HOLDEN GEN III V8, Service Training

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GEN III V8 ENGINE MANAGEMENT
CAMSHAFT POSITION SENSOR
The Camshaft Position (CMP) sensor is mounted through the top of the engine block at the rear of the valley
cover The CMP sensor works in conjunction with a "IX reluctor wheel on the camshaft The reluctor wheel is
inside the engine immediately in front of the rear cam bearing The PCM provides a 1 2 volt power supply to the
CMP sensor as well as an earth and a signal circuit
The PCM uses the CMP signal to determine if a
cylinder is on a firing stroke or on an exhaust
stroke As the camshaft rotates, the reluctor wheel
interrupts a magnetic field produced by a magnet
within the sensor The sensors internal circuitry
detects this and produces a signal which the PCM
reads The PCM uses this "IX signal in combination
with the Crankshaft Position sensor 24X signal in
order to determine crankshaft position and stroke
If the PCM is receiving a 24X Crankshaft Position
sensor signal, the engine will start even if there is
no CMP sensor signal The PCM cannot determine
when a particular cylinder is on either a firing or
exhaust stroke by the 24X signal alone, the PCM
requires the cam signal in order to determine if the
cylinder is on either the firing or exhaust stroke
If there is no CMP signal present the system
attempts synchronisation and looks for an increase
in MAP signal indicating the engine started If the
PCM does not detect a MAF increase, the PCM
assumes it incorrectly synchronised to the exhaust
stroke and re-synchs to the opposite cam position
A slightly longer cranking time may be a symptom
of this condition
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