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

							DESCRIPTION AND OPERATION
4.110DISCOVERY SERIES II
HEADLAMP LEVELLING
DESCRIPTION
General
The headlamp levelling is operated from a four position switch located on the fascia. The 
switch operates a motor located in each headlamp unit which moves the headlamp position 
to allow for changes in vehicle attitude due to load or passenger distribution.
The headlamp levelling operates when the side lamps or headlamps are on and is 
independent of the ignition switch position.
OPERATION
Headlamp Levelling 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 13.
When the lighting switch is in the side lamp or headlamp position, the feed from fusible link 
13 flows to the lighting switch on an NG wire. The feed flows through the lighting switch 
contacts and is connected to the passenger compartment fusebox on an R wire, where it 
passes through fuses 11 and 33.
Headlamp levelling motor supply
Fuse 11 supplies a feed to header C0288 LHD/C0286 RHD on an RB wire. Fuse 33 supplies 
a feed to the headlamp levelling switch on an RO wire, via header C0759.
From the header C0288 LHD/C0286 RHD, the feed is connected to the LH headlamp 
levelling motor on an RB wire. The earth path from the LH headlamp levelling motor is on a 
B wire to earth point C0564.
A second feed is connected to the RH headlamp levelling motor on a RB wire from the 
header C0288 LHD/C0286 RHD. The earth path from the RH headlamp levelling motor is 
on a B wire to earth header C0018. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.111
Headlamp Levelling Operation
At each of the four headlamp levelling switch positions, the contacts in the switch connect 
through resistors with differing values, which in turn provide four differing output voltages.
The output from the headlamp levelling switch is on a UY wire to header C0293 LHD/C0289 
RHD. The output is connected from header C0293 LHD/C0289 RHD on UY wires to both 
headlamp levelling motors. The headlamp levelling switch is connected on a B wire, via 
header C0760, to earth header C0018.
The difference in the voltage output from the headlamp levelling switch and the battery 
voltage is compared by a potentiometer in the LH/RH headlamp levelling motors. When the 
headlamp levelling switch is moved, the differing voltage causes the motor to operate until 
the potentiometer output equals the switch output. The motors stop and set the headlamps 
to a position which corresponds to the headlamp levelling switch position.
The input voltage to the headlamp levelling switch passes through the following resistors 
depending on switch position as follows:
Position 0 = 120 Ohm (R5) and 390 Ohm (R6)
Position 1 = 120 Ohm (R5), 20 Ohm (R4) and 390 Ohm (R6)
Position 2 = 120 Ohm (R5), 20 Ohm (R4), 100 Ohm (R3) and 390 Ohm (R6)
Position 3 = 120 Ohm (R5), 20 Ohm (R4), 100 Ohm (R3), 75 Ohm (R2) and 390 Ohm (R6). 
						

							DESCRIPTION AND OPERATION
4.112DISCOVERY SERIES II
LIGHTS ON ALARM
DESCRIPTION
General
The lights on alarm in the instrument pack operates when the drivers door is open and the 
side lamps are on. The system uses inputs from:
zThe drivers door switch
zThe lighting switch
A serial data bus allows communication between the the Body Control Unit (BCU), the 
Intelligent Driver’s Module (IDM) and the instrument pack.
OPERATION
Lights On Alarm Supply
Circuit supply
A feed from the battery positive terminal is connected on an R wire to the engine 
compartment fusebox where it is connected to fusible links 8 and 12 and fuse 13.
A feed from fusible link 12 is connected on an NG wire to the lighting switch.
A feed from fuse 13 is connected on a PN wire to pin C0660-13 on the BCU. A BCU system 
earth is provided by a B wire connected to earth header C0551.
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 to pin C0660-1 on the BCU by 
a GU wire.
Lights On Alarm Operation
When the lighting switch is moved to the side lamp or the headlamp position, the feed from 
fusible link 12 passes through the lighting switch contacts and is connected to the passenger 
compartment fusebox on an R wire.
