coolant temperature LAND ROVER DISCOVERY 1999 User Guide

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-3
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 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
18-2-6 DESCRIPTION AND OPERATION
Description - engine management
General
The V8 engine is equipped with the Bosch Motronic M5.2.1 engine management system. This system is a sequential
multiport fuel injection system controlled by an Engine Control Module (ECM).
A single ECM is used for the control of the existing 4.0 litre engine and the new 4.6 litre engine introduced with 03
model year vehicles for the NAS market only. The ECM contains the tunes for both engines variants. When the ECM
is replaced, TestBook/T4 must be used to select the correct tune to match the engine fitment.
The ECM has On Board Diagnostic (OBD) strategies as required by various market legislative bodies. To meet these
requirements the system monitors and reports on any faults that cause excessive exhaust emissions.
In markets that mandate OBD, 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.
In markets where OBD is not mandatory, the ECM will still monitor performance of the engine and store the fault code,
but will not illuminate the Malfunction Indicator Light.
The ECM uses input and output information from its sensors and actuators to control the following engine conditions:
lFuel quantity.
lClosed loop fuelling.
lOpen loop fuelling.
lIgnition timing.
lKnock control.
lIdle speed control.
lEmission control.
lOn-Board Diagnostic (OBD) where applicable.
lVehicle immobilisation.
lMisfire detection (where applicable).
lVehicle speed signal.
lRough road signal (where applicable).
lLow fuel level signal (where applicable).
lCoolant temperature gauge signal.
The ECM processes sensor information from the following input sources:
lIgnition switch (position II).
lCrankshaft speed and position sensor.
lCamshaft position sensor.
lEngine coolant temperature sensor.
lMass air flow sensor.
lIntake air temperature sensor.
lKnock sensor.
lThrottle position sensor.
lHeated oxygen sensors.
lHigh/ Low ratio switch.
lFuel tank pressure sensor (where fitted)
lThermostat monitoring sensor (where fitted)

ENGINE MANAGEMENT SYSTEM - V8
18-2-10 DESCRIPTION AND OPERATION
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
42 Idle air control valve open Output, signal PWM 12-0V
43 Idle air control valve close Output, signal PWM 12-0V
44 ECT sensor signal Output, signal PWM 0-12V

ENGINE MANAGEMENT SYSTEM - V8
18-2-18 DESCRIPTION AND OPERATION
Engine Coolant Temperature (ECT) sensor (C0196)
The ECT sensor is located at the front of the engine adjacent to the coolant outlet pipe. The ECT sensor forms a vital
part of the ECM operating strategy, and therefore the optimum control of the running of the engine. Richer air/ fuel
ratio is required at lower coolant temperatures such as cold starting. Coolant temperature information from the ECT
sensor is also vital to enable the ECM to weaken the air/ fuel mixture as temperature rises to maintain low emissions
and optimum performance.
For NAS vehicles with secondary air injection, the signal from the ECT sensor is monitored at engine start, to
determine whether the conditions are cold enough to warrant secondary air injection to be employed. The ECT sensor
is then monitored to switch off the secondary air injection when the required engine coolant temperature has been
attained.

+ EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, Secondary Air Injection System.
The ECT works as a Negative Temperature Coefficient (NTC) sensor. As temperature rises, the resistance in the
sensor decreases, as temperature decreases, the resistance in the sensor increases. The ECT sensor forms part of
a voltage divider chain with a pull up resistor within the ECM. Consequently as the ECT sensor resistance changes,
the analogue voltage at the input signal from the ECT sensor to the ECM will be adjusted which corresponds to the
temperature of the engine coolant. With this information, the ECM can implement the correct strategies for cold start,
warm up etc. The ECM supplies the instrument cluster with a pulse width modulated (PWM) coolant temperature
signal to drive the temperature gauge.

ENGINE MANAGEMENT SYSTEM - V8
18-2-20 DESCRIPTION AND OPERATION
There are three types of ECT sensor diagnostic checks:
lThe ECT sensor signal is within limits, but is inaccurate – the engine has to be running and the signal indicates
a coolant temperature below 40°C (104°F). The signal differs too much from the coolant temperature model for
longer than 2.53 seconds.
lThe ECT sensor signal is greater than the maximum threshold value – the ECM has to be powered up to perform
the diagnostic, but the engine does not need to be running.
lThe ECT sensor signal is less than the minimum threshold value – the ECM has to be powered up to perform
the diagnostic, but the engine does not need to be running.
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
P0116 Engine coolant temperature circuit/range
performance problemSignal differs too much from temperature model for
longer than 2.53s
P0117 Engine coolant temperature circuit low input Open circuit or short circuit to battery supply
P0118 Engine coolant temperature circuit high input Short circuit to earth

