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

							EARTH POINTS AND HEADER JOINTS
3.2DISCOVERY SERIES II 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.1
DE SCRIP TION AND OPERATIONANTI-THEFT ALARM
DESCRIPTION
Anti-Theft Alarm Description
The anti-theft alarm system is controlled by the Body Control Unit (BCU). The system alarms 
and disables the vehicle and monitors the vehicle status using door switches and ultrasonic 
sensors. The BCU also operates in conjunction with the Engine Control Module to disable 
the engine operation. Refer to the Workshop Manual for detailed Description and Operation 
of the anti-theft system.
When an alarm is triggered, the BCU operates the vehicle horns, an alarm sounder unit and/
or a Battery Back Up Sounder (BBUS), depending on market, to produce an audible 
warning. In some markets, the BCU also operates the direction indicators to produce a visual 
warning when the system is armed and disarmed and/or an alarm is triggered.
On Korean vehicles only, the RF remote handset and receiver are replaced by an infra-red 
handset and receiver. The infra-red signal is received by the infra-red receiver located in the 
front interior lamp. An additional link harness is used as shown on the circuit diagrams and 
described in the following circuit operation. The feed for the receiver is taken from the rear 
interior lamp circuit - refer to interior illumination description in this manual for details.
OPERATION
Anti-Theft Alarm Supply
Circuit supply
A feed from the battery positive terminal is connected on an R wire to the engine 
compartment fusebox. The feed passes through fusible links 3 and 8 and fuses 13 and 16.
The feed from fusible link 3 is connected on an NR wire to fuses 2, 20 and 21 in the 
passenger compartment fusebox. Fuse 21 supplies a feed to the contacts of the alarm 
sounder relay in the passenger compartment fusebox.
Fuse 21 also supplies a feed to the BBUS (where fitted), on a PB wire via header C0292, to 
keep the BBUS battery charged. If this feed is disrupted while the alarm system is armed, 
the BBUS is automatically activated. The BBUS is connected to earth header C0706 on a B 
wire.
The 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. The feed from fuse 16 is 
connected to the coil and contacts of the horn relay located in the engine compartment 
fusebox. 
						

							DESCRIPTION AND OPERATION
4.2DISCOVERY SERIES II
Where an alarm sounder unit is installed, a feed from fuse 13 is connected on a PN wire from 
the engine compartment fusebox to the passenger compartment fusebox. The feed passes 
through a diode and is connected to the coil of a relay integrated into the fusebox. The relay 
controls a power feed to the alarm sounder unit. Activation of the relay is controlled by the 
BCU via the IDM. The BCU communicates with the IDM using serial data messages on a 
SK wire via header C0292.
Ignition switch supply
When the ignition switch is in position II, the feed from fusible link 8 passes through the 
ignition switch to the passenger compartment fusebox on a Y wire where it passes through 
fuse 29. From fuse 29, the feed is connected on a GU wire to provide an ignition on supply 
to the BCU.
When the ignition switch is in the crank position III, the feed from fusible link 8 passes 
through the ignition switch to the passenger compartment fusebox on a WR wire and passes 
through fuse 23.
From fuse 23 the feed is connected on a WR wire to the coil of the starter relay in the engine 
compartment fusebox. The coil of the starter relay is connected on a BO wire from the 
engine compartment fusebox to pin C0662-5 on the BCU.
A second feed from fuse 23 is also connected on a WR wire to pin C0663-1 on the BCU. 
When the ignition switch is in crank position III, this feed signals the BCU to provide an earth 
path for the starter relay coil. This energises the coil closing the relay contacts and supplying 
power to the starter motor. Refer to Starting and Charging Description and Operation for 
circuit description.
Anti-Theft Alarm Operation
Fuel flap release switch
A feed from fuse 2 in the passenger compartment fusebox is connected on a PS wire to the 
fuel flap release switch. When the switch is operated and the alarm is not armed, the feed 
passes from the switch and is connected on a PR wire to the fuel flap release solenoid.
The feed energises the solenoid, retracting the plunger and opening the fuel flap. The fuel 
flap release solenoid is connected on an RU wire to pin C0664-3 on the BCU. The BCU 
completes the earth path from the solenoid only if the alarm is not armed. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.3
Vehicle horns
The contacts of the horn relay, in the engine compartment fusebox, are connected to the LH 
and RH horns by PG wires. The LH horn is earthed by a B wire connected to earth point 
C0564. The RH horn is earthed by a B wire connected to earth header C0018. Where the 
vehicle horns are used by the anti-theft alarm system, the horn relay coil is connected to the 
BCU, via header C0286, by a PO wire. To operate the horns the BCU earths the PO wire, 
which energises the relay and connects the feed from fuse 16 in the engine compartment 
fusebox to the horns.
