Land Rover Freelander 2003my Electrical Library Rover Manual

							DESCRIPTION AND OPERATION
4.66FREELANDER 03MY
ANTI-LOCK BRAKING SYSTEM (ABS)
DESCRIPTION
General
The ABS is a full time, four channel system that gives individual speed control to all four 
wheels to provide the vehicle with anti-lock braking (ABS), Electronic Traction Control 
(ETC), and Hill Descent Control (HDC). The systems are controlled by the ABS ECU, which 
is mounted on the rear of the ABS modulator. The ABS ECU also controls the front to rear 
brake balance by Electronic Braking force Distribution (EBD). This maximises vehicle 
stability under braking.
For a detailed description of ABS, ETC HDC, and EBD, refer to the  Brakes  section of the 
System Description and Operation Workshop manual.
The ABS modulator uses the CAN-BUS to communicate with other ECUs to enable it to 
control braking more efficiently. For more information on the CAN-BUS, refer to the  
Communication Databuses  section of the System Description and Operation Workshop 
manual.
OPERATION
General
Feed from the positive battery terminal (C0192) is supplied to fusible link 1, fusible link 3, 
fusible link 8, and fusible 11 (C0632) on an R wire. All are located in the engine compartment 
fuse box.
Fusible link 8 (C0574) and fusible link 11 (C0570) provide constant battery feeds to the ABS 
modulator (C0501) on NK and NR wires respectively. The ABS modulator (C0501) is 
earthed on a pair of B wires.
Fusible link 1 is connected in series with fusible link 2, which is also located in the engine 
compartment fuse box. Fusible link 2 (C0571) provides a feed to the ignition switch (C0028) 
on an NR wire. Fusible link 3 (C0571) also provides a feed to the ignition switch (C0028) on 
an N wire.
When the ignition switch is turned to the ignition position, current flows across the switch 
(C0028) to fuse 2 of the passenger compartment fuse box (C0588) on an NW wire. When in 
the ignition position, the ignition switch (C0028) also provides a feed to fuse 7 and fuse 35 
of the passenger compartment fuse box on a G wire. 
						

							DESCRIPTION AND OPERATION
FREELANDER 03MY 4.67
Fuse 2 of the passenger compartment fuse box (C0580) provides an ignition feed to the 
brake pedal switch (C0075) and the HDC relay (C0574) on G wires. Fuse 35 (C0580) 
provides an ignition feed to the hill descent switch (C0365 on manual transmission vehicles, 
C0878 on automatic transmission vehicles), and the hill descent relay (C0571) on W wires. 
Fuse 7 (C0582) provides an ignition feed to the ABS ECU (C0501) on a W wire.
Wheel Speed Sensors
The ABS ECU (C0501) supplies a feed to all four wheel speed sensors as follows:
zTo the LH front wheel speed sensor (C0516) on an R wire.
zTo the RH front wheel speed sensor (C0517) on a Y wire.
zTo the LH rear wheel speed sensor (C0502) on a G wire.
zTo the RH rear wheel speed sensor (C0503) on a W wire.
The wheel speed sensors provide the ABS ECU with a square wave form signal. By 
measuring the frequency of the wave form, the ABS ECU can calculate the speed of the road 
wheel. The sensors provide the ABS ECU (C0501) with wheel speed signals as follows:
zFrom the LH front wheel speed sensor (C0516) on an RB wire.
zFrom the RH front wheel speed sensor (C0517) on a YB wire.
zFrom the LH rear wheel speed sensor (C0502) on a GB wire.
zFrom the RH rear wheel speed sensor (C0503) on a WB wire.
If the ABS ECU detects wheel deceleration is too great, it will initiate the ABS. If the ABS 
ECU detects that wheel speed is greater than vehicle speed, it will initiate ETC. If HDC is 
operational, the ABS ECU will control vehicle speed at 7 mph (11 km/h) by applying the 
brakes where necessary. For more information on ABS, ETC, and HDC, refer to the  Brakes  
section of the System Description and Operation Workshop manual.
ABS ECU
Td4 – Manual Transmission
The ABS ECU (C0501) provides a road wheel speed signal to the Engine Control Module 
(ECM) (C0331) via the CAN BUS on YN (low) and YB (high) wires.
Td4 – Automatic Transmission
The ABS ECU (C0501) provides a road wheel speed signal to the Electronic Automatic 
Transmission Electronic Control Unit (EAT ECU) (C0932) via the CAN BUS on YN (low) and 
YB (high) wires.
K1.8
The ABS ECU (C0501) provides a road wheel speed signal to the Engine Control Module 
(ECM) (C0913) via the CAN BUS on YN (low) and YB (high) wires. 
						