ENGINE MANAGEMENT SYSTEM - V8
18-2-22 DESCRIPTION AND OPERATION
Input/Output
The ECM provides the thermostat monitoring sensor with a 5 volt reference via pin 21 of connector C0635 of the ECM,
and an earth via pin 5 of connector C0635 of the ECM.
There are three types of thermostat monitoring sensor diagnostic checks:
lSensor signal is above maximum threshold. For the ECM to register this as a fault, and illuminate the MIL, the
temperature registered by the thermostat monitoring sensor must be above 140 °C (284 °F) for more than 1
second.
lSensor signal is below minimum threshold. For the ECM to register this as a fault, and illuminate the MIL, the
temperature registered by the thermostat monitoring sensor must be below -33 °C (-27 °F) for more than 1
second, while the inlet air temperature reading is greater than -32 °C (-25 °F).
lSignal difference between ECT sensor and thermostat monitoring sensor is below maximum threshold. For the
ECM to register this as a fault, and illuminate the MIL, the following conditions must exist:
lNo maximum or minimum threshold signal faults exist.
lNo faults are recorded against the thermostat monitoring sensor or vehicle speed signal.
lEngine not in idle speed control.
lFuel cut-off not active.
lEngine speed is greater than 400 rpm.
lRoad speed is greater than 0 mph.
lIntegrated mass air flow from engine start to fuel cut-off is greater than set value (between 3 kg and 10 kg
dependent upon engine coolant temperature at engine start).
lEngine coolant temperature at engine start is between 9 °C and 39 °C (48 °F and 102 °F).
lHigh range is selected.
lDelay time before thermostat monitoring is enabled is between set limits (between 50 and 500 seconds
dependent upon engine coolant temperature at engine start).
lEngine coolant temperature is greater than 90 °C (194 °F).
lThe difference between the ECT sensor reading and the thermostat monitoring sensor reading is less than
39 °C (102 °F).

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-23
Should a malfunction occur, the following fault codes may be evident and can be retrieved by TestBook:
Mass Air Flow (MAF)/ Inlet Air Temperature (IAT) sensor (C0149)
The MAF/ IAT sensors are combined into a single unit and located between the air filter housing and the inlet manifold.
The ECM receives input signals from the MAF/ IAT sensor to calculate the mass of air flowing into the engine inlet
manifold.
Input/Output
The MAF sensor has both electrical input and output. Input to the MAF sensor comes from two different sources.
Battery voltage is supplied to the MAF sensor via fuse 2 of the engine compartment fuse box. The MAF sensor also
utilises a 5 volt reference input via pin 7 of connector C0636 of the ECM. The MAF sensor output voltage is measured
via pin 23 of connector C0636 of the ECM.
The IAT sensor has only electrical output. Output from the IAT sensor is measured at pin 34 of connector C0636 of
the ECM, this is a variable voltage/ resistance measured by the sensor to provide air temperature information to the
ECM.
The MAF/ IAT sensor share the same sensor earth. Sensor earth is via pin 9 of connector C0636 of the ECM.
The MAF/ IAT sensor and its connector has silver plated terminals for its low current signals to protect against
corrosion. DO NOT apply 12V to the 5V supply, as this will destroy the internal circuitry. The MAF/IAT sensor should
not be dropped or roughly handled and should be kept free from contamination.
P code J2012 description Land Rover description
P1117 Radiator outlet temperature
thermister lowThermostat reading below -33 °C (-
27 °F)
P1118 Radiator outlet temperature
thermister highThermostat reading above 140 °C
(284 °F)
P0126 Engine thermostat defective Difference in radiator and engine
coolant temperatures too small

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-29
In the event of a TP sensor signal failure any of the following symptoms may be observed:
lEngine performance concern.
lDelayed throttle response.
lFailure of emission control.
lClosed loop idle speed control inoperative.
lAutomatic gearbox kickdown inoperative.
lIncorrect altitude adaptation.
lMIL illuminated (NAS only).
There are three throttle position sensor diagnostic checks:
lTP sensor signal is greater than the maximum threshold value – the engine speed must be greater than 400 rev/
min for longer than 2 seconds and the signal must be greater than 96% for longer than 50 ms.
lTP sensor signal is less than the minimum threshold – the engine speed must be greater than 400 rev/min for
longer than 2 seconds and the signal must be less than 4% for longer than 50 ms.
lRatio of throttle position to mass of air flow – the calculated throttle angle must be outside limits when the engine
speed is between 800 rev/min and 4000 rev/min, the engine load is between 2 and 6.5 and the coolant
temperature is above -10°C (14°F).
Should a malfunction of the TP sensor occur the following fault codes may be evident and can be retrieved by
TestBook.
P code J2012 description Land Rover description
P0101 Mass or volume air flow circuit range/
performance problemLoad monitoring, the ratio of throttle position to air flow
P0122 TPS a circuit low input Signal < minimum threshold
P0123 TPS a circuit high input Signal > maximum threshold

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