The feed passes to the Intelligent Drivers Module (IDM), which is integral with the 
passenger compartment fusebox. This feed is used as a side lights on signal by the logic 
circuits in the IDM and BCU. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.113
The IDM is connected on the serial data bus link to pin C0661-1 on the BCU, and to the 
instrument pack via header C0293 LHD/C0292 RHD by an SK wire. When the drivers door 
is opened, the door switch contacts close, current flows from fuse 13 on a PN wire to pin 
C0660-13 on the BCU. From pin C0660-17 on the BCU the current flows on a PW wire via 
header C0287 LHD/C0285 RHD to the closed contacts of the drivers door switch. From the 
closed contacts of the drivers door switch the current flows on a B wire through splice joint 
A34 to earth header C0017 LHD/C0018 RHD (also via header C0288 on LH drive vehicles).
The current flow from fuse 13 is used by the logic signals of the BCU to generate a door open 
output. The BCU communicates along the serial data bus with the IDM and the Instrument 
pack.
The two door open and lights on signals generate the appropriate lights on alarm output 
to the instrument pack. The sounder in the instrument pack emits the lights on signal, and is 
earthed via the instrument pack.
For the system logic to generate a lights on alarm signal both the door open and lights on 
inputs must be present. If the light switch is turned off, the sidelights on signal is removed. 
With the loss of the input to the system the lights on alarm signal is cancelled by the logic 
circuits. If the door is closed when the side lights are on, the logic circuits will also cancel the 
lights on alarm signal. 
						

							DESCRIPTION AND OPERATION
4.114DISCOVERY SERIES II
HEAD/SIDE AND NUMBER PLATE LAMPS
DESCRIPTION
General
The side lamps, headlamps and number plate lamp are all controlled from a rotary lighting 
switch located on the column indicator lever. The side lamps and headlamps receive a 
permanent supply from the battery and operate independently of the ignition switch.
Two front headlamps contain the side lamp, dip and main beam bulbs. The side lamp bulbs 
are rated at 5 Watts. The dip beam bulbs are rated at 55 Watts and the main beam bulbs 
are rated at 60 Watts. A front side marker lamp is located in the outer part of each front 
indicator lense. Each side marker lamp is operated by one 2.2 Watt bulb.
A tail lamp and rear side marker lamp are located in a cluster on the outer panel of each E 
post. Each lamp cluster contains a tail lamp bulb and a side marker lamp bulb, both rated at 
5 Watts.
A number plate lamp is located in the tail door handle and contains one bulb rated at 5 Watts.
OPERATION
Head/Side and Number Plate 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 10, 12 and fuse 13.
A feed from fusible link 12 is connected from the engine compartment fusebox to the side 
lamp feed pin of the lighting switch on an NG wire.
A feed from fusible link 10 is connected from the engine compartment fusebox to the 
headlamp feed pin of the lighting switch on an NP wire.
A second feed from fusible link 10 in the engine compartment fusebox is connected to the 
passenger compartment fusebox on an U wire. The feed passes through fuse 5 in the 
passenger compartment fusebox and is connected to the contacts of the daylight running 
relay (if fitted).
A feed from fuse 13 in the engine compartment fusebox is connected to the passenger 
compartment fusebox on a PN wire. This feed supplies power to the coil of the daylight 
running relay (if fitted) and the Intelligent Drivers Module (IDM) which is integral with the 
passenger compartment fusebox. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.115
Side and Number Plate Lamps Operation
When the lighting switch is moved to the side lamps position, the feed from fusible link 12 in 
the engine compartment fusebox, passes through the switch contacts. The feed is 
connected on an R wire to the passenger compartment fusebox, where it passes through 
fuses 11 and 33.
When the lighting switch is moved to the headlamp position, the feed from fusible link 12 to 
the front and rear side lamps is maintained.
LH side, tail, side marker and number plate lamps
The feed from fuse 11 is connected from the passenger compartment fusebox to header 
C0288 LHD/C0286 RHD on an RB wire.