							DESCRIPTION AND OPERATION
4.68FREELANDER 03MY
KV6
The ABS ECU (C0501) provides a road wheel speed signal to the EAT ECU (C0932) via the 
CAN BUS on YN (low) and YB (high) wires. This information is relayed to the ECM (C0371) 
via the CAN BUS on YN (low) and YB (high) wires.
For more information on the CAN BUS, refer to the  Communication Databuses  section 
of the System Description and Operation Workshop manual.
The ABS ECU (C0501) also provides a pulsed road speed signal to the CCU (C0428) on a 
WO wire.
Brake Pedal Switch
The brake pedal switch is a double contact mechanical switch, mounted at the top of the 
brake pedal adjacent the brake pedal sensor. The switch (C0075) is provided an ignition 
feed from fuse 2 of the passenger compartment fuse box (C0580) on a G wire. When the 
brake pedal is at rest, the switch (C0075) provides a feed to the ABS ECU (C0501) on a GR 
wire. When the brake pedal is pressed, the switch (C0075) informs the ABS ECU (C0501) 
by providing a feed on a GP wire.
When the brake pedal is pressed, the switch (C0075) also provides a feed to the following 
on GP wires:
zThe LH brake lamp (C0121).
zThe RH brake lamp (C0125).
zThe Centre High Mounted Stop Lamp (CHMSL) (C0613).
For more information on brake lamp operation, refer to the  Brake and Reverse Lamps  
section of this manual.
 
+  BRAKE AND REVERSE LAMPS. 
Accelerometer
The accelerometer is mounted beneath the centre console adjacent the handbrake, and 
provides the ABS ECU additional information regarding vehicle motion. The ABS ECU 
(C0501) provides a feed to the accelerometer (C1220) on a Y wire. The sensor (C1220) 
returns a vehicle acceleration/deceleration signal to the ABS ECU (C0501) on an R wire.
The accelerometer (C1220) is provided an earth path via the ABS ECU (C0501) on a U wire.  
						

							DESCRIPTION AND OPERATION
FREELANDER 03MY 4.69
Brake Fluid Level Switch
The ABS ECU (C0501) provides a feed to the brake fluid level switch (C0026) on a BW wire. 
The switch is closed when the correct amount of brake fluid is present in the brake fluid 
reservoir. The switch (C0026) is earthed on a B wire. If the brake fluid level drops below the 
recommended level, the switch contacts open. When the ABS ECU registers the switch 
opening, it informs the instrument pack to illuminate the brake fluid warning lamp via the 
CAN-BUS. 
For more information on warning lamp operation, refer to the  Instruments  section of this 
manual.
 