Battery Backed-Up Sounder (BBUS)
Where fitted, operation of the BBUS is controlled by the BCU.
The BBUS is armed and disarmed on a PG wire between BCU pin C0661-14 and the BBUS. 
In the armed condition the BBUS monitors the power feed from the passenger compartment 
fusebox and automatically sounds if it is interrupted. To disarm the BBUS the BCU supplies 
a 12 volts power feed on the PG wire. To arm the BBUS, the BCU disconnects the power 
feed.
The BCU sounds the BBUS using a PO wire between BCU pin C0661-3 and the BBUS. In 
addition to sounding the BBUS when the alarm system has been triggered, armed and 
disarmed, the BCU can also sound the BBUS to produce mislock and EKA warnings. The 
BCU normally maintains a 12 volts power feed to the BBUS on the PO wire. To sound the 
BBUS the BCU disconnects the power feed.
Alarm sounder unit
When fitted, and the IDM and the BCU determine that alarm sounder unit operation is 
required, the IDM provides an earth for the applicable relay coil in the passenger 
compartment fusebox. This energises the coil closing the relay contacts.
With the relay contacts closed, a feed from fuse 21 in the passenger compartment fusebox 
passes through the relay contacts and from the fusebox on a PB LHD/RU RHD wire, via 
header C0293 (RHD only), to the alarm sounder unit.
On LHD vehicles, the alarm sounder unit is connected to earth header C0552 on a B wire.
On RHD vehicles, the alarm sounder unit is connected, via header C0288, to earth header 
C0018 on a B wire. 
						

							DESCRIPTION AND OPERATION
4.4DISCOVERY SERIES II
Key in sensor
A feed from fuse 20 in the passenger compartment fusebox is connected on a P wire to 
header C0289 LHD/C0294 RHD. From the header the feed is connected on a P wire to the 
key in sensor.
When the ignition key is inserted into the lock barrel the key in sensor contacts close. The 
feed passes through the sensor and is connected on a WP wire, via header C0293 LHD/
C0289 RHD, to pin C0662-2 on the BCU.
A second connection from the key in sensor is connected on a PU wire, via header C0285 
LHD/C0294 RHD, to pin C0663-9 on the BCU. This connection is used for the BCU to 
activate the switch illumination.
Body Control Unit (BCU)
A feed from fuse 13 in the engine compartment fusebox is connected on a PN wire to provide 
a permanent power supply to the BCU.
A feed from fuse 20 in the passenger compartment fusebox is connected on a P wire, via 
header C0289 LHD/C0294 RHD to pin C0661-19 on the BCU.
A B wire connects BCU pin C0660-11 to earth header C0551.
Transponder coil
A feed from fuse 20 in the passenger compartment fusebox is connected on a GU wire to 
the transponder coil. The transponder coil is connected on an SR wire to pin C0661-18 on 
the BCU.
The transponder coil is connected on a B wire, via header C0286 LHD/C0288 RHD to earth 
header C0018 LHD/C0017 RHD.
Radio Frequency (RF) receiver
The RF receiver is connected on a PS wire to pin C0661-5 on the BCU and on a BN wire to 
pin C0661-6 on the BCU.
Infra-red receiver (Korean vehicles only)
The infra-red receiver is located in the front interior lamp. A feed from fuse 20 in the 
passenger compartment fusebox is connected on a P wire from header C0289, via header 
C0723, to the front interior lamp. The lamp is connected on a B wire, via splice joint A4, to 
earth header C0706.
The front interior lamp is connected on an RP wire to connector interface C1461-2/C0674-
2. From the connector interface the connection continues on a BN wire to pin C0661-6 on 
the BCU. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.5
LH front door lock motor (LHD vehicles only)
The LH front door lock motor switch is connected on a UG wire to pin C0660-5 on the BCU 
and on a US wire to pin C0661-22 on the BCU.
The LH door switch is connected on a PW wire, via header C0287, to pin C0660-17 on the 
BCU.
The LH front door lock motor is connected on a B wire, via header C0288, to earth header 
C0017.
RH front door lock motor (RHD vehicles only)
The RH front door lock motor switch is connected on a UG wire to pin C0660-5 on the BCU 
and on a US wire to pin C0661-22 on the BCU.
The RH door switch is connected on a PW wire, via header C0285, to pin C0660-17 on the 
BCU.
The RH front door lock motor is connected on a B wire to earth header C0018.
RH front door lock motor (LHD vehicles only)
The RH door switch is connected on a PW wire to connector C0733-1/C0464-1 interface. 
From the connector interface, the wire changes to a PLG wire to header C0291 and from 
header C0291 on a PLG wire to pin C0660-4 on the BCU.
The RH door switch is connected on a B wire to earth header C0018.
LH front door lock motor (RHD vehicles only)
The LH door switch is connected on a PW wire to connector C0733-1/C0464-1 interface. 
