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

							DESCRIPTION AND OPERATION
4.30DISCOVERY SERIES II
Folding Mirrors Operation
When the switch is moved to the fold position, an earth path is completed on a UB wire from 
the ECU pin C0907-5 to the mirror switch. The earth continues through the switch contact 
and is connected on a B wire to earth header C0018.
The ECU supplies a feed to the RH folding mirror motor from pins C0907-1 or C0907-3 on 
O or OR wires to the motor. Depending on motor direction required to fold mirrors in or out, 
the earth from each motor is on either the O or the OR wire back to the ECU.
The ECU supplies a feed to the LH folding mirror motor from pins C0907-7 or C0907-9 on 
YR or Y wires to the motor. Depending on motor direction required to fold mirrors in or out, 
the earth from each motor is on either the YR or the Y wire back to the ECU. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.31
ELECTRIC SEATS
DESCRIPTION
Adjustment
The electrically powered front seats are operated by four electric motors which control the 
seat base rear up/down, seat base front up/down, seat base forward/rearward and seat 
squab recline. The seats are operated by switches and controlled by the Body Control Unit 
(BCU). The seats operate when the ignition switch is in position I or II or for a predetermined 
period when the drivers door is open.
A electrically powered lumbar adjustment in each seat is operated by a single motorised 
pump and a solenoid located on the seat squab frame. The pump inflates a cushion in the 
seat squab and the solenoid operates a valve to deflate the cushion. The seat cushion and 
seat squab also contain heater elements.
A seat switch pack is located on each side of the centre console. Each switch pack 
comprises two non-latching switch levers. The horizontal lever has three, two position 
switches which control the seat cushion forward and rearward movement and also the seat 
cushion front and rear height adjustment. The vertical switch has two, two position switches 
which control the seat squab recline function and also the lumbar adjustment.
The power supply to each seat switch pack is supplied from a power seat relay located on 
the underside of each seat frame. The feed from the relay is protected by a fuse located in 
a satellite fuse block adjacent to the power seat relay. The fuse block also contains two 
additional fuses which protect the feeds to the lumbar pump and solenoid.
Heating
The heated seat elements for each seat are supplied power from a seat heat module located 
on the underside of the seat frame. The seat heat module provides consistent temperature 
control of the seat heater elements. A negative temperature coefficient variable resistor is 
located in the seat cushion heater element. The resistor changes its resistance as the seat 
cushion temperature increases or decreases. The resistance is monitored by electronics 
within the seat heat module, which raises or lowers the power supplied to the elements and 
controls the element temperature between 26 and 36 degrees C (79 and 97 degrees F).
The heated seat elements are operated by a latching seat heater switch for each seat 
located in the centre console between the two rear window switches. The heated seats only 
operate when the ignition switch is in position II. 
						