+  INSTRUMENTS. 
Hill Descent Control (HDC)
HDC Switch (Manual Transmission)
The HDC switch (C0365) is mounted on the gear lever, and informs the ABS ECU (C0501) 
when HDC has been selected. When HDC is selected, the switch contacts close, and a feed 
is provided to the ABS ECU (C0501) on a PS wire. When the ABS ECU receives this feed, 
it energises the HDC relay.
HDC Switch (Automatic Transmission)
The HDC switch (C0878) is mounted on the centre console, and informs the ABS ECU 
(C0501) when HDC has been selected. When HDC is selected, the switch contacts close, 
and a feed is provided to the ABS ECU (C0501) on a PS wire. When the ABS ECU receives 
this feed, it energises the HDC relay.
NOTE: The ABS ECU will only initiate HDC if either 1st or reverse gear are selected, and 
brake temperature doesnt exceed 400 
°C (752 °F).
1st Gear Switch (Manual Transmission)
The 1st gear switch (C0618) is mounted in the gearbox, and informs the ABS ECU (C0501) 
when 1st gear has been selected. The Instrument pack (C0230) provides a feed to the 
switch (C0618) on an RW wire (RW then GB on K1.8 vehicles). When 1st gear is selected, 
the instrument pack (C0230) informs the ABS ECU (C0501) via the CAN BUS on YN (low) 
and YB (high) wires. The switch (C0618) is earthed on a B wire. 
						

							DESCRIPTION AND OPERATION
4.70FREELANDER 03MY
HDC Relay
The HDC relay (C0575) is located in the engine compartment fuse box, and is controlled by 
the ABS ECU (C0501) on a BR wire. When energised, the HDC relay (C0570) provides a 
feed to the following on GP wires:
zThe ABS ECU (C0501).
zThe LH brake lamp (C0121).
zThe RH brake lamp (C0125).
zThe CHMSL (C0613).
Diagnostic Socket
The diagnostic socket (C0040) is connected to the ABS ECU (C0501) by a K wire, enabling 
the ABS ECU to be interrogated by TestBook or T4. 
						

							DESCRIPTION AND OPERATION
FREELANDER 03MY 4.71
SUPPLEMENTARY RESTRAINT SYSTEM (SRS)
DESCRIPTION
General
The Supplementary Restraint System (SRS) is designed to work in conjunction with the 
vehicle seat belts. The main components of the system are:
zDriver Airbag – Mounted in the steering wheel to provide added protection for the driver 
during a frontal impact.
zPassenger airbag – Mounted in the fascia to provide added protection for the front seat 
passenger during a frontal impact.
zSeat Belt Pre-tensioners – Mounted on the inner edge of both front seats within the 
seat belt anchorage, to provide added protection during a front impact.
zAirbag Diagnostic Control Unit (DCU) – Mounted beneath the centre console, and used 
detect crash conditions and control the SRS system.
zSRS LED – Mounted in the instrument pack, the LED acts as an indicator of system 
status.
NOTE: The airbag DCU illuminates the SRS LED for 5 seconds when the ignition switch is 
turned to the ignition position to inform the driver the SRS LED is functioning correctly.
WARNING: Before starting work on the SRS system, refer to the safety precautions 
contained within the Workshop manual.
For a detailed description of the SRS system and safety precautions to carry out before 
starting work, refer to the System Description and Operation Workshop manual.
OPERATION
General
Feed from the positive battery terminal (C0192) is supplied to fusible link 3 of the engine 
compartment fuse box (C0632) on an R wire. Fusible link 3 (C0571) is connected to the 
ignition switch (C0028) by an N wire. When the ignition switch is turned to the ignition 
position, current flows across the switch (C0028) to fuse 8, and fuse 36 of the passenger 
compartment fuse box (C0588) on a G wire.
Fuse 36 (C0580) provides an ignition feed to the airbag DCU (C0256) on a G wire. The DCU 
(C0256) is earthed on a B wire. Fuse 8 (C0589) provides an ignition feed to the SRS LED 
(C0233) on a G wire. 
						