From the connector interface, the wire changes to a PLG wire to header C0285 and from 
header C0285 on a PLG wire to pin C0660-4 on the BCU.
The LH Door switch is connected on a B wire to earth header C0017.
Tail door lock motor (LHD/RHD Vehicles)
The tail door open switch is connected on a PLG wire to pin C0660-4 on the BCU via header 
C0285. The boot/tail door switch is also connected on a B wire to earth header C0706.
RH rear door lock motor (LHD vehicles only)
The RH rear door switch is connected on a PLG wire to connector C0805-3/C0756-3 
interface. From the connector interface the wire continues on a PLG wire to header C0291 
and from the header to pin C0660-4 on the BCU. The RH rear door switch is connected on 
a B wire to earth header C0552. 
						

							DESCRIPTION AND OPERATION
4.6DISCOVERY SERIES II
RH rear door lock motor (RHD vehicles only)
The RH rear door switch is connected on a PLG wire to pin C0660-4 on the BCU via header 
C0285. The RH rear door switch is also connected on a B wire to earth header C0552.
LH rear door lock motor (LHD vehicles only)
The LH rear door switch is connected on a PLG wire to connector C0805-3/C0753-3 
interface. From the connector interface the wire continues on a PLG wire to header C0291 
and from the header to pin C0660-4 on the BCU. The LH rear door switch is connected on 
a B wire to earth header C0552.
LH rear door lock motor (RHD vehicles only)
The LH rear door switch is connected on a PLG wire to pin C0660-4 on the BCU via header 
C0285. The LH rear door switch is also connected on a B wire to earth header C0552.
Bonnet switch
The bonnet switch is connected on a PO wire from pin C0660-15 to the switch. The bonnet 
switch is connected on a B wire to earth header C0017, via header C0288.
Instrument pack
The instrument pack is connected on a BS wire to BCU pin C0661-20. This connection is 
used for the alarm LED operation.
Diagnostic socket
The BCU provides outputs to and receives inputs from the diagnostic socket on a K wire, via 
header C0285 LHD/C0286 RHD, to BCU pin C0661-4.
Engine Control Module (ECM)
The ECM is connected to BCU pin C0661-10 on a LGS wire.
Ultrasonic modules
The BCU is connected to the front and rear ultrasonic modules from pin C0663-6 on a WB 
wire. The WB wire passes through splice joint A46 and is connected to the front ultrasonic 
module.
A second connection from the BCU, on an SP wire from BCU pin C0663-8, passes through 
splice joint A44/A105 and is connected to the front ultrasonic module. A second SP wire is 
taken from splice joint A44/A105 and is also connected to the front ultrasonic module.
From splice joint A46 a WB wire is connected to the rear ultrasonic module. From splice joint 
A44/A105 two SP wires are connected to the rear ultrasonic module.
A B wire connects the front ultrasonic module to earth header C0707. A B wire connects the 
rear ultrasonic module to earth header C0706. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.7
CENTRAL DOOR LOCKING (CDL)
DESCRIPTION
General
Four methods are available for locking the doors; locking using vehicle key, remote handset 
locking, locking using the CDL switch on the fascia or speed related locking. The anti-theft 
alarm operates in conjunction with the CDL system. Refer to Anti-Theft Alarm - Description 
and Operation in this manual for alarm details.
Two levels of door locking are available; Central Door Locking (CDL) and Superlocking.
CDL
CDL allows the doors to be locked from inside and outside of the vehicle. In the CDL state, 
the doors can be opened from inside the vehicle or unlocked using the vehicle key or the 
remote handset. CDL can be initiated using the vehicle key in the drivers door lock, the 
remote handset or the CDL switch on the fascia.
CDL locking is also used for the optional speed related locking. This feature automatically 
locks all the doors when the vehicle speed exceeds 4 mph (7 km/h). Refer to the Workshop 
Manual Body Control Unit Description and Operation.
Superlocking
Superlocking only allows the doors to be locked from outside the vehicle. When 
superlocked, the doors cannot be opened from inside the vehicle. Superlocking can be 
initiated with two turns of the vehicle key in the driver’s door lock or the remote handset. In 
the superlocked state the remote handset is used to unlock the doors. In the event of the 
remote handset not being available, the vehicle key can be used in the drivers door lock to 
enter an Emergency Key Access (EKA) code which will unlock the doors and disarm the 
anti-theft alarm. Refer to the Workshop Manual Alarm System for EKA and door locking 
Description and Operation.
An inertia switch is located in the engine compartment. In the event of a collision, the inertia 
switch will trip. When the inertia switch is tripped with the ignition on and the alarm disarmed, 
all doors will automatically unlock and locking of the doors will be prevented until the inertia 
switch is reset.
The locking system can be interrogated using TestBook/T4 for diagnostic information. 
