Discovery 2. Manual — part 484
ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-15
Input/Output
Electrical input to the camshaft position sensor is from fuse 2 located in engine compartment fuse box. One output is
sensor earth, the other is the signal output to the ECM via pin 20 of connector C0636.
The CMP sensor can fail the following ways or supply incorrect signal:
l
Sensor open circuit.
l
Short circuit to vehicle battery supply.
l
Short circuit to vehicle earth.
l
Incorrect fitting of the sensor.
l
Excessive camshaft gear wheel tolerance.
l
Excessive camshaft endfloat.
l
Camshaft and crankshaft misalignment.
l
Speed signal correlation with CKP sensor signal.
l
Cam wheel magnetised / residual magnetism
In the event of a CMP sensor signal failure any of the following symptoms may be observed:
l
Ignition timing reverts to default values from ECM memory.
l
Loss of cylinder correction.
l
Loss of active knock control.
l
Loss of active knock control diagnostics.
l
Loss of cylinder identification for misfire diagnostics.
l
Loss of quick synchronisation of crankshaft and camshaft for cranking/ start up.
l
Fuel injection could be 360
°
out of phase.
l
Front HO
2
S sensor ageing period diagnostic disabled (NAS only)
Should a malfunction of the component occur the following fault code may be evident and can be retrieved by
TestBook:
The fault condition has to be detected for more than 100 cam pulses (25 revolutions) when the engine speed is greater
than 500 rev/min.
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.
P code
J2012 description
Land Rover description
P0340
Camshaft position sensor circuit malfunction
Open/short circuit to vehicle supply or earth
ENGINE MANAGEMENT SYSTEM - V8
18-2-16 DESCRIPTION AND OPERATION
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.
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.
M124704A
0
20
40
60
80
100
120
140
160
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
V
k
Ω
k
Ω
V
°C
14
5
-5
0
-3
5
-2
0
-5
10
25
40
55
70
85
100
11
5
13
0
ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-17
The ECT sensor can fail the following ways or supply incorrect signal:
l
Sensor open circuit.
l
Short circuit to vehicle supply.
l
Short circuit to earth.
l
Incorrect mechanical fitting.
l
Signal fixed above 40
°
C (140
°
F) will not be detected.
l
Signal 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:
l
Difficult cold start.
l
Difficult hot start.
l
Driveability concern.
l
MIL illuminated.
l
Instrument cluster temperature warning lamp illuminated.
l
Temperature gauge reads excessively hot.
l
Temperature gauge reads excessively cold.
l
Cooling fan will not run.
There are three types of ECT sensor diagnostic checks:
l
The 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.
l
The 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.
l
The 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 problem
Signal 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
18-2-18 DESCRIPTION AND OPERATION
Thermostat Monitoring sensor
The thermostat monitoring sensor is located in the radiator, adjacent the bottom hose. The ECM compares the
temperature measured by the thermostat monitoring sensor to the temperature measured by the ECT sensor. If the
difference between the two readings is too great, the ECM determines the thermostat is stuck. In this case, the ECM
registers a fault code in its memory.
The thermostat monitoring sensor 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. With this
information, the ECM is able to monitor the performance of the thermostat. The normal operating parameters of the
thermostat monitoring sensor are as follows:
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