2002 LAND ROVER DISCOVERY air condition

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-43
Operation - engine management
Fuel quantity
The ECM controls engine fuel quantity by providing sequential injection to the cylinders. Sequential injection allows
each injector to deliver fuel to the cylinders in the required firing order.
To achieve optimum fuel quantity under all driving conditions, the ECM provides an adaptive fuel strategy.
Conditions
Adaptive fuel strategy must be maintained under all throttle positions except:
lCold starting.
lHot starting.
lWide open throttle.
lAcceleration.
All of the throttle positions mentioned above are deemed to be 'open loop'. Open loop fuelling does not rely on
information from the HO
2 sensors, but the air/ fuel ratio is set directly by the ECM. During cold start conditions the
ECM uses ECT information to allow more fuel to be injected into the cylinders to facilitate cold starting. This strategy
is maintained until the HO
2 sensors are at working temperature and can pass exhaust gas information to the ECM.
Because of the specific nature of the other functions e.g. hot starting, idle, wide open throttle, and acceleration they
also require an 'open loop' strategy. For NAS vehicles with secondary air injection for cold start conditions, refer to
the Emissions section.

+ EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, Secondary air injection system.
Adaptive fuel strategy also allows for wear in the engine and components, as well as slight differences in component
signals, as no two components will give exactly the same readings.
Function
To be able to calculate the amount of fuel to be injected into each cylinder, the ECM needs to determine the amount
of air mass drawn into each cylinder. To perform this calculation, the ECM processes information from the following
sensors:
lMass air flow (MAF) sensor.
lCrank speed and position (CKP) sensor.
lEngine coolant temperature (ECT) sensor.
lThrottle position (TP) sensor.
During one engine revolution, 4 of the 8 cylinders draw in air. The ECM uses CKP sensor information to determine
that one engine revolution has taken place, and the MAF sensor information to determine how much air has been
drawn into engine. The amount of air drawn into each cylinder is therefore 1/4 of the total amount measured by the
ECM via the MAF sensor.
The ECM refers the measured air mass against a fuel quantity map in its memory and then supplies an earth path to
the relevant fuel injector for a period corresponding to the exact amount of fuel to be injected into the lower inlet
manifold. This fuel quantity is in direct relation to the air mass drawn into each cylinder to provide the optimum ratio.
During adaptive fuelling conditions, information from the heated oxygen sensors (HO
2S) is used by the ECM to correct
the fuel quantity to keep the air/ fuel ratio as close to the stoichiometric ideal as possible.

ENGINE MANAGEMENT SYSTEM - V8
18-2-44 DESCRIPTION AND OPERATION
Closed loop fuelling
The ECM uses a closed loop fuelling system as part of its fuelling strategy. The operation of the three-way catalytic
converter relies on the ECM being able to optimise the air/ fuel mixture, switching between rich and lean either side
of lambda one. Closed loop fuelling is not standard for all markets, vehicles that are not fitted with HO
2S do not have
closed loop fuelling.
The ideal stoichiometric ratio is represented by
λ =1. The ratio can be explained as 14.7 parts of air to every 1 part of
fuel.
Conditions
To achieve closed loop fuelling, the ECM interacts with the following components:
lHO
2S.
lFuel injectors.
Closed loop fuelling is a rolling process controlled by the ECM. The ECM uses information gained from the CKP, ECT,
MAF/ IAT and the TP sensors, to operate under the following conditions:
lPart throttle.
lLight engine load.
lCruising.
lIdle.
Function
When the engine is operating in the above conditions, the ECM implements the closed loop fuelling strategy. The air/
fuel mixture is ignited by the high tension (ht) spark in the combustion chambers and the resulting gas is expelled into
the exhaust pipe. Upon entering the exhaust pipe the exhaust gas passes over the protruding tip of the HO
2S. The
HO
2S measures the oxygen content of the gas compared to that of ambient air and converts it into a voltage, which
is measured by the ECM.
The voltage signal read by the ECM is proportional to the oxygen content of the exhaust gas. This signal can then be
compared to stored values in the ECM's memory and an adaptive strategy can be implemented.
If the HO
2S informs the ECM of an excess of oxygen (lean mixture), the ECM extends the opening time of the fuel
injectors via the Injector Pulse Width (IPW) signal. Once this new air/ fuel ratio has been 'burnt' in the combustion
chambers the HO
2S can again inform the ECM of the exhaust gas oxygen content, this time there will be a lack of
oxygen or a rich mixture. The ECM reduces the opening time of the injectors via the IPW signal using the ECM's
adaptive fuel strategy. During closed loop fuelling the HO
2S will constantly switch from rich to lean and back again,
this indicates that the ECM and the HO
2S are operating correctly.
Open loop fuelling
Open loop fuelling does not rely on information from the HO
2S, but the air/ fuel ratio is set directly by the ECM, which
uses information gained from the ECT, MAF/ IAT, the TP sensors and also the vehicle speed sensor (VSS). The ECM
uses open loop fuelling under the following conditions:
lCold start.
lHot start.
lWide open throttle.
lAcceleration.
The ECM uses open loop fuelling to control fuel quantity in all non adaptive strategy conditions. The ECM implements
fuelling information carried in the form of specific mapped data contained within its memory.
Because there is no sensor information (e.g. HO
2S), provided back to the ECM, the process is called an 'open loop'.
The ECM will also go into open loop fuelling if a HO
2S fails.

