2002 LAND ROVER DISCOVERY relay

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-37
Input/Output
Input to the cruise control RES switch is 12 volts via the main relay. When the switch is pressed the circuit is completed
by the ECM providing an earth path for the relay via pin 17 of connector C0658 of the ECM.
The cruise control RES switch can fail as follows:
lOpen circuit.
lShort circuit to voltage supply.
lShort circuit to vehicle earth.
lWiring loom fault.
In the event of a cruise control RES switch failure cruise control resume/ suspend operation does not operate.

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-39
With the ECM in a 'Secure' state, it will not function unless an alarm system is fitted to the vehicle. A 'Secure' ECM
cannot be configured into a 'No Code' ECM.
With the ECM in a 'No Code' state, it does not require an alarm system to be fitted to allow the engine to operate. If
the ECM senses that an alarm system is fitted it will not start. A 'No Code' ECM can be configured to a 'Secure' ECM
using TestBook. A 'Secure' ECM can not be configured to a 'No Code' state.
Setting up of the ECM immobilisation configurations can only be performed using TestBook.
If a vehicle stalls immediately after starting it is possible that it has been immobilised. This means either:
lThe ECM was configured as 'No Code' but the ECM is receiving a code at its alarm input pin.
lThe ECM received an incorrect code.
lThe ECM was expecting a security code but did not receive one at its alarm input pin.
Fuel delivery/injection control
The fuel delivery/injection control delivers a precise amount of finely atomised fuel to mix with the air in the
combustion chamber to create a controlled explosion.
To precisely control fuel delivery and control fuel injection, the following input conditions must be met:
lCKP information.
lInjection timing map information.
lFT information.
lECT information.
The ECM monitors the conditions required for optimum combustion of fuel in the cylinder from the various sensors
around the engine and then compares it against stored information. From this calculation the ECM can adjust the
quantity and timing of the fuel being delivered to the cylinder.
The ECM uses CKP information as follows:
lTo calculate engine speed.
lTo determine engine crankshaft position.
Engine speed and crankshaft position allows the ECM to determine fuel injection timing.
The ECM also uses ECT information and FT sensor information to allow optimum fuel delivery and injection control
for all engine coolant and fuel temperatures.
Turbocharger control
Turbocharger control is vital to ensure the turbocharger does not over boost the engine. Within the turbocharger is a
wastegate, which when operated by the turbocharger wastegate modulator will open and close a bypass valve
regulating boost pressure.
The turbocharger wastegate modulator, via the ECM, controls boost pressure under the following conditions:
lAcceleration.
lWide open throttle.
lIdle.
lOverrun.
The turbocharger wastegate modulator receives a battery voltage supply from the main relay. The ECM supplies the
earth path in the form of a pulse width modulation (PWM) signal. This signal allows the turbocharger wastegate
modulator to open and close the wastegate. A proportion of the exhaust gas can bypass the turbocharger through
the wastegate, regulating boost pressure.

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-43
Air Conditioning (A/C)
The ECM controls operation of the A/C compressor and the engine's electric cooling fan in response to requests from
the Automatic Temperature Control (ATC) ECU.
A/C request
When the ATC ECU supplies the ECM with an A/C request, the ECM energises the compressor clutch relay. The
compressor clutch relay is located in the engine compartment fuse box. It is a four pin normally open relay. This means
that the relay must be energised to drive the compressor clutch. During periods of high driver demand such as hard
acceleration or maximum rev/min the ECM will disable the compressor clutch for a short time. This is to reduce the
load on the engine.
The operation of the A/C request is via a switch being connected to earth. Voltage is supplied via pin 9 of connector
C0658 of the ECM, at the point at which the switch is pressed the connection to the earth path is made and the
compressor clutch is engaged.
The ECM provides the earth for the relay windings to allow the compressor clutch relay contacts to close and the
compressor clutch drive to receive battery voltage. The ECM uses a transistor as a switch to generate an open circuit
in the earth path of the relay windings. When the ECM closes down the earth path, the return spring in the relay will
pull the contacts apart to shut down the compressor clutch drive. Fuse 6, located in the engine compartment fuse box,
provides voltage to the compressor clutch relay switching contacts. The relay windings are supplied with battery
voltage from the main relay, also located in the engine compartment fuse box. The earth path for the relay windings
is via pin 29 of the ECM connector C0658. When the relay is energised the output from the switching contacts is
directly to the compressor clutch.
Cooling fan request
The A/C fan request is an input to the ECM from the ATC ECU to request that the engine's electric cooling fan is
activated to provide additional cooling for the A/C condenser.
The cooling fan relay is located in the engine compartment fuse box and is also controlled by the ECM. It is a four pin
normally open relay. This means that the relay must be energised to drive the cooling fan. The cooling fan is used
especially when the engine is operating at excessively high temperatures. It is also used as a part of the ECM backup
strategy if the ECT sensor fails.
The operation of the cooling fan request is via a switch being connected to earth. Voltage is supplied via pin 23 of
connector C0658 of the ECM, at the point at when the switch is pressed the connection to the earth path is made and
the cooling fan is engaged.
The ECM provides the earth for the cooling fan relay windings to allow the relay contacts to close and the cooling fan
motor to receive battery voltage. The ECM uses a transistor as a switch to generate an open circuit in the earth path
of the relay windings. When the ECM closes down the earth path, the return spring in the relay will pull the contacts
apart to shut down the cooling fan motor drive. Input to the A/C cooling fan relay switching contacts is via fuse 4
located in the engine compartment fuse box. The relay windings are supplied with battery voltage from the main relay,
also located in the engine compartment fuse box. The earth path for the relay windings is via pin 4 of the ECM
connector C0658. When the relay is energised the output from the switching contacts is directly to the cooling fan
motor.