							DESCRIPTION AND OPERATION
4.72FREELANDER 03MY
Driver Airbag
The airbag DCU (C0256) controls the feed to the driver airbag (C0545) via the rotary coupler 
(C0374) on a Y wire. The airbag DCU (C0256) controls the earth path for the driver airbag 
(C0545) via the rotary coupler (C0374) on an R wire.
Passenger Airbag
The airbag DCU (C0256) controls the feed to the passenger airbag (C0433) on a W wire. 
The earth path for the passenger airbag (C0433) is controlled by the airbag DCU (C0256) 
on a U wire.
Seat Belt Pre-tensioners
RH
The airbag DCU (C0256) controls the feed to the RH pre-tensioner (C0254) on an N wire. 
The earth path for the RH pre-tensioner (C0254) is controlled by the airbag DCU (C0256) 
on an NR wire.
LH
The airbag DCU (C0256) controls the feed to the LH pre-tensioner (C0252) on an O wire. 
The earth path for the LH pre-tensioner (C0252) is controlled by the airbag DCU (C0256) on 
an OU wire.
SRS LED
Fuse 8 of the passenger compartment fuse box (C0589) provides an ignition feed to the SRS 
LED (C0233) on a G wire. To illuminate the LED (C0233), an earth path is provided on a YR 
wire via the airbag DCU (C0256). To extinguish the LED, the airbag DCU withdraws the 
earth path.
Diagnostic Socket
The SRS system can be interrogated using TestBook or T4 via the diagnostic socket. The 
diagnostic socket (C0040) is connected to the airbag DCU (C0256) by a K wire. 
						

							DESCRIPTION AND OPERATION
FREELANDER 03MY 4.73
AIR CONDITIONING (A/C) – Td4
DESCRIPTION
General
The air conditioning (A/C) system will only operate when the engine is running. The A/C 
system is switched on and off by pressing the switch mounted on the centre console. When 
the switch is pressed, an LED mounted within the switch illuminates to inform the driver the 
system is operational. For more information on LED operation, refer to the  Interior 
Illumination  section of this manual.
 
+  INTERIOR ILLUMINATION. 
The position of the rotary heater control determines the amount of warm air from the heater 
matrix blended with cool air from the A/C evaporator, and hence the temperature of the air 
output from the heater ducts. 
NOTE: The blower switch must be in at least position 1 for the A/C system to operate.
The A/C system is automatically switched on when either the screen or screen/feet positions 
are selected via the rotary distribution control knob.
NOTE: The A/C LED will not illuminate under these conditions.
For more information on heater operation, refer to the  Heater Blower section of this 
manual.
 
+  HEATER BLOWER. 
OPERATION
General
Feed from the positive battery terminal (C0192) is supplied to fusible link 5, fusible link 1 and 
the main relay (C0632) on an R wire. All are located within the engine compartment fuse 
box. 
The earth path for the main relay coil (C0576) is controlled by the Engine Control Module 
(ECM) (C0603) on a WK wire. The energised main relay provides a feed to fuse 4, which is 
also located in the engine compartment fuse box. For more details on main relay operation, 
refer to the  Engine Management Systems – EDC  section of the System Description and 
Operation Workshop manual. 
						