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-45
Ignition timing
The ignition timing is an important part of the ECM adaptive strategy. Ignition is controlled by a direct ignition system
using two four-ended coils operating on the wasted spark principle.
When the ECM triggers an ignition coil to spark, current from the coil travels to one spark plug, then jumps the gap at
the spark plug electrodes, igniting the mixture in the cylinder in the process. Current continues to travel along the earth
path (via the cylinder head) to the spark plug negative electrode at the cylinder that is on the exhaust stroke. The
current jumps across the spark plug electrodes and back to the coil completing the circuit. Since it has simultaneously
sparked in a cylinder that is on the exhaust stroke, it has not provided an ignition source there and is consequently
termed 'wasted'.
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.

ENGINE MANAGEMENT SYSTEM - V8
18-2-46 DESCRIPTION AND OPERATION
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.
Evaporative emission control
Due to increasing legislation, all new vehicles must be able to limit evaporative emissions (fuel vapour) from the fuel
tank.
The ECM controls the emission control system using the following components:
lEVAP canister.
lPurge valve.
lCanister vent solenoid (CVS) valve – (NAS vehicles with vacuum type EVAP system leak detection capability
only)
lFuel tank pressure sensor – (NAS vehicles with vacuum type EVAP system leak detection capability only)
lFuel leak detection pump – (NAS vehicles with positive pressure type EVAP system leak detection capability
only)
lInterconnecting pipe work.
Refer to Emissions section for operating conditions of evaporative emission systems.

+ EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, Evaporative emission control operation.
On-Board Diagnostics (OBD) - North American Specification vehicles only
The ECM monitors performance of the engine for misfires, catalyst efficiency, exhaust leaks and evaporative control
loss. If a fault occurs, the ECM stores the relevant fault code and warns the driver of component failure by illuminating
the Malfunction Indicator Light in the instrument pack.
On vehicles fitted with automatic gearbox, the ECM combines with the Electronic Automatic Transmission (EAT) ECU
to provide the OBD strategy.
Conditions
If the OBD function of the ECM flags a fault during its operation, it falls into one of the following categories:
lmin = minimum value of the signal exceeded.
lmax = maximum value of the signal exceeded.
lsignal = signal not present.
lplaus = an implausible condition has been diagnosed.

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-47
Function
All of the ECM's internal diagnostic fault paths are monitored by the OBD system. Specific faults have their own
numeric code relating to certain sensors or actuators etc. These specific faults fall into two types, error codes (E xxx)
or cycle codes (Z xxx). E codes represent instantaneous faults and Z codes relate to codes generated after completion
of a drive cycle.
If an emission relevant fault occurs on a drive cycle, the ECM stores a temporary fault code, if the fault does not occur
on subsequent drive cycles the fault code stays as a temporary fault code. If the fault recurs on subsequent drive
cycles the ECM stores the fault code as a permanent code, and depending on which component has failed the ECM
will illuminate the MIL.
Immobilisation system
The ECM and the body control unit (BCU) security system comprise the immobilisation system.
The ECM and the BCU combine to prevent the engine from running unless the appropriate security criteria are met.
The ECM and the BCU are a matched pair, if either one is replaced for any reason, the system will not operate unless
the replaced unit is correctly matched to its original specification. TestBook must be used to reconfigure the
immobilisation system.
Conditions
The ECM operates immobilisation in three states:
l'New'.
l'Secure'.
l'No Code'.
Function
With the ECM operating in the 'New' state, TestBook is required to instruct the ECM to learn the new BCU code. If the
ECM is in delivery state (i.e. direct from the supplier), it will not run the vehicle and will store a new ECM fault code
when it is fitted. This code must be cleared after instructing the ECM to learn the BCU code using TestBook.
When the ECM is in the 'Secure' state, no further action is required as the ECM has successfully learned the BCU
code. A 'Secure' ECM can not be configured to a 'No Code' state.
If the vehicle is fitted with an ECM with a valid code, the engine will start and the MIL will go out.
However, if the ECM has an invalid BCU security code the engine will crank, start, and then immediately stall. The
status of the security system can only be interrogated using TestBook.
TestBook is able to retrieve the following immobilisation fault codes:
P Code J2012 Description Land Rover Description
P1666 Engine anti-theft signal circuit malfunction BCU serial link frame/ bit timing error
P1667 Engine anti-theft signal circuit low Serial link short circuit to earth
P1668 Engine anti-theft signal circuit high Serial link open circuit
P1672 Engine anti-theft signal circuit wrong code
receivedSecure ECM, received incorrect code
P1673 Engine anti-theft signal new engine control
module not configuredNew ECM fitted
P1674 Engine anti-theft signal No code ECM, valid code received