LH front side lamp
From the header C0288 LHD/C0286 RHD, a feed is connected on an RB wire to the LH front 
side lamp. The earth path from the LH front side lamp is on a B wire, via splice joint SJ2 to 
earth eyelet connector C0564-1.
LH tail and rear side marker lamps
A feed is taken from header C0288 LHD/C0286 RHD on an RB wire to header C0295. The 
feed continues from header C0295 on an RB wire to the LH tail lamp and the LH rear side 
marker lamp. The earth path from the LH tail lamp and the LH side marker lamp is on a B 
wire to earth header C0707.
LH front side marker lamp
A feed from header C0288 LHD/C0286 RHD is connected on an RB wire to the LH front side 
marker lamp. The earth path from the LH front side marker lamp is on a B wire, via header 
C0288 LHD/C1001 RHD, to earth header C0017 LHD or earth eyelet connector C0564-1 
RHD.
Number plate lamp
A feed from header C0295 is connected on an RB wire to the number plate lamp. The earth 
path from the number plate lamp is on a B wire to earth header C0706.
Trailer pick-up LH
A LH tail lamp feed from header C0295 is connected on an RB wire to connector interface 
C1481/C1482, and from the connector interface to the trailer pick-up on a B wire. The earth 
path for the trailer pick-up is on B wire to earth eyelet connector C0808-1.
RH side, tail and side marker lamps
The feed from fuse 33 is connected from the passenger compartment fusebox to header 
C0289 LHD/C0290 RHD on an RO wire. 
						

							DESCRIPTION AND OPERATION
4.116DISCOVERY SERIES II
RH front side lamp
From the header C0289 LHD/C0290 RHD, a feed is connected on an RO wire to the RH 
front side lamp. The earth path from the RH front side lamp is on a B wire, via splice joint 
SJ3 to earth eyelet connector C0559-1.
RH tail and rear side marker lamps
A feed is taken from header C0289 LHD/C0290 RHD on an RO wire to header C0723. The 
feed continues from header C0723 on a RO wire to the RH tail lamp and the RH rear side 
marker lamp. The earth path from the RH tail lamp and the RH rear side marker lamp is on 
a B wire to earth header C0706.
RH front side marker lamp
A feed from header C0289 LHD/C0290 RHD is connected on an RO wire to the RH front 
side marker lamp. The earth path from the RH front side marker lamp is on a B wire, via 
header C1001, to earth eyelet connector C0558-1.
Trailer pick-up RH
A RH tail lamp feed is taken from header C0289 LHD/C0290 RHD on an RO wire to header 
C0723. The feed continues from header C0723 on an RO wire to connector interface C1481/
C1482, and from the connector interface to the trailer pick-up on an N wire. The earth path 
for the trailer pick-up is on B wire to earth eyelet connector C0808-1.
Headlamps - Dip Beam Operation
When the lighting switch is moved to the headlamp position, the feed from fusible link 10 in 
the engine compartment fusebox passes through the switch contacts. The feed is connected 
on a UR wire to the passenger compartment fusebox, where it passes through fuses 9 and 
10.
LH headlamp
The feed from fuse 9 is connected on a UK wire from the passenger compartment fusebox 
to the LH headlamp and illuminates the LH dip beam bulb. The earth path from the LH 
headlamp is connected on a B wire to earth eyelet connector C0564-1.
RH headlamp
The feed from fuse 10 is connected on a UB wire from the passenger compartment fusebox 
to the RH headlamp and illuminates the RH dip beam bulb. The earth path from the RH 
headlamp is connected on a B wire to earth eyelet connector C0559-1. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.117
Headlamps - Main Beam Operation
When the lighting switch is moved to the flash or main position, the feed from fusible link 10 
in the engine compartment fusebox, passes through the switch contacts. The feed is 
connected on a UW wire to the passenger compartment fusebox, where it passes through 
fuses 3 and 22.
The IDM senses the headlamp main beam request and through internal circuitry, provides 
a feed, on a US wire, to the main beam warning lamp in the instrument pack. The main beam 
warning lamp is connected from the instrument pack to earth on a B wire to earth header 
C0551.
