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

							DESCRIPTION AND OPERATION
4.100DISCOVERY SERIES II
Slow speed operation
Operation of the front screen wash/wipe switch to the slow wipe position, connects the feed 
from fuse 19 in the passenger compartment fusebox to the front screen wash/wipe switch 
on a GS wire, via header C0292.
The feed passes through the slow wipe switch contacts and is connected to the windscreen 
wiper motor on an RLG wire. The windscreen wiper motor is connected to earth header 
C0017, via header C0288 on a B wire. The feed is connected to the slow speed brushes 
within the motor and operates the motor at slow speed.
Fast speed operation
Operation of the front screen wash/wipe switch to the fast wipe position, connects the feed 
from fuse 19 in the passenger compartment fusebox to the front screen wash/wipe switch 
on a GS wire, via header C0292.
The feed passes through the fast wipe switch contacts and is connected to the windscreen 
wiper motor on a ULG wire. The windscreen wiper motor is connected to earth header 
C0017, via header C0288 on a B wire. The feed is connected to the fast speed brushes 
within the motor and operates the motor at fast speed.
Intermittent operation
Operation of the front screen wash/wipe switch to the intermittent position allows a feed from 
fuse 19 to pass on a GS wire, through header C0292, to the wash/wipe switch. The feed 
passes through the switch contacts and is connected on an LGG wire to pin C0660-21 on 
the BCU. The BCU interprets the signal as an intermittent wiper request and signals the IDM 
via the serial data bus.
The feed from fuse 19 is also connected from the header C0292 on a GS wire to the wiper 
motor, where it passes through the park switch. The feed is connected from the wiper motor 
on a WLG wire to the passenger compartment fusebox.
The feed passes through the front wiper relay contacts and is connected from the fusebox 
on an LGP wire to the wash/wipe switch. The feed passes through the switch contacts and 
is connected from the switch on an RLG wire to the wiper motor. This operates the wiper 
motor moving it from the park position.
Simultaneously, the feed from fuse 19, via header C0292 and the wiper motor park switch, 
is also connected to the coil of the front wiper relay. The IDM grants an earth for the relay 
coil moving the contacts. This allows a direct feed from fuse 19 to pass through the relay and 
is connected from the fusebox on an LGP wire to the wash/wipe switch. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.101
The feed passes through the switch contacts and is connected from the switch on an RLG 
wire to the wiper motor. When the wiper motor reaches the park position, the park switch 
moves to power the wipers to their park position. The IDM removes the earth for the relay 
coil preventing further wiper operation.
The BCU pin C0660-21 is connected on a WLG wire to the wiper delay switch, which is 
connected on a B wire to earth header C0551. The BCU provides an output voltage which 
it uses to measure the resistance through the delay switch.
The resistance determines the delay required and the BCU transmits a signal, via the serial 
data bus to the IDM, for the front wiper relay to be operated.
Flick wipe operation
When the switch stalk is momentarily pushed downwards and released, a feed from fuse 19 
is connected on a GS wire to header C0292. From the header the feed is connected on a 
GS wire to the wash/wipe switch. From the switch the feed is connected on a ULG wire to 
fast speed brushes in the motor.
This momentary feed to the motor is enough to move the motor, moving the park switch from 
the park position. When the stalk switch is released, the feed from the wash/wipe switch is 
removed.
The motor is now powered by a feed from fuse 19, via header C0292, on a GS wire to the 
motor. The feed passes through the park switch and is connected from the motor on a WLG 
wire to the front wiper relay.
The feed passes through the wiper relay and is connected from the fusebox on an LGP wire 
to the wash/wipe switch, through the switch contacts and is connected from the switch on 
an RLG wire to the wiper motor slow speed brushes. The motor operates at slow speed. 
When the wiper motor reaches the park position the park switch moves, removing the feed 
from fuse 19 and the motor stops.
If the switch stalk is pushed downwards and held, the feed from fuse 19 is passed directly 
from the switch to the motor fast speed brushes causing the motor to operate at fast speed 
for as long as the switch is held. When the switch is released, the motor completes its cycle 
to the park position powered through the park switch to the motor slow speed brushes 
causing the motor to operate at slow speed. 
						

							DESCRIPTION AND OPERATION
4.102DISCOVERY SERIES II
Washer operation
When the switch stalk is pulled, a feed from fuse 19 is connected on a GS wire, via header 
C0292, to the wash/wipe switch. The feed passes through the washer switch contacts and 
is connected from the switch on an LGO wire, through header C0289, to the washer pump 
and the BCU pin C0661-11. The feed operates the washer pump motor which is connected 
on a B wire to earth eyelet connector C0564-1.