							DESCRIPTION AND OPERATION
4.32DISCOVERY SERIES II
OPERATION
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, 5, 7 and 8. Fusible links 1 and 
5 and 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.
A feed from fusible links 1 and 5 is connected on an NG wire to connector C0255-5/C0751-
1 interface. From connector C0751-1, the feed continues on an NP wire to the coil and 
contacts of the LH power seat relay. The earth path from the relay coil is connected on an 
OP wire to the BCU pin C0663-3, via header C0724.
A second feed from fusible links 1 and 5 is connected on an NP wire to the coil and contacts 
of the RH power seat relay. The earth path from the relay coil is connected on an OP wire 
to the BCU pin C0663-3, via header C0724.
The BCU completes the earth path when ignition I or II or driver’s door open is sensed.
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 I or II, the feed from fusible link 8 passes through the 
ignition switch to the passenger compartment fusebox on an LGW wire.
The feed continues through fuse 26 in the passenger compartment fusebox and is 
connected from the fusebox on an LG wire to the coil of the auxiliary circuits relay in the 
engine compartment fusebox. This feed energises the relay coil, closing the relay contacts. 
The relay coil is earthed on a B wire, via header C0286 LHD/C0288 RHD, to earth header 
C0018.
Seat Heating Operation
With the auxiliary circuits relay energised, the feed from fusible links 1 and 7 passes through 
the relay contacts and is connected to the passenger compartment fusebox on a WG wire 
where it passes through fuse 15.
From the passenger compartment fusebox, the feed is connected to header C0761 on an 
LGW wire. From the header C0761, the feed separates into two LGW wires which are 
connected to the LH and RH seat heater switches.
From the LH seat heater switch the feed is connected on a US wire to connector C0225-1/
C0751-1 interface. From connector C0751-1 the feed continues on an OW wire to the LH 
seat heat module. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.33
From the RH seat heater switch the feed is connected on a UK wire to connector C0253-1/
C0751-1 interface. From connector C0751-1 the feed continues on an OW wire to the RH 
seat heat module.
Power is supplied to the electronics within the LH or RH seat heat module by the feed from 
the LH or RH seat heater switch. This allows the feed to pass through the module and is 
connected to the LH or RH seat cushion heater on a K wire. The LH or RH seat squab heater 
is connected in series from the LH or RH seat cushion heater on a KW wire. The LH and RH 
seat squab heaters are connected to earth header C0708 on B wires via splice joint 1.
The earth from the LH or RH seat heat module is connected on an LG wire to a temperature 
variable resistor contained within each of the LH and RH seat cushion heaters. As the 
temperature of the seat cushion heater increases, the resistance of the resistor changes. 
This is sensed by the seat heat module which varies the power supplied to the LH and RH 
seat cushion heaters, raising or lowering their temperature accordingly.
The resistors are connected to the LH and RH seat heat module on B wires and from the LH 
and RH seat heat modules to earth header C0708 on B wires via splice joint 1.
Seat Adjustment Operation
With the ignition switch in position I or II or the driver’s door open, the BCU provides an earth 
path for the coils of the LH and RH power seat relays, energising the relays and closing the 
contacts.
The feeds from fusible links 1 and 7 pass through the relay contacts and connect on WN 
wires to the LH and RH satellite fuse blocks. The feed passes through fuse 2 in each satellite 
fuse block and is connected to the LH and RH seat switch packs on WR wires.
Each of the four seat motors are connected to the LH or RH seat switch pack by two wires. 
The operation of the switches can supply the feed from fuse 2 into either of the wires to 
operate the motors in either direction. The wire connections to each motor from the LH or 
RH switch pack is as follows:
zThe LH and RH rear up/down seat motors are connected on U and NY wires 
respectively.
zThe LH and RH seat motor forward/rearward motors are connected on R and GY wires 
respectively.
zThe LH and RH front up/down seat motors are connected on Y and W wires 
respectively.
zThe LH and RH back recline forward/rearward seat motors are connected on O and S 
wires respectively. 
						

							DESCRIPTION AND OPERATION
4.34DISCOVERY SERIES II
Lumbar Operation
When the lumbar inflate switch is operated, the feed from fuse 2 in the LH or RH satellite 
fuse block is connected from the LH or RH seat switch pack and connected to fuse 3 in the 
LH or RH satellite fuse block on a P wire. From fuse 3, the feed is connected to the LH or 
RH lumbar pump on a P wire.
When the lumbar deflate switch is operated, the feed from fuse 2 in the LH or RH satellite 
fuse block is connected from the LH or RH seat switch pack to fuse 4 in the LH or RH satellite 
fuse block on a PS wire. From each fuse 4 the feed is connected to the LH or RH lumbar 
pump solenoid on a PS wire.
The earth from the LH and RH lumbar pumps is on B wires to earth header C0708 via splice 
joint 1. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.35
MANUAL SEATS
DESCRIPTION
General
On vehicles with manual seats and seat heaters, the temperature is controlled by a 
thermostatic switch located in the seat cushion. The thermostat disconnects the power 
supply when the thermostat reaches 36 degrees C (97 degrees F) and restores the power 
supply when the temperature is below 26 degrees C (79 degrees F).
OPERATION
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.
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 I or II, the feed from fusible link 8 passes through the 
ignition switch to the passenger compartment fusebox on an LGW wire.
The feed continues through fuse 26 in the passenger compartment fusebox and is 
connected from the fusebox on an LG wire to the coil of the auxiliary circuits relay in the 
engine compartment fusebox. The feed energises the relay coil, closing the relay contacts. 
The relay coil is earthed on a B wire, via header C0286 LHD/C0288 RHD, to earth header 
C0018.
Seat Heating Operation
with the auxiliary circuits relay energised, the feed from fusible links 1 and 7 passes through 
the relay contacts and is connected to the passenger compartment fusebox on a WG wire 
where it passes through fuse 15.
From the passenger compartment fusebox, the feed is connected to header C0761 on an 
LGW wire. From the header C0761, the feed separates into two LGW wires which are 
connected to the LH and RH seat heater switches. 
						