							DESCRIPTION AND OPERATION
4.74FREELANDER 03MY
Fusible link 1 is connected in series with fusible link 2, fuse 8, and fuse 9 which are also 
located in the engine compartment fuse box. Fuse 8 (C0576) provides a constant battery 
feed to the heater blower relay (C0153) on a GN then GW wire. Fuse 9 provides a constant 
battery feed to the compressor clutch relay, which is also located in the engine compartment 
fuse box.
Fusible link 2 (C0571) is connected to the ignition switch (C0028) by an NR wire. When the 
ignition switch is turned to the ignition position, current flows across the switch (C0028) to 
fuse 4 of the passenger compartment fuse box (C0588) on an SU wire. Fuse 4 (C0586) 
provides an ignition feed to the following on G then LGS wires:
zThe blower motor switch (C0058).
zThe fresh/recirculated air switch (C0750).
zThe fresh/recirculated air motor (C0006).
A/C Master Switch
When the blower switch (C0058) is turned to position 1 or higher, it provides a feed to the A/
C master switch (C0275) and the A/C microswitch (C2575) on SW then B wires. If A/C is 
requested, the switch (C0275) provides a feed to the instrument pack (C0233) via the 
microswitch (C2575) on a B then SK wire. When the instrument pack receives an A/C 
request from the switch, it informs the ECM (C0913 K Series vehicles, C0371 on KV6 
vehicles) via the CAN BUS on YN (Low) and YB (High) wires. The A/C master switch is 
mounted on the centre console, and is earthed (C0275) on a B wire.
For more information on the CAN BUS, refer to the  Communication Databuses  section 
of the System Description and Operation Workshop manual.
A/C Microswitch
The A/C microswitch (C2575) is mounted on the rear of the heater distribution control knob, 
and switches the A/C on automatically when the screen or feet/screen position is selected. 
In this instance, the switch contacts close, allowing the blower motor switch (C0058) to 
provide a feed to the instrument pack (C0233) on an SW then SK wire, by-passing the A/C 
master switch.
Compressor
When the ECM (C0331) receives an A/C request signal via the CAN BUS, it will energise 
the A/C compressor clutch relay by providing an earth path for the relay coil (C0576) on a 
UB wire. A feed from fuse 9 of the engine compartment fuse box is now able to flow across 
the energised relay (C0575) to the compressor clutch (C0127) on an R wire. 
						

							DESCRIPTION AND OPERATION
FREELANDER 03MY 4.75
Instrument Pack
The instrument pack (C0230) acts as a gateway, relaying CAN messages to and from 
different components throughout the vehicle as follows:
Pressure Sensor
The pressure sensor is located in the high pressure A/C line adjacent the compressor, and 
replaces the more traditional trinary pressure switch. The instrument pack (C0230) provides 
a 5 V reference voltage to the pressure sensor (C1257) on a UO wire. The pressure sensor 
(C1257) is provided an earth path via the instrument pack (C0230) on a PB wire.
The pressure sensor (C1257) provides the instrument pack (C0230) a signal feed on a UG 
wire. The value of this signal feed is dependent upon the pressure within the A/C system. 
This signal is relayed by the instrument pack (C0230) to the ECM (C0331) via the CAN-BUS 
on YB (High) and YN (Low) wires. The ECM uses this signal to determine the pressure within 
the A/C system, enabling it to carry out the following tasks:
zTo provide a safety cut-out function if the pressure within the A/C system goes either 
too high or too low.
zTo control the speed of the cooling and condenser fans via the cooling fan ECU.
zTo help control engine idle speed.
Evaporator Temperature Sensor
The evaporator temperature sensor is used to ensure the evaporator doesnt freeze. The 
instrument pack (C0230) provides a feed to the evaporator temperature sensor (C0417) on 
a GO wire. The sensor (C0417) is earthed on a B wire. The instrument pack relays the 
temperature reading to the ECM (C0331) via the CAN BUS on YB (High) and YN (Low) 
wires. 
NOTE: The ECM also uses the evaporator temperature sensor signal in conjunction with the 
pressure sensor signal to help control engine idle speed.
For more information on CAN messages, refer to the  Communication Databuses section 
of the System Description and Operation Workshop manual.
Cooling Fan Control Unit
Fusible link 5 of the engine compartment fuse box (C0573) provides a constant battery feed 
to the cooling fan control unit (C0208) on an NG wire. Fuse 4 of the engine compartment 
fuse box (C0575) provides a feed to the cooling control unit (C1680) on an NK wire when 
the main relay is energised (see above). The cooling control unit (C0208) is earthed on a B 
wire.
To control cooling fan and condenser fan speed, the ECM (C0331) provides the cooling fan 
control unit (C1680) a Pulse Width Modulated (PWM) signal on a UW wire. The frequency 
of the pulses supplied by the ECM determines the speed the cooling fan control unit will drive 
the cooling fan and condenser fan motors.