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-3
Engine management component
location - Engine compartment
1Mass air flow/ inlet air temperature sensor
2Fuel injectors
3High tension leads/spark plugs
4Fuel pump relay
5ATC compressor clutch relay/ cooling fan relay
6Throttle position sensor
7Heated oxygen sensor
8Idle air control valve
9Ignition coils
10Engine coolant temperature sensor
11Crankshaft speed and position sensor
12Knock sensor
13Camshaft position sensor

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-5
1Engine control module
2Crankshaft speed and position sensor
3Camshaft position sensor
4Engine coolant temperature sensor
5Mass air flow/ inlet air temperature sensor
6Throttle position sensor
7Heated oxygen sensors
8Fuel injectors
9Idle air control valve
10Fuel pump relay
11EVAP canister
12EVAP canister vent valve
13EVAP canister purge valve
14Fuel tank pressure sensor
15Ignition coils
16Knock sensor
17Spark plugs
18High/ Low ratio switch
19Malfunction indication lamp
20Diagnostic connector
21Air temperature control clutch relay
22Air temperature control cooling fan relay
23ATC ECU
24CAN link to EAT
25SLABS ECU
26BCU
27Instrument cluster
28Thermostat monitoring sensor (where fitted)

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-7
The ECM controls the following outputs:
lFuel injectors (1 per cylinder).
lIgnition coils/ high tension leads/ spark plugs.
lFuel pump relay.
lIdle air control valve.
lHeated oxygen sensors.
lEVAP canister purge valve.
lEVAP canister vent solenoid (CVS) valve (where fitted).
lMalfunction Indicator Lamp (MIL)/ service engine soon lamp (where fitted).
lHill descent control (via SLABS interface).
lEVAP system fuel leak detection pump (where fitted)
lSecondary air injection pump (where fitted)
The ECM also interfaces with the following:
lDiagnostics via diagnostic connector with TestBook.
lController Area Network (CAN) link to EAT ECU.
lAir conditioning system.
lSelf Levelling & Anti-lock Braking System (SLABS) ECU.
lImmobilisation system via the body control unit (BCU).
lInstrument cluster.
lCruise control ECU
lActive Cornering Enhancement (ACE) ECU
Engine Control Module (ECM)
The engine control module (ECM) is located on the RH side A post below the face panel inside the vehicle. It has a
cast aluminium case and is mounted on a bracket. The ECM has 5 independent connectors totalling 134 pins.
The ECM is available in 4 variants:
lNAS.
lNAS low emission vehicles.
lUK/ Europe/ Japan/ Australia.
lROW/ Gulf.
The ECM uses a 'flash' electronic erasable programmable read only memory (EEPROM). This enables the ECM to
be externally configured, to ensure that the ECM can be updated with any new information, this also allows the ECM
to be configured with market specific data. TestBook must be used to configure replacement ECM's. The ECM can
be reconfigured up to 16 times to meet changing specifications and legislation.
The ECM memorises the positions of the crankshaft and the camshaft when the engine has stopped via the CKP and
CMP sensors. This allows immediate sequential fuel injection and ignition timing during cranking. This information is
lost if battery voltage is too low (i.e. flat battery). So the facility will be disabled for the first engine start.

