1999 LAND ROVER DISCOVERY cooling

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 sensor15Ignition 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 18-2-19
Input/Output
The electrical input and output to and from the ECT sensor are reference voltage and sensor earth. The ECM provides
the ECT sensor with a 5 volt reference via pin 22 of connector C0636 of the ECM, and earth via pin 21 of connector
C0636 of the ECM. The normal operating parameters of the ECT sensor are as follows
Should the sensor fail the ECM has a back up strategy that uses a changing default value during warm up based on
the signal from the inlet air temperature sensor. When the strategy default value reaches 60 °C (140 °F), the ECM
implements a fixed default value of 85 °C (185 °F). It will also illuminate the MIL.
The ECT sensor can fail the following ways or supply incorrect signal:
lSensor open circuit.
lShort circuit to vehicle supply.
lShort circuit to earth.
lIncorrect mechanical fitting.
lSignal fixed above 40 °C (140 °F) will not be detected.
lSignal fixed below 40 °C (140 °F) will be detected.
In the event of an ECT sensor signal failure any of the following symptoms may be observed:
lDifficult cold start.
lDifficult hot start.
lDriveability concern.
lMIL illuminated.
lInstrument cluster temperature warning lamp illuminated.
lTemperature gauge reads excessively hot.
lTemperature gauge reads excessively cold.
lCooling fan will not run.
M124704A
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145-50-35-20-5102540557085100115130

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-27
There are two types of IAT sensor diagnostic checks:
lThe IAT sensor signal is less than the minimum threshold – the engine has to have been running for longer than
180 seconds, and idle speed control must have been operational for longer than 10 seconds. No fuel cut off is
active. The IAT sensor signal must be less than -35°C (-31°F) for longer than 200 ms.
lThe IAT sensor signal is greater than the maximum threshold – the ECM has to be powered up (engine does not
need to be running), and the signal must be greater than 140°C (284°F) for longer than 200 ms.
If the IAT sensor fails the following fault codes will be produced and can be retrieved by TestBook:
Air intake duct – Gulf models from 2000MY
1Heat reflective insulation2Supplementary air intake duct
The density of the intake air is partly dependent on altitude and temperature. Hot air has a lower density than cold air;
consequently in hot climates, the low air density can result in low power due to low volumetric efficiency.
In order to improve engine performance, Gulf specification models from 2000MY have a secondary air intake duct
which is located under the front left inner wing of the vehicle. Cooler air from the side of the vehicle is routed through
the duct to the air cleaner, where it combines with air entering via the front grille.
In addition to the secondary air duct, the vehicles are fitted with a larger front grille and have larger cooling and
condenser fans.
The MAF/IAT sensor, air cleaner and air cleaner duct are encased in insulation bags to help keep the intake air cool
and so increase the mass of air entering the engine intake manifold.
The air cleaner includes a cyclone filter and also a dump valve in the bottom of the unit. Sand and dust particles which
are carried into the air cleaner with the air flow are automatically expunged via the dump valve.
P code J2012 description Land Rover description
P0112 Intake air temperature circuit low input Intake air temperature signal less than minimum
threshold, after time for exhaust to warm up
P0113 Intake air temperature circuit high input Intake air temperature signal greater than maximum
threshold
M180452
1
2

ENGINE MANAGEMENT SYSTEM - V8
18-2-48 DESCRIPTION AND OPERATION
Cooling fan relay
The cooling fan relay is located in the engine compartment fuse box. It is a four pin normally open relay. The relay
must be energised to drive the cooling fan.
The cooling fan is used to cool both the condenser in which the ATC refrigerant is held and the radiator. This 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 fails.
Input/Output
The ECM provides the earth for the relay coils 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 opens 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 cooling fan relay switching contacts is via fuse 5 located in the engine compartment fuse box. The relay
coils are supplied with battery voltage from the main relay, also located in the engine compartment fuse box. The earth
path for the relay coils is via pin 31 of the ECM connector C0636. When the relay is energised the output from the
switching contacts is directly to the cooling fan motor.
The cooling fan relay can fail in the following ways:
lRelay open circuit.
lShort circuit to vehicle battery supply.
lShort circuit to vehicle earth.
lBroken return spring.
In the event of a cooling fan relay failure, the cooling fan does not work.

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-51
Conditions
The ECM calculates ignition timing using input from the following:
lCKP sensor.
lKnock sensors (KS).
lMAF sensor.
lTP sensor (idle only).
lECT sensor.
Function
At engine start up, the ECM sets ignition timing dependent on ECT information and starting rev/min from the CKP. As
the running characteristics of the engine change, the ignition timing changes. The ECM compares the CKP signal to
stored values in its memory, and if necessary advances or retards the spark via the ignition coils.
Ignition timing is used by the ECM for knock control.
Knock control
The ECM uses active knock control to prevent possible engine damage due to pre-ignition. This is achieved by
converting engine block noise into a suitable electrical signal that can be processed by the ECM. A major contributing
factor to engine 'knock' is fuel quality, the ECM can function satisfactorily on 91 RON fuel as well as the 95 RON fuel
that it is calibrated for.
Conditions
The ECM knock control system operates as follows:
lHot running engine.
l91 or 95 RON fuel.
Function
The ECM knock control uses two sensors located one between the centre two cylinders of each bank. The knock
sensors consist of piezo ceramic crystals that oscillate to create a voltage signal. During pre-ignition, the frequency
of crystal oscillation increases which alters the signal output to the ECM.
If the knock sensors detect pre-ignition in any of the cylinders, the ECM retards the ignition timing by 3° for that
particular cylinder. If this action stops the engine knock, the ignition timing is restored to its previous figure in
increments of 0.75°. If this action does not stop engine knock then the ECM retards the ignition timing a further 3° up
to a maximum of -15° and then restores it by 0.75° and so on until the engine knock is eliminated.
The ECM also counteracts engine knock at high intake air temperatures by retarding the ignition as above. The ECM
uses the IAT signal to determine air temperature.
Idle speed control
The ECM regulates the engine speed at idling. The ECM uses the idle air control valve (IACV) to compensate for the
idle speed drop that occurs when the engine is placed under greater load than usual. When the throttle is in the rest
position i.e. it has not been pressed, the majority of intake air that the engine consumes comes from the idle air control
valve.
IACV control idle speed
Conditions in which the ECM operates the IACV control idle speed is as follows:
lIf any automatic transmission gears other than P or N are selected.
lIf air conditioning is switched on.
lIf cooling fans are switched on.
lAny electrical loads activated by the driver.
Function
The idle air control valve utilises two coils that use opposing pulse width modulated (PWM) signals to control the
position of a rotary valve. If one of the circuits that supplies the PWM signal fails, the ECM closes down the remaining
signal preventing the idle air control valve from working at its maximum/ minimum setting. If this should occur, the idle
air control valve assumes a default idle position at which the engine idle speed is raised to 1200 rev/min with no load
placed on the engine.