The feed to the BCU is interpreted by the BCU as a wash/wipe request. If the washer switch 
is held for longer than 0.4 seconds the BCU signals the IDM through the serial data bus to 
energise the front wiper relay. A feed from fuse 19 passes through the relay and is 
connected from the fusebox on a LGP wire to the wash/wipe switch.
The feed passes through the switch and is connected on an RLG wire to the motor slow 
speed brushes. The IDM energises the front wiper relay for 4 seconds allowing the screen 
to be cleared. After 4 seconds the IDM removes the earth path for the relay coil, causing the 
wipers to return to the park position.
Powerwash operation
When the headlamps are turned on, a feed from fusible link 10 passes from the engine 
compartment fusebox on an NP wire to the lighting switch. The feed passes through the 
switch and is connected on a UR wire to the IDM. The IDM senses that the headlamps are 
on and signals the BCU via the serial data bus.
When washer operation is requested, the BCU grants an earth path for the powerwash relay 
in the engine compartment fusebox. The earth path is on an LG wire from the fusebox to pin 
C0662-12 on the BCU. The relay coil is energised by the feed from the auxiliary circuits relay 
allowing the feed from fuse 4 to pass through the relay contacts.
The feed is connected from the fusebox on an LGR wire to the powerwash pump. The 
powerwash pump is connected on a B wire to earth eyelet connector C0564-1. The BCU 
only energises the powerwash relay coil for 0.5 seconds on every alternate washer request. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.103
REAR WIPERS AND WASHERS
DESCRIPTION
General
The rear wiper is operated from a latching push button switch located on the right hand side 
of the instrument pack. The rear wash/wipe is operated from a non-latching push button 
switch also located on the right hand side of the instrument pack. The rear wiper park facility 
operates with the ignition switch in positions I or II. The rear wiper and washer only operates 
with the ignition switch in position II.
The rear wiper and washer functions are controlled by the Body Control Unit (BCU) and the 
Intelligent Driver’s Module (IDM).
The rear wiper is operated by an electric motor located in the tail door. The rear washer is 
operated by an electric pump located on the reservoir in the left hand front wheel arch.
Operation of the rear wiper switch causes the wiper to complete two full cycles. The wiper 
then operates intermittently until selected off. The frequency of the intermittent operation is 
controlled by the front wiper delay switch on the column stalk. The intermittent delay is twice 
that of the front delay selected. The BCU determines the resistance through the delay switch 
and functions the rear wiper at the required interval, depending on the front wiper delay 
switch position.
Operation of the rear washer switch causes the washer motor to operate for as long as the 
switch is operated. The wiper will also operate while the switch is depressed and will operate 
for a further 4 seconds after the switch is released.
If the front wipers are selected on and reverse gear is engaged, the rear wiper will operate 
continuously until reverse gear is disengaged.
If the front wipers are selected on intermittent and reverse gear is engaged, the rear wiper 
will wipe continuously for 4 seconds. It will then change to intermittent operation but the 
delay will be the same as that for front wipers. When reverse gear is disengaged, the rear 
wiper will stop at the park position. 
						

							DESCRIPTION AND OPERATION
4.104DISCOVERY SERIES II
OPERATION
Rear Wiper and Washers 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, 7 and 8. Fusible links 1 and 
7 are connected in series.
A feed from fusible links 1 and 7 is connected to the contacts of the auxiliary circuits relay 
located in the engine compartment fusebox.
A feed from fusible link 8 is connected from the fusebox, 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 I, the feed from fusible link 8 passes through the ignition 
switch to the passenger compartment fusebox (P101) on an LGW wire, where it passes 
through fuse 26. From fuse 26, the feed passes to the engine compartment fusebox on an 
LG wire where it connects to the coil of the auxiliary circuits relay.
The coil of the auxiliary circuits relay is connected from the engine compartment fusebox on 
a B wire to earth header C0018, via header C0286 LHD/C0288 RHD. The feed from the 
ignition switch energises the auxiliary circuits relay coil, closing the relay contacts.
The feed from fusible links 1 and 7 passes through the closed contacts of the auxiliary 
circuits relay. The feed is connected from the relay on a WG wire from the engine 
compartment fusebox to the passenger compartment fusebox, where it passes through fuse 
18.
