear direction indicator/hazard warning lamps are located in the rear bumper. All 
direction indicator/hazard warning lamp bulbs are rated at 5 Watts.
The direction indicators and hazard warning lamp operation is controlled by the Body 
Control Unit (BCU), Intelligent Driver Module (IDM) and two electronic relays in the 
passenger compartment fusebox. The IDM and the relays are are an integral part of the 
passenger compartment fusebox and cannot be serviced individually.
The direction indicator circuit uses the serial data bus between the BCU, IDM and the 
instrument pack for flasher and hazard request and operation. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.125
OPERATION
Direction Indicators and Hazard Warning Lamps Supply
Circuit supply
A feed from the battery positive terminal is connected by an R wire to the engine 
compartment fusebox, where it passes through fusible link 8 and fuse 14.
A feed from fuse 14 is connected to the passenger compartment fusebox on a PN wire 
where it is connected to the contacts and coils of the RH and LH indicator relays in the 
fusebox.
A feed from fusible link 8 is connected on an NW wire to the passenger compartment 
fusebox and from the fusebox to the ignition switch on an N wire.
Ignition switch supply
With the ignition switch in position II, the feed from fusible link 8 flows through the ignition 
switch to the passenger compartment fusebox on a Y wire. The feed continues through fuse 
29 in the passenger compartment fusebox and is connected on a GU wire to the BCU pin 
C0660-1.
Direction Indicator Lamps Operation
The BCU supplies a reference voltage from pin C0663-2 on a GR wire for the LH flasher and 
from pin C0660-6 on a GW wire for the RH flasher. When the flasher switch is moved to the 
LH or RH hand flasher position an earth path is completed from the switch on a B wire, via 
header C0286 LHD/C0291 RHD to earth header C0018 LHD/C0017 RHD. The completion 
of the earth, signals the BCU that a request for LH or RH flasher operation has been made.
The BCU then sends a signal on an SK wire from pin C0661-1, via header C0293 LHD/
C0292 RHD, to the IDM in the passenger compartment fusebox. The SK wire is the serial 
data bus between the BCU, IDM and the instrument pack.
The signal is received by the IDM and interpreted as a request for LH or RH flasher 
operation. The IDM grants an earth path for the coil of the LH or RH direction indicator relay. 
The coil is energised by the feed from fuse 14 in the engine compartment fusebox, closing 
the relay contacts.
With the contacts closed, the feed from fuse 14 also passes through the relay and is 
connected, via a resistor, from the passenger compartment fusebox to the applicable 
direction indicator. The IDM controls the flasher operation by momentarily removing and 
restoring the earth for the relay coil, which opens and closes the contacts causing the 
indicator bulbs to flash on and off. 
						

							DESCRIPTION AND OPERATION
4.126DISCOVERY SERIES II
The resistor is used by the IDM to monitor the current drawn through the resistor by the 
direction indicator bulbs. If an indicator bulb fails, the IDM detects the drop in current draw 
across the resistor and operates the flasher relay at a faster speed. The faster flash is also 
transmitted to the instrument pack to inform the driver of the bulb failure.
The IDM operates the direction indicator lamps in the instrument pack on the serial data bus 
on the SK wire from the passenger compartment fusebox, via header C0293 LHD/C0292 
RHD, to the instrument pack.
The direction indicators are connected from the passenger compartment fusebox as follows:
LH front, rear and side direction indicator/hazard warning lamps
The feed from the LH direction indicator relay is connected on a GR wire from the passenger 
compartment fusebox to header C0289.
LH front
The feed is connected from header C0289 on a GR wire to the LH front direction indicator/
hazard warning lamp. The lamp is connected on a B wire, via header C1001 LHD/C0288 
RHD, to earth eyelet connector C0564-1 LHD or earth header C0017 RHD.
LH rear
The feed is connected from header C0289, via header C0295, on a GR wire to the LH rear 
direction indicator/hazard warning lamp. The lamp is connected on a B wire to earth header 
C0707.
LH Side repeater
The feed is connected from header C0289 on a GR wire to the LH front side repeater lamp. 
The lamp is connected on a B wire, via header C0288, to earth header C0017.
Trailer connection
The feed for the trailer connection is taken from header C0289, via header C0295, on a GR 
wire to the trailer pick-up. The trailer pick-up is connected on a B wire to earth eyelet 
connector C0808-1.
