1999 LAND ROVER DISCOVERY engine oil

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-41
Input/Output
Input to the low tension side of the ignition coils comes from Fuse 14 located in the passenger compartment fuse box.
This fuse provides battery power for two ignition coils.
It is possible to test both primary and secondary coils of the ignition coils for resistance using a multimeter as follows:
lExpected primary coil resistance: 0.5 ± 0.05 Ω at 20 °C (68 °F).
lExpected secondary coil resistance: 13.3 ± 1.3 kΩ at 20 °C (68 °F).
The ECM provides the earth control for each coil on separate pins as follows:
LH Bank (cylinders 1, 3, 5, 7)
lCylinder 1 - pin 6 of connector C0638 of the ECM multiplug.
lCylinder 3 - pin 2 of connector C0638 of the ECM multiplug.
lCylinder 5 - pin 8 of connector C0638 of the ECM multiplug.
lCylinder 7 - pin 7 of connector C0638 of the ECM multiplug.
RH Bank (cylinders 2, 4, 6, 8)
lCylinder 2 - pin 2 of connector C0638 of the ECM multiplug.
lCylinder 4 - pin 7 of connector C0638 of the ECM multiplug.
lCylinder 6 - pin 6 of connector C0638 of the ECM multiplug.
lCylinder 8 - pin 8 of connector C0638 of the ECM multiplug.
The ignition coil can fail the following ways or supply incorrect signal:
lCoil open circuit.
lShort circuit to vehicle supply.
lShort circuit to vehicle earth.
lFaulty component.
In the event of ignition coil failure any of the following symptoms may be observed:
lEngine misfire on specific cylinders.
lEngine will not start.

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-43
The ECM performs the following diagnostic checks to confirm correct knock sensor operation:
lKS signal level is less than the minimum threshold (dependent on engine speed) – the engine must be running,
coolant temperature above 60°C (140°F), number of camshaft revolutions since start greater than 50 and the KS
signal profile must be less than the threshold value at a given engine speed for a fault condition to be flagged
lKS signal is greater than the maximum threshold (dependent on engine speed) – the engine must be running,
coolant temperature above 60°C (140°F), number of camshaft revolutions since start greater than 50 and the KS
signal profile must be greater than the threshold value at a given engine speed for a fault condition to be flagged
lError counter for verification of knock internal circuitry exceeded – the engine must be running, coolant
temperature above 60°C (140°F), number of camshaft revolutions since start greater than 50 and the error
counter greater than the threshold value at a given engine speed for a fault condition to be flagged
Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by
TestBook:
Spark plugs
The spark plugs are platinum tipped on both centre and earth electrodes. The platinum tips give a long maintenance
free life.
Cleaning or resetting the spark plug gap is not recommended as this could result in damaging the platinum tips and
thereby reducing reliability.
The misfire detection system will malfunction and store erroneous codes if the incorrect spark plugs are used.
Input/Output
The ignition coils provide a voltage to the spark plugs via the ht leads. The cylinder head via the individual thread of
each spark plug provides the earth path.
The spark plugs can fail in the following ways:
lFaulty component.
lConnector or wiring fault.
lBreakdown of high tension lead causing tracking to chassis earth.
lIncorrect spark plugs fitted.
In the event of a spark plug failure, misfire on specific cylinder may be observed:
P Code J2012 Description Land Rover Description
P0327 Knock sensor 1 circuit low input (bank 1 or single
sensor)LH bank signal less than threshold determined from
ECM model above 2200 rev/min
P0328 Knock sensor 1 circuit high input (bank 1 or
single sensor)LH bank signal greater than threshold determined from
ECM model above 2200 rev/min
P0332 Knock sensor 2 circuit low input (bank 2) RH bank signal less than threshold determined from
ECM model above 2200 rev/min
P0333 Knock sensor 2 circuit high input (bank 2) RH bank signal greater than threshold determined from
ECM model above 2200 rev/min

ENGINE MANAGEMENT SYSTEM - V8
18-2-44 DESCRIPTION AND OPERATION
High tension (ht) leads
The ht leads are located on top of the engine, below the plenum chamber. Their function is to transfer the ht voltage
generated by the ignition coils to the spark plugs in the engine.
Input/Output
The input to the ht lead is ht voltage from the ignition coil pack. The ht lead then supplies this voltage to the spark
plug. Output ht voltage is used by the spark plugs to ignite the air/fuel mixture in the combustion chamber.
The ht leads can fail in the following ways:
lConnector/ Wiring fault.
lFaulty component causing spark tracking to chassis earth.
lDamage to ht leads during component removal.
In the event of a ht lead failure the following symptom may be observed:
lMisfire on specific cylinder.
All ignition system related faults are diagnosed by the misfire detection system and its fault codes.
Hill Decent Control (HDC)
Refer to Brakes for description of the hill descent control.

+ BRAKES, DESCRIPTION AND OPERATION, Description.
High/Low ratio switch
Refer to Transfer Box for description of the high/ low ratio switch transfer box components.

+ TRANSFER BOX - LT230SE, DESCRIPTION AND OPERATION, Description.

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-47
ATC compressor clutch relay
The ATC compressor clutch 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 ATC compressor clutch.
Input/Output
The ECM provides the earth for the relay coil to allow the relay contacts to close and the ATC 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 coil.
When the ECM opens the earth path, the return spring in the relay will pull the contacts apart to shut down the ATC
clutch drive.
Input to the ATC clutch relay switching contacts is via fuse 6 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 coil is via pin 29 of the ECM C0657 connector. When the relay is energised the output from the
switching contacts goes directly to the ATC compressor clutch.
The ATC clutch relay can fail in the following ways:
lRelay open circuit.
lShort circuit to vehicle supply.
lShort circuit to vehicle earth.
lBroken return spring.
In the event of an ATC clutch relay failure, the ATC does not work.
Should a malfunction of the component occur, the following fault codes may be evident and can be retrieved by
TestBook.
P Code J2012 Description Land Rover Description
P1536 Air conditioning compressor request range/
performanceATC compressor clutch relay open circuit
P1537 Air conditioning compressor request low input ATC compressor clutch relay short to earth
P1538 Air conditioning compressor request high input ATC compressor clutch relay short to battery supply

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
18-2-50 DESCRIPTION AND OPERATION
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.
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'.

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
18-2-80 REPAIRS
Coil - ignition
$% 18.20.45
Remove
1.Remove upper inlet manifold assembly.

+ MANIFOLDS AND EXHAUST
SYSTEMS - V8, REPAIRS, Gasket - inlet
manifold - upper - Without Secondary Air
Injection.
2.Disconnect multiplugs from ignition coils.
3.Release ht leads from rocker covers and
disconnect ht leads from spark plugs.
4.Carefully manoeuvre ignition coil assembly
from between engine and bulkhead. 5.Noting their fitted position disconnect ht leads
from ignition coil.
6.Remove 3 screws securing ignition coil to
support bracket and remove coils.
Refit
1.Position ignition coil to support bracket, fit and
tighten screws.
2.Connect ht leads to ignition coil ensuring they
are in the correct position.
3.Carefully position ignition coil assembly
between engine and bulkhead.
4.Connect ht leads to spark plugs and secure ht
leads to rocker covers.
5.Connect multiplugs to ignition coils.
6.Fit upper inlet manifold assembly.

+ MANIFOLDS AND EXHAUST
SYSTEMS - V8, REPAIRS, Gasket - inlet
manifold - upper - Without Secondary Air
Injection.