ENGINE MANAGEMENT SYSTEM - V8
18-2-52 DESCRIPTION AND OPERATION
Function
The illumination of the low fuel level warning lamp in the instrument cluster triggers the low fuel level signal to be sent
to the ECM. This signal is processed via pin 8 of connector C0637 of the ECM.
Should a misfire occur while the fuel level is low, the following fault code may be evident and can be retrieved by
TestBook.
Coolant temperature gauge signal
The ECM controls the temperature gauge in the instrument cluster. The ECM sends a coolant temperature signal to
the temperature gauge in the instrument cluster in the form of a PWM square wave signal.
The frequency of the signal determines the level of the temperature gauge.
Conditions
The ECM operates the PWM signal under the following parameters:
l-40
°C (-40 °F) = a pulse width of 768 µs.
l140
°C (284 °F) = a pulse width of 4848 µs.
Function
The coolant temperature signal is an output from the ECM to the instrument cluster. The coolant temperature signal
is generated via pin 44 of connector C0636 of the ECM.
The coolant temperature signal can fail in the following ways:
lWiring short circuit to vehicle supply.
lWiring short circuit to vehicle earth.
lWiring open circuit.
In the event of a coolant temperature signal failure any of the following symptoms may be observed:
lCoolant temperature gauge will read cold at all times.
lCoolant temperature warning lamp remains on at all times.
Controller Area Network (CAN) system
The controller area network (CAN) system is a high speed serial interface between the ECM and the Electronic
Automatic Transmission (EAT) ECU. The CAN system uses a 'data bus' to transmit information messages between
the ECM and the EAT ECU. Because there are only two components in this CAN system, one will transmit information
messages and the other will receive information messages, and vice-versa.
Conditions
The CAN system is used by the EAT ECU and the ECM for transmission of the following information:
lGearshift torque control information.
lEAT OBD information.
lMIL request.
lVehicle speed signal.
lEngine temperature.
lEngine torque and speed.
lGear selected.
lGear change information.
lAltitude adaptation factor
lAir intake temperature
lThrottle angle / pedal position
P Code J2012 Description Land Rover Description
P1319 Misfire detected at low fuel level Misfire detected with low fuel level

COOLING SYSTEM - TD5
DESCRIPTION AND OPERATION 26-1-5
Description
General
The cooling system used on the Diesel engine is a pressure relief by-pass type system which allows coolant to
circulate around the engine block and heater circuit when the thermostat is closed. With coolant not passing through
the by-pass or the radiator promotes faster heater warm-up which in turn improves passenger comfort.
A coolant pump is mounted on a casting behind the PAS pump and is driven from the PAS pump at crankshaft speed
by the auxiliary drive belt. The pump mounting casting connects with passages in the cylinder block and pumps
coolant from the radiator through the cylinder block.
A viscous fan is attached to an idler pulley at the front of the engine. The fan is attached to a threaded spigot on the
pulley with a left hand threaded nut. The fan draws air through the radiator to assist in cooling when the vehicle is
stationary. The fan rotational speed is controlled relative to the running temperature of the engine by a thermostatic
valve regulated by a bi-metallic coil.
The cooling system uses a 50/50 mix of anti-freeze and water.
A Fuel Burning Heater (FBH) is available as an optional item for Diesel engine variants. The FBH is located on the
bulkhead and is connected in series in the coolant supply to the heater. The FBH is used to compensate for the
relatively low coolant temperatures inherent in the Diesel engine.