From fuse 18 the feed is connected to the contacts of the rear wiper relay and to the rear 
screen wiper motor on a GLG wire. The feed to the motor supplies power through the park 
switch to allow the wiper to move to the park position. The rear screen wiper motor is 
connected on a B wire to earth header C0706, via splice joints A39/A109.
With the ignition switch in position II, the feed from fusible link 8 passes through the ignition 
switch to the passenger compartment fusebox on an W wire, where it passes through fuse 
30. From fuse 30 the feed is connected on a GLG wire, via splice joint A128, to the rear 
screen washer switch.
A second feed from the ignition switch is connected on a Y wire to the passenger 
compartment fusebox where it passes through fuse 25. From fuse 25 the feed is connected 
on a GY wire to the reverse lamp switch (manual transmission) or the starter inhibitor/
reverse lamp switch (automatic transmission). 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.105
The reverse lamp switch is connected is connected on a GN wire, via header C0287 LHD/
C0294 RHD, to pin C0661-8 on the BCU. When the reverse lamp switch is operated, the 
feed from fuse 25 passes through the switch to the BCU which uses the signal to function 
the rear wiper accordingly.
Rear Wipers and Washers Operation
The IDM is connected to pin C0661-1 of the BCU via header C0293 LHD/ C0292 RHD on 
an SK wire. This connection is the serial data bus between the IDM and the BCU.
Wiper operation
When the rear wiper switch is operated an earth path is completed on an OB wire from pin 
C0662-3 of the BCU to the switch, and a B wire from the switch to earth header C0018 via 
header C0760. The completed earth path provides a signal to the BCU that rear wiper 
operation has been requested.
The BCU sends a signal through the serial data bus to the IDM to commence wiper 
operation. The IDM provides a power supply and earth for the coil of the rear wiper relay in 
the passenger compartment fusebox, which energises closing the relay contacts.
With the relay contacts closed, a feed from fuse 18 passes through the relay and is 
connected on an NG wire to the park switch in the wiper motor. This feed initially operates 
the motor until the park switch contact is broken. On each revolution, the motor is moved 
from the park position by the feed from the park switch. When the park switch contact moves 
the feed from the relay is disconnected and the motor completes the cycle on a feed from 
fuse 18 on a GLG wire to the motor.
When the rear wiper switch is moved to the off position, the earth path to the BCU is 
removed. The BCU sends a signal through the serial data bus to the IDM which removes the 
power and earth for the rear wiper relay coil. The feed through the relay to the park switch 
is removed causing the motor to stop when it reaches the end of its cycle.
Intermittent operation
The BCU operates the rear wiper continuously for 4 seconds, after which the wiper operates 
at a delay interval set by the position of the wiper delay switch on the column stalk.
The delay switch is connected on a WLG wire to pin C0661-21 on the BCU and on a B wire 
to earth header C0551. The BCU provides an output voltage which it uses to measure the 
resistance through the delay switch. The resistance determines the delay required and the 
BCU transmits a signal, via the serial data bus to the IDM, for the rear wiper relay to be 
operated. 
						

							DESCRIPTION AND OPERATION
4.106DISCOVERY SERIES II
Washer operation
When the rear screen washer switch is operated, a feed from fuse 30 in the passenger 
compartment fusebox is connected on a GLG wire to the switch. The feed passes through 
the switch contacts and is connected on an LGS wire, via header C0293, to the rear screen 
washer pump. The pump is connected on a B wire to earth eyelet connector C0564-1. The 
feed is also connected from the header C0293 on an LGS wire to pin C0660-20 on the BCU.
The pump operates for as long as the switch is pushed. The connection to the BCU signals 
that rear washer operation has been requested. The BCU signals the IDM to energise the 
rear wiper relay to operate the rear wiper 0.5 seconds after the request has been made.
Reverse wipe operation
When reverse gear is selected, a feed from fuse 25 in the passenger compartment fusebox 
is connected on a GY wire to the reverse lamp switch (manual transmission) or the starter/ 
inhibitor/ reverse lamp switch (automatic transmission).