ENGINE MANAGEMENT SYSTEM - V8
18-2-8 DESCRIPTION AND OPERATION
Input/Output
The ECM has various sensors fitted to the engine to allow it to monitor engine condition. The ECM processes these
signals and decides what actions to carry out to maintain optimum engine operation by comparing the information
from these signals to mapped data within its memory.
Connector 1 (C0634): This connector contains 9 pins and is used primarily for ECM power input and earth. The ECM
requires a permanent battery supply, if this permanent feed is lost i.e. the battery discharges or is disconnected the
ECM will lose its adapted values and its Diagnostic Trouble Codes (DTC). These adapted values are a vital part of
the engine management's rolling adaptive strategy. Without an adaptive strategy, driveability, performance, emission
control, and fuel consumption are adversely affected. The ECM can be damaged by high voltage inputs, so care must
be taken when removing and replacing the ECM.
Pin out details connector C0634
Connector 2 (C0635): This connector contains 24 pins and is primarily used for Heated Oxygen Sensors (HO
2S)
control and earth. The HO
2S sensors require a heater circuit to assist in heating the tip of the sensors to enable closed
loop fuelling to be implemented quickly after cold starting.
Pin out details connector C0635
Pin No. Function Signal type Reading
1 Ignition position II Input 12 V
2 Not used - -
3 Not used - -
4 Chassis earth Earth 0V
5 Fuel injectors earth Earth 0V
6 Power stage earth Earth 0V
7 Permanent battery supply Input battery supply 12V
8 Switched relay positive Input switched 0-12V
9 Not used - -
Pin No. Function Signal type Reading
1HO
2S heater RH bank - downstream Output PWM 12-0V
2 Not used - -
3 Not used - -
4 Not used - -
5 Thermostat monitoring sensor Earth 0V
6 Not used - -
7HO
2S heater LH bank - downstream Output PWM 12-0V
8HO
2S sensor RH bank - downstream Earth/ Signal 0V
9HO
2S sensor LH bank - upstream Earth/ Signal 0V
10 HO
2S sensor RH bank - upstream Earth/ Signal 0V
11 HO
2S sensor LH bank - downstream Earth/ Signal 0V
12 Not used - -
13 HO
2S heater RH bank - upstream Output PWM 12-0V
14 HO
2S sensor RH bank - downstream Input/ Signal Analogue 0-5V
15 HO
2S sensor LH bank - upstream Input/ Signal Analogue 0-5V
16 HO
2S sensor RH bank - upstream Input/ Signal Analogue 0-5V
17 HO
2S sensor LH bank - downstream Input/ Signal Analogue 0-5V
18 Fuel pump relay Output Switch to earth
19 HO
2S heater LH bank - upstream Output PWM 12-0V
20 Not used - -
21 Thermostat monitoring sensor Signal Analogue 0-5V
22 Not used - -
23 Main relay Output Switch to earth
24 EVAP system leak detection pump motor (NAS
vehicles with positive pressure type, EVAP system
leak detection capability only)Output Switch to earth

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-9
Connector 3 (C0636): This connector contains 52 pins and is used for most sensor and actuator inputs and outputs.
Sensor and actuator control is vital to ensure that the ECM maintains adaptive strategy
Pin out details connector C0636
Pin No. Function Signal type Reading
1 Injector cylinder number 2 Output Switch to earth
2 Injector cylinder number 5 Output Switch to earth
3 Purge valve Output, signal PWM 12-0V
4 SAI vacuum solenoid valve (NAS vehicles from
2000MY only)Output Switch to earth
5 Not used - -
6 Fuel tank pressure sensor (NAS vehicles with
vacuum type, EVAP system leak detection
only)Earth 0V
7 MAF sensor 5V supply Output, reference 5V
8 Not used - -
9 MAF sensor earth Earth 0V
10 TP sensor 5V supply Output, reference 5V
11 Not used - -
12 Not used - -
13 Not used - -
14 Injector cylinder number 7 Output Switch to earth
15 Injector cylinder number 6 Output Switch to earth
16 SAI pump relay (NAS vehicles from 2000MY
only)Output Switch to earth
17 CMP sensor Earth 0V
18 Low range switch (manual transmission only) Input, signal Active low
19 Not used - -
20 CMP signal Input, signal Digital switch 0-12V
21 ECT sensor Earth 0V
22 Coolant temperature signal Input, signal Analogue 0-5V
23 MAF sensor signal Input, signal Analogue 0-5V
24 TP sensor signal Input, signal Analogue 0-5V
25 TP sensor earth Earth 0V
26 Not used - -
27 Injector cylinder number 3 Output Switch to earth
28 Injector cylinder number 8 Output Switch to earth
29 Hill decent control output Output, signal PWM 0-12V
30 EVAP canister vent solenoid (CVS) valve (NAS
vehicles with vacuum type, EVAP system leak
detection only)Output Switch to earth
30 Leak detection pump solenoid (NAS vehicles
with positive pressure type, EVAP system leak
detection only)Output Switch to earth
31 A/C condenser fan Output Switch to earth
32 CKP sensor signal Input, signal Analogue, 0-300V peak
33 Not used - -
34 IAT sensor signal Input, signal Analogue 0-5V
35 KS, RH bank earth Earth 0V
36 KS, RH bank signal Input, signal Analogue
37 Not used - -
38 Not used - -
39 Not used - -
40 Injector cylinder number 4 Output Switch to earth
41 Injector cylinder number 1 Output Switch to earth