RH front, rear and side direction indicator/hazard warning lamps
The feed from the RH direction indicator relay is connected on a GW wire from the 
passenger compartment fusebox to header C0289.
RH front
The feed is connected from the header C0289 on a GW wire to the front RH direction 
indicator/hazard warning lamp. The lamp is connected on a B wire, via header C1000 to 
earth eyelet connector C0558-1. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.127
RH rear
The feed is connected from header C0289, via header C0723, on a GW wire to the RH rear 
direction indicator/hazard warning lamp. The lamp is connected on a B wire to earth header 
C0706.
RH Side repeater
The feed is connected from header C0289 on a GW wire to the RH RH front side repeater 
lamp. The lamp is connected on a B wire, via header C1000, to earth eyelet connector 
C0558-1.
Trailer connection
The feed for the trailer connection is taken from header C0289, via header C0723, on a GW 
wire to the trailer pick-up. The trailer pick-up is connected on a B wire to earth eyelet 
connector C0808-1.
Hazard Warning Lamps Operation
The BCU supplies a reference voltage from pin C0663-12 on a GR wire to the hazard 
warning switch. When the hazard warning switch is operated an earth path is completed 
from the switch on a B wire, via header C0760, to earth header C0018 LHD/C0017 RHD. 
The completion of the earth signals the BCU that a request for hazard warning lamp 
operation has been made.
The BCU then sends a signal on an SK wire from pin C0661-1, via header C0293 LHD/
C0292 RHD, to the IDM in the passenger compartment fusebox. The SK wire is the serial 
data bus between the BCU, IDM and the instrument pack.
The signal is received by the IDM and interpreted as a request for hazard warning lamp 
operation. The IDM grants an earth path for the coils of the LH and RH direction indicator 
relays. The coils are energised by the feed from fuse 14 in the engine compartment fusebox, 
closing the relay contacts.
With the contacts closed, the feed from fuse 14 also passes through the relays and is 
connected, via resistors, from the passenger compartment fusebox to the direction 
indicators. The IDM controls the flasher operation by momentarily removing and restoring 
the earth for the relay coils, which opens and closes the contacts causing the indicator bulbs 
to flash on and off.
The resistor is used by the IDM to monitor the current drawn through the resistor by the 
direction indicator bulbs. If an indicator bulb fails, the IDM detects the drop in current draw 
across the resistor and operates the flasher relay at a faster speed. The faster flash is also 
transmitted to the instrument pack to inform the driver of the bulb failure. 
						

							DESCRIPTION AND OPERATION
4.128DISCOVERY SERIES II
The IDM operates both direction indicator lamps in the instrument pack on the serial data 
bus on the SK wire from the passenger compartment fusebox, via header C0293 LHD/
C0292 RHD, to the instrument pack.
The hazard warning lamp operation is the same as that described for the direction indicator 
lamps operation. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.129
INTERIOR LAMPS
DESCRIPTION
General
Interior illumination is provided by front, rear and load space lamps, ignition switch 
illumination, vanity mirror illumination and also includes an electrically operated interior rear 
view mirror (if fitted).
The front, rear and load space lamps and the ignition illumination operate from a direct feed 
from the battery, independent of the ignition switch position. The vanity mirrors and the 
interior rear view mirror operate with the ignition switch in position I or II.
The Body Control Unit (BCU) is programmed to operate the interior lamps and the ignition 
illumination for a predetermined period after a door has been opened or an unlock request 
is made with the handset.
Power is supplied to the interior rear view mirror when reverse gear is selected. This 
changes the mirror from its dipped to normal state for clarity of vision.
On Korean vehicles only, an additional link harness is used to provide a power supply from 
the rear interior lamp to the front interior lamp and infra-red sensor.
OPERATION
Interior Lamps Supply
Circuit supply
A feed from the battery positive terminal is connected on an R wire to the engine 
compartment fusebox where it passes through fusible links 1, 3, 7 and 8. Fusible links 1 and 
7 are connected in series.
A feed through fusible links 1 and 7 is connected to the contacts of the auxiliary circuits relay.
A feed from fusible link 3 is connected from the engine compartment fusebox to the 
passenger compartment fusebox on an NR wire. The feed passes through fuse 20 in the 
passenger compartment fusebox and is connected on a P wire to header C0289 LHD/C0294 
RHD.
A feed from fusible link 8 in the engine compartment fusebox is connected on an NW wire 
to the passenger compartment fusebox and from the fusebox to the ignition switch on an N 
wire.