LH headlamp
The feed from fuse 3 is connected on a US wire from the passenger compartment fusebox 
to the LH headlamp and illuminates the LH main beam bulb. The earth path from the LH 
headlamp is connected on a B wire to earth eyelet connector C0564-1.
RH headlamp
The feed from fuse 22 is connected on a UO wire from the passenger compartment fusebox 
to the RH headlamp and illuminates the RH main beam bulb. The earth path from the RH 
headlamp is connected on a B wire to earth eyelet connector C0559-1.
Daylight Running Lamps Supply
The feed from fuse 13 in the engine compartment fusebox is connected to the coil of the 
daylight running relay and the IDM integral with the passenger compartment fusebox.
When the engine is started, the IDM senses, through internal circuitry, that the engine is 
running and provides an earth for the daylight running relay coil. The energised coil closes 
the contacts of the daylight running relay allowing the feed from fuse 5 in the passenger 
compartment fusebox to pass through the relay contacts.
Daylight Running Lamps Operation
Canadian vehicles
The feed from the daylight running relay contacts flows from the passenger compartment 
fusebox and is connected to a 0.75 Ohm in-line resistor on an RU wire. The feed from the 
in-line resistor is reduced to 6.7 V and reconnected to the passenger compartment fusebox 
on a UY wire. The feed is connected to fuses 3 and 22 in the passenger compartment 
fusebox, where it operates both headlamp main beam bulbs at reduced power.
Scandinavian vehicles
The feed from the daylight running relay contacts flows from and back to the passenger 
compartment fusebox on a UY wire. The feed is connected to fuses 9 and 10 in the 
passenger compartment fusebox, where it operates both headlamp dip beam bulbs. 
						

							DESCRIPTION AND OPERATION
4.118DISCOVERY SERIES II
FRONT FOG LAMPS
DESCRIPTION
General
The front fog lamps are controlled by a non-latching switch located on the left hand side of 
the instrument pack. Two front fog lamps are located below the front bumper. Front fog lamp 
operation is monitored by the Body Control Unit (BCU) which only allows the front fog lamps 
to operate when the side lamps or headlamps are on.
When the side lamps, headlamps or ignition is turned off, the front fog lamps are 
extinguished. When the side or headlamps are switched on again, the front fog lamps will 
not operate until reselected using the switch. If the rear fog guard lamps are switched on, 
switching off the front fog lamps will also switch off the rear fog guard lamps.
The front fog lamp switch is illuminated when the side lights are switched on. Each front fog 
lamp bulb is rated at 21 Watts.
OPERATION
Front Fog 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 1, 7, 8 and 13 and fuses 3 and 
13. Fusible links 1 and 7 and fusible link 1 and fuse 3 are connected in series.
A feed from fusible link 13 is connected by an NG wire to the lighting switch.
A feed from fuse 3 is connected to the front fog lamp relay in the engine compartment 
fusebox. A feed from fusible link 7 is connected to the auxiliary circuits relay in the engine 
compartment fusebox.
A feed from fuse 13 is connected by a PN wire to the passenger compartment fusebox. This 
feed is connected to the Intelligent Driver Module (IDM) which is integral with the passenger 
compartment 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. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.119
Ignition switch supply
With the ignition switch in position I, the feed from fusible link 8 flows through the ignition 
switch to the passenger compartment fusebox on a LGW wire. The feed continues through 
fuse 26 in the passenger compartment fusebox and is connected by an LG wire to the 
engine compartment fusebox and the coil of the auxiliary circuits relay. The auxiliary circuits 
relay coil is connected to earth header C0018, via header C0286 LHD/C0288 RHD on a B 
wire.
In this condition, the auxiliary circuits relay is energised and the contacts close, allowing the 
feed from fusible link 7 to pass through the closed contacts to the coil of the front fog lamp 
relay.
With the ignition switch in position II, a second feed from fusible link 8 flows from 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 the IDM.
In this condition, one of two electronic 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 Operation
The feed from fuse 13 passes through the two closed IDM switches and 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.