The feed passes through the switch contacts and is connected on a GN wire, via header 
C0287 LHD/C0294 RHD, to pin C0661-8 on the BCU. The BCU interprets the signal and 
signals the IDM via the serial data bus to energise the rear wiper relay. The operation of the 
rear wiper is dependant on front wiper selection as described in Description. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.107
BRAKE/REVERSE LAMPS
DESCRIPTION
Brake Lamp Description
The brake lamps are operated by a switch mounted on the pedal box. The switch, when 
operated, supplies power to two brake lights located in the tail lamp units and a high 
mounted brake light. All brake light bulbs are rated at 21 Watts. A feed is provided to the 
trailer pick-up (if fitted) when the brake switch is operated. When the brake light switch is in 
the open position feeds are routed through the switch contacts to give:
Automatic V8 vehicles: A feed to the cruise control ECU for cruise control operation.
Manual V8 vehicles: A feed to the clutch pedal switch for cruise control operation.
Td5 vehicles: A feed to the Engine Control Module (ECM) for cruise control operation.
Reverse Lamp Description
The reverse lamps are operated by a switch located in the vehicle gearbox. The switch, 
when operated, supplies power to two reverse lamps located in the tail lamp units. The 
reverse lamp bulbs are rated at 21 Watts. When the reverse lamp switch is operated an input 
is also provided to:
zThe Body Control Unit (BCU) for rear wiper operation.
zThe interior mirror for selection of normal mirror position.
zThe trailer pick-up (if fitted).
Automatic vehicles have a dual function starter inhibitor and reverse light switch. The 
inhibitor function prevents the engine from cranking if reverse gear is selected.
OPERATION
Brake/Reverse Lamp 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.
Ignition switch supply
In the engine compartment fusebox, a feed from fusible link 8 is connected to the passenger 
compartment fusebox by an NW wire. The feed passes through the fusebox and is 
connected to the ignition switch by an N wire.
When the ignition is switched on to position II, a feed from the ignition switch is connected 
to the passenger compartment fusebox by a Y wire and passes through fuse 25. 
						

							DESCRIPTION AND OPERATION
4.108DISCOVERY SERIES II
Brake Lamp Operation
A feed from fuse 25 in the passenger compartment fusebox is connected by a GO wire to 
the brake pedal switch.
When the brake pedal switch is operated, the switch contact closes and allows current to 
flow on a GP wire, from the switch, through header joints C0287 LHD/C0290 RHD and 
C0295. From header C0295 a connection on a GP wire allows current flow to the LH brake 
lamp. Another connection from header C0295 on a GP wire, goes through header C0723 
and allows current flow to the RH tail lamp. A second connection from header C0723 on a 
GP wire, allows current flow to the high mounted brake lamp.
A third connection from earth header C0723 is connected to the trailer pick-up (if fitted) on 
a GP wire. The trailer pick-up is earthed on a B wire to earth point C0808.
The LH brake lamp is earthed on a B wire to an earth header C0707. The RH brake lamp is 
earthed on a B wire to an earth header C0706. The high mounted brake lamp is earthed on 
a B wire to earth header C0706.
When the contacts of the brake pedal switch are open the connection from fuse 25 in the 
passenger compartment fuse box supplies:
Automatic V8 vehicles: A feed on a PG wire to the cruise control ECU.
Manual V8 vehicles: A feed on a OG wire to the clutch pedal switch.
Td5 vehicles: A feed on an OG wire to the ECM for cruise control operation.
Reverse Lamp Operation
Manual transmission
A feed from fuse 25 is connected by a GY wire to the reverse lamp switch.
Automatic transmission
A feed from fuse 25 is connected by a GY wire to the automatic transmission starter inhibitor/
reverse light switch.
All models
When the reverse lamp switch is operated, the switch contact closes and allows current flow 
on a GN wire, from the switch, through two headers C0287 LHD/C0294 RHD and C0295, to 
the RH reverse lamp and the LH reverse lamp. The LH reverse lamp is earthed on a B wire 
to earth header C0707. The RH reverse lamp is earthed on a B wire to earth header C0706. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.109
When the reverse lamps are on, a splice joint A13 between headers C0287 LHD/C0294 
RHD and C0295, gives a feed on a GN wire to the interior mirror.
The feed supplied to the interior mirror will change the interior mirror to the undipped 
condition, if the interior mirror is dipped. The interior mirror will remain in the undipped 
condition as long as a feed is supplied. This feature ensures that the interior mirror is in the 
undipped condition when reverse gear is selected.
A GN wire from header C0287 LHD/C0294 RHD is connected to the BCU. When the reverse 
lamp switch is operated, this feed is used by the BCU logic circuits to enable rear wiper 
operation.