Discovery 2. Manual — part 72

ENGINE MANAGEMENT SYSTEM - V8

DESCRIPTION AND OPERATION 18-2-17

Camshaft Position (CMP) sensor (C0176)

The CMP sensor is located on the front of the engine, above and behind the crankshaft pulley. The CMP sensor is a
Hall effect sensor producing four pulses for every two crankshaft revolutions. The sensor is positioned close to the
camshaft gear wheel, the gear wheel has four slots machined at 90

°

intervals. This allows the ECM to recognise 4

individual cylinders every camshaft revolution or all 8 cylinders every crankshaft revolution.

The CMP sensor Hall effect works as a magnetic switch. It switches battery voltage on or off depending on the position
of the camshaft gear wheel in relationship to the sensor.

The ECM uses this signal for cylinder recognition to control sequential fuel injection, engine knock and diagnostic
purposes.

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.

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

18-2-18 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

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:

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.

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

145

-5

0

-35

-2

0

-5

10

25

40

55

70

85

100

11

5

13

0

ENGINE MANAGEMENT SYSTEM - V8

18-2-20 DESCRIPTION AND OPERATION

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