							DESCRIPTION AND OPERATION
4.36DISCOVERY SERIES II
LH seat
From the LH seat heater switch the feed is connected on a US wire to connector interface 
C0255-1/C0751-1. From the interface the feed continues on an R wire to the LH seat 
cushion heater. The feed passes through the thermostatic switch and the cushion heater 
and is connected in series on a B wire to the LH seat squab heater. The seat squab heater 
is connected on a B wire to earth header C0708.
RH seat
From the RH seat heater switch the feed is connected on a UK wire to connector interface 
C0253-1/C0751-1. From the interface the feed continues on an R wire to the RH seat 
cushion heater. The feed passes through the thermostatic switch and the cushion heater 
and is connected in series on a B wire to the RH seat squab heater. The seat squab heater 
is connected on a B wire to earth header C0708. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.37
DIAGNOSTIC SOCKET
DESCRIPTION
General
The diagnostic socket is located below the facia on the drivers side. The connector is 
constructed to ISO standard and allows the attachment of TestBook/T4 or any other ISO 
standard scantool.
The diagnostic socket allows diagnostic information stored in any of the ECU’s listed below 
to be retrieved. It also allows engine tuning and fault diagnosis to be carried out.
OPERATION
Diagnostic Socket 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 3.
The feed from fusible link 3 is connected by an NR wire to the passenger compartment 
fusebox where it passes through fuse 20.
The feed from fuse 20 is connected to the diagnostic socket, via header C0294 by a P wire.
Diagnostic socket earth connection - LHD vehicles
The diagnostic socket is connected to two earth headers C0551 and C0017 by B wires.
Diagnostic socket earth connection - RHD vehicles
The diagnostic socket is connected to earth header C0551 by a B wire. The diagnostic 
socket is also connected with a B wire through header C0291 to earth header C0017.
Diagnostic Socket Connections
Engine Control Module (ECM)
The ECM for V8 and Td5 variants is connected to header C0286 on a K wire. The connection 
continues from the header C0286 to the diagnostic socket on a K wire.
Body Control Unit (BCU)
The BCU is connected to header C0286 on a K wire. The connection continues from header 
C0286 to the diagnostic socket on a K wire.
Electronic Automatic Transmission (EAT) ECU
The EAT ECU is connected to header C0286 on a K wire. The connection continues from 
the header C0286 to the diagnostic socket on a K wire. 
						

							DESCRIPTION AND OPERATION
4.38DISCOVERY SERIES II
Self Levelling/Anti-Lock Brake System (SLABS) ECU
The SLABS ECU is connected to header C0286 on a K wire. The connection continues from 
the header C0286 to the diagnostic socket on a K wire.
Active Cornering Enhancement (ACE) ECU
The ACE ECU is connected to header C0286 on a K wire. The connection continues from 
the header C0286 to the diagnostic socket on a K wire.
Cruise control ECU - V8 engines only
The cruise control ECU is connected to header C0286 on a K wire. The connection 
continues from the header to the diagnostic socket on a K wire.
Airbag DCU
The airbag DCU is connected to header C0286 on a K wire. The connection continues from 
the header C0286 to the diagnostic socket on a K wire.
Fuel Burning Heater (FBH) - Td5 vehicles (if fitted)
The fuel burning heater is connected to the diagnostic socket on a R wire. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.39
BODY CONTROL UNIT (BCU)
DESCRIPTION
General
The BCU communicates with and controls a large number of functions on the vehicle. Refer 
to BCU circuit diagram for BCU connection details.
For BCU power supplies refer to Power Distribution circuits.