						

							DESCRIPTION AND OPERATION
4.8DISCOVERY SERIES II
OPERATION
CDL Supply
Circuit supply
A feed from the battery positive terminal is connected by an R wire to the engine 
compartment fusebox, where it passes to fusible link 3 and fuse 13.
The feed from fusible link 3 is connected on an NR wire to the passenger compartment 
fusebox where it passes through fuses 1, 20 and 21.
From fuse 1 in the passenger compartment fusebox the feed is connected to the contacts of 
the four electronic CDL relays in the passenger compartment fusebox. When the relay 
contacts are open they are connected on a B wire from the passenger compartment fusebox 
to earth header C0017 LHD/ C0018 RHD.
From fuse 20 in the passenger compartment fusebox the feed is connected on a GU wire to 
the passive coil which surrounds the ignition switch.
From fuse 21 in the passenger compartment fusebox the feed is connected on a P wire via 
header C0289 LHD, and a PB wire, header C0292 and a P wire RHD, to Body Control Unit 
(BCU) pin C0661-19.
The feed from fuse 13 is connected on a PN wire to BCU pin C0660-13 and provides a 
permanent battery supply to the BCU. A second feed from fuse 13 is connected on a PN 
wire to the passenger compartment fusebox and supplies power to the electronic CDL relays 
in the fusebox. A third feed from fuse 13 is connected on an NB wire to the inertia switch.
CDL OPERATION
Inertia switch
When the inertia switch contact is closed (switch not tripped) the feed from fuse 13 in the 
engine compartment fusebox passes through the switch and is connected on a WG wire to 
the engine compartment fusebox. The feed passes through the fusebox and is connected 
on an NS wire to the Intelligent Driver Module (IDM) in the passenger compartment fusebox.
Body Control Unit (BCU)
The BCU is connected from pin C0661-1 on an SK wire (serial data bus), via header C0293/
C0292 RHD to the passenger compartment fusebox. The BCU uses the serial data bus to 
the IDM in the passenger compartment fusebox to energise each electronic relay. When 
each relay is energised power is supplied to each door lock motor as applicable. When each 
relay is de-energised it is connected to earth.
The BCU is connected using the serial data bus from pin C0661-1 on an SK wire, via header 
C0293 LHD/C0292 RHD, to the instrument pack pin C0233-16. The instrument pack pin 
C0230-16 is connected on a KG wire via header C0290 (and splice joint A87 on automatic 
vehicles) to the SLABS ECU pin C0504-3. The SLABS ECU supplies a road speed signal to 
the instrument pack. 
						

							DESCRIPTION AND OPERATION
DISCOVERY SERIES II 4.9
The BCU receives the road speed signal from the instrument pack via the serial data bus to 
BCU pin C0661-1. The BCU uses the speed signal to enable the speed related locking when 
the road speed exceeds 4 mph (7 km/h).
The BCU is connected on a B wire from pin C0660-11 to earth header C0551.
The BCU is connected on a US wire from pin C0660-22 to the driver’s door lock motor 
switch. This connection provides an earth signal which informs the BCU that CDL lock using 
the vehicle key has been requested.
The BCU is connected on a UG wire from pin C0660-5 to the driver’s door lock motor switch. 
This connection provides an earth signal which informs the BCU that superlock using the 
vehicle key has been requested. The door lock motor switch is connected on a B wire, via 
header C0288 (LHD only), to earth header C0017 LHD/C0018 RHD.
Transponder coil
The transponder coil receives a supply from fuse 20 in the passenger compartment fusebox 
on a GU wire. The transponder coil is connected on an SR wire to BCU pin C0661-18. When 
applicable the BCU supplies an earth on this wire to energise the passive coil.
The transponder coil is connected on a B wire, via header C0286 LHD/C0288 RHD, to earth 
header C0018 LHD/C0017 RHD.
Radio frequency (RF) receiver
The RF receiver is connected on a PS wire to pin C0661-5 on the BCU. This connection 
provides the power supply to the RF receiver.
A BN wire is connected from BCU pin C0661-6 to the RF receiver. This connection provides 
an RF signal to the BCU when the remote handset is operated.
The RF receiver is connected on a B wire to earth header C0707.
CDL switch
The CDL switch is connected on a KR wire to BCU pin C0660-16. This connection provides 
an earth input to the BCU to signal that the lock has been requested from the CDL switch.
A second connection from the CDL switch on a YK wire to BCU pin C0662-7 provides an 
earth input to the BCU to signal that unlock has been requested from the CDL switch.
The CDL switch is connected on a B wire, via headers C0725 and C0760, to earth header 
C0017 LHD/C0018 RHD.
Diagnostic socket
The BCU is connected on a K wire, via header 0286, from pin C0661-4 to the diagnostic 
socket pin C0040-7.