ENGINE MANAGEMENT SYSTEM - V8
18-2-82 REPAIRS
Sensor - engine coolant temperature
(ECT)
$% 18.30.10
Remove
1.Release turnbuckles and remove battery cover.
2.Disconnect battery earth lead.
3.Remove auxiliary drive belt.

+ CHARGING AND STARTING,
REPAIRS, Belt - auxiliary drive.
4.Remove 2 bolts securing alternator, release
alternator from support bracket and position
aside. 5.Disconnect multiplug from ECT sensor.
6.Remove sensor from inlet manifold and discard
sealing washer.
Refit
1.Clean sealant from threads in manifold.
2.Apply sealant, Part No. STC 50552 to sensor
threads.
3.Fit new sealing washer to ECT sensor and
tighten sensor to 10 Nm (7 lbf.ft).
4.Connect multiplug to ECT sensor.
5.Position alternator, fit bolts and tighten to 45
Nm (33 lbf.ft).
6.Fit auxiliary drive belt.

+ CHARGING AND STARTING,
REPAIRS, Belt - auxiliary drive.
7.Top up cooling system.
8.Connect battery earth lead.
9.Fit battery cover and secure with fixings.

ENGINE MANAGEMENT SYSTEM - V8
18-2-84 REPAIRS
Sensor - radiator temperature
$% 18.30.20
Remove
1.Disconnect battery earth lead.
2.Position container to collect coolant spillage.
3.Disconnect multiplug from sensor.
4.Remove sensor and discard sealing washer.
Refit
1.Fit new sealing washer to sensor.
2.Fit and tighten sensor.
3.Connect multiplug to sensor.
4.Refill cooling system.
5.Connect battery earth lead.
Sensor - camshaft position (CMP)
$% 18.30.24
Remove
1.Release fixings and remove battery cover.
2.Disconnect battery earth lead.
3.Raise front of vehicle.
WARNING: Do not work on or under a
vehicle supported only by a jack. Always
support the vehicle on safety stands.
4.Release fixings and remove underbelly panel.
5.Remove engine oil filter.

+ ENGINE - V8, REPAIRS, Filter - oil.
6.Disconnect engine harness from CMP sensor
and release CMP sensor multiplug from
bracket.
7.Remove bolt from clamp securing CMP sensor
to timing gear cover.
8.Remove clamp and CMP sensor. Discard 'O'
ring from CMP sensor.
Refit
1.Ensure CMP sensor is clean, fit new 'O' ring
and sensor to cover.
2.Fit clamp to CMP sensor and tighten bolt to 8
Nm (6 lbf.ft).
3.Fit sensor multiplug to bracket and connect
engine harness to multiplug.
4.Fit engine oil filter.

+ ENGINE - V8, REPAIRS, Filter - oil.
5.Fit underbelly panel and secure with fixings.
6.Lower vehicle and connect battery earth lead.
7.Fit battery cover and secure with fixings.

ENGINE MANAGEMENT SYSTEM - V8
18-2-90 REPAIRS
Throttle Body
$% 19.22.45
Remove
1.Loosen 3 clips securing air intake hose, release
air intake hose and position aside.
Note: Pre 03 MY air intake hose illustrated.
2.Disconnect throttle and cruise control cables
from throttle body.
3.Loosen clip securing breather hose and release
hose. 4.Disconnect multiplug from throttle body.
5.Position a container below the throttle body to
collect coolant spillage.
6.Loosen 2 clips securing coolant hoses to
throttle body and release hoses.
7.Remove 4 bolts securing throttle body to
plenum chamber.
8.Remove throttle body and discard gasket.
Refit
1.Clean plenum chamber and throttle body
mating faces.
2.Using a new gasket, position throttle body, fit
bolts and tighten to 9 Nm (7 lbf.ft).
3.Connect coolant hoses to throttle body and
secure clips.
4.Connect breather hose to throttle body and
secure clip.
5.Connect multiplug to throttle body.
6.Connect throttle and cruise control cables.
l

+ ENGINE MANAGEMENT SYSTEM
- V8, ADJUSTMENTS, Cable - cruise
control.
l

+ ENGINE MANAGEMENT SYSTEM
- V8, ADJUSTMENTS, Cable - throttle.
7.Position air intake hose and secure clips.
8.Top-up cooling system.
M19 2576A
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