+ HEATING AND VENTILATION, DESCRIPTION AND OPERATION, Description.
Thermostat housing
A plastic thermostat housing is located behind the radiator. The housing has three connections which locate the
radiator bottom hose, top hose and coolant pump feed pipe. The housing contains a wax element thermostat and a
spring loaded by-pass flow valve.
Thermostat - Main valve
The thermostat is used to maintain the coolant at the optimum temperature for efficient combustion and to aid engine
warm-up. The thermostat is closed at temperatures below approximately 82
°C (179°F). When the coolant
temperature reaches approximately 82
°C the thermostat starts to open and is fully open at approximately 96°C
(204
°F). In this condition the full flow of coolant is directed through the radiator.
The thermostat is exposed to 90% hot coolant from the engine on one side and 10% cold coolant returning from the
radiator bottom hose on the other side.
Hot coolant from the engine passes from the by-pass pipe through four sensing holes in the flow valve into a tube
surrounding 90% of the thermostat sensitive area. Cold coolant returning from the radiator, cooled by the ambient air,
conducts through 10% of the thermostat sensitive area.
In cold ambient temperatures, the engine temperature is raised approximately 10
°C (50°F) to compensate for the heat
loss of 10% exposure to the cold coolant returning from the radiator bottom hose.
By-pass flow valve
The by-pass flow valve is held closed by a light spring. It operates to further aid heater warm-up. When the main valve
is closed and the engine speed is below 1500 rev/min, the coolant pump does not produce sufficient flow and pressure
to open the valve. In this condition the valve prevents coolant circulating through the by-pass circuit and forces the
coolant through the heater matrix only. This provides a higher flow of warm coolant through the heater matrix to
improve passenger comfort in cold conditions.
When the engine speed increases above 1500 rev/min the coolant pump produces a greater flow and pressure than
the heater circuit can take. The pressure acts on the flow valve and overcomes the valve spring pressure, opening
the valve and limiting the pressure in the heater circuit. The valve modulates to provide maximum coolant flow through
the heater matrix and yet allowing excess coolant to flow into the by-pass circuit to provide the engines cooling needs
at higher engine rev/min.

COOLING SYSTEM - TD5
26-1-10 DESCRIPTION AND OPERATION
Operation
Coolant flow - Engine warm up
Refer to illustration.

+ COOLING SYSTEM - Td5, DESCRIPTION AND OPERATION, Cooling system coolant flow.
During warm up the coolant pump moves fluid through the cylinder block and it emerges from the outlet housing. From
the outlet housing, the warm coolant flow is prevented from flowing through the upper and lower radiators because
both thermostats are closed. The coolant is directed into the heater circuit.
Some coolant from the by-pass pipe can pass through small sensing holes in the flow valve. The warm coolant enters
a tube in the thermostat housing and surrounds 90% of the thermostat sensitive area. Cold coolant returning from the
radiator bottom hose conducts through 10% of the thermostat sensitive area. In cold ambient temperatures the engine
temperature can be raised by up to 10
°C (50°F) to compensate for the heat loss of the 10% exposure to the cold
coolant return from the radiator bottom hose.
At engine speeds below 1500 rev/min, the by-pass valve is closed only allowing the small flow through the sensing
holes. As the engine speed increases above 1500 rev/min, the greater flow and pressure from pump overcomes the
light spring and opens the by-pass flow valve. The flow valve opens to meet the engine's cooling needs at higher
engine speeds and prevents excess pressure in the cooling system. With both thermostats closed, maximum flow is
directed through the heater circuit.
The heater matrix acts as a heat exchanger reducing the coolant temperature as it passes through the matrix. Coolant
emerges from the heater matrix and flows to the fuel cooler 'T' connection via the heater return hose. From the fuel
cooler the coolant is directed into the coolant pump feed pipe and recirculated around the heater circuit. In this
condition the cooling system is operating at maximum heater performance.
Coolant flow - Engine hot
As the coolant temperature increases the main thermostat opens. This allows some coolant from the outlet housing
to flow through the top hose and into the radiator to be cooled. The hot coolant flows from the left tank in the radiator,
along the tubes to the right tank. The air flowing through the fins between the tubes cools the coolant as it passes
through the radiator.
A controlled flow of the lower temperature coolant is drawn by the pump and blended with hot coolant from the by-
pass and the heater return pipes in the pump feed pipe. The pump then passes this coolant, via the cylinder block, to
the oil cooler housing, cooling the engine oil before entering the block to cool the cylinders.
When the fuel temperature increases, the heat from the fuel conducts through the fuel cooler 'T' connection and
causes the fuel thermostat to open.
Pre EU3 models: Coolant from the cylinder block flows through the oil cooler and via a pipe and hose enters the
lower radiator. The coolant in the lower radiator is subjected to an additional two passes through the lower radiator to
further reduce the coolant temperature. From the lower radiator the coolant flows , via a hose, to the fuel cooler.
As the hot fuel cools, travelling slowly forwards through the cooler, it meets the progressively colder coolant travelling
in the opposite direction from the lower radiator.
EU3 models: Coolant from the cylinder block flows through the oil cooler to the EGR cooler and then back to the
expansion tank. and via a pipe and hose enters the lower radiator. The lower temperature coolant from the oil cooler
housing is subjected to an additional two passes through the lower radiator to further reduce the coolant temperature.
From the lower radiator the coolant flows , via a hose, to the fuel cooler.
As the hot fuel cools, travelling slowly forwards through the cooler, it meets the progressively colder coolant travelling
in the opposite direction from the lower radiator.