Range Rover P38
19
FUEL SYSTEM
NEW RANGE ROVER
42
DESCRIPTION AND OPERATION
Camshaft Position (CMP) sensor - (from 99MY)
The CMP sensor is located at the front of the engine
block, above and behind the crankshaft pulley. The
sensor is clamped into position by means of a single
bolt. An ’O’ring is used to seal the interface between
the sensor and the aperture in the engine front cover.
The sensor has three wires which terminate in a
multiplug secured to a bracket on the left of the
crankshaft pulley. A short link lead is used to connect
the sensor to the engine harness. The wires to the
sensor have the following functions:
•
Power supply from engine compartment fusebox
•
Camshaft input signal to ECM
•
Screen to chassis ground connection
The CMP sensor is a Hall effect sensor which
produces four pulses for every two engine revolutions.
The sensing element is positioned less than 2mm
from the side of the camshaft gear wheel. The
camshaft gear wheel has four slots machined at
90
°
intervals which allows the identification of four
cylinder positions every camshaft revolution. Cylinder
recognition is used to enable sequential fuel injection
and knock control and is also used for diagnostic
purposes. The slots in the camshaft gear wheel are
shaped to provide unequal timing pulses for
determining TDC on No.1 cylinder. The camshaft and
crankshaft drives must also be correctly aligned, since
the ECM uses the crankshaft "missing teeth" marker
to determine crankshaft and camshaft position and
provide a reference mark which is 60
°
BTDC on No.1
cylinder.
The CMP sensor uses the Hall effect to act as a
magnetic switch for switching battery voltage on or off
depending on the position of the camshaft gear wheel
in relationship to the sensor. This results in a square
wave input between 0 and 12V at the ECM input pin.
Symptoms of a CMP sensor failure include the
following:
•
Ignition timing reverts to default values from
ECM memory with loss of cylinder correction.
•
Loss of active knock control and diagnostics.
•
Loss of cylinder identification for misfire
diagnostics.
•
Loss of quick synchronisation of crankshaft and
camshaft for cranking/start up.
•
Fuel injection could be 360
°
out of phase at
engine restart.
•
Front HO
2
S sensor ageing period diagnostic
could become disabled (NAS only).
The cause of CMP sensor failure may be attributable
to one of the following conditions:
•
Sensor open circuit.
•
Sensor signal line short circuit to vehicle battery
supply.
•
Sensor signal line or voltage supply line short
circuit to vehicle ground.
•
Incorrect fitting of the sensor.
•
Excessive camshaft gear wheel tolerance.
•
Excessive camshaft endfloat.
•
Camshaft and crankshaft misalignment.
•
Speed signal correlation with CKP sensor signal.
•
Cam wheel magnetised / residual magnetism.