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Plug
a BNC test lead into channel A on the Scope , place a large black
crocodile clip on the test lead with the black moulding (negative) and
an acupuncture probe onto the test lead with the red moulding
(positive). Probe each of the two connections until the larger waveform
is displayed, the smaller waveform being the earth return.
Alternatively the AS-OS-02 two pin test lead adapter can be used, as illustrated in figure 14.1.6.
Fig.14.1.6
As
you will see in the preset scope picture and the example on this page
the waveform has been stabilised by using a falling trigger.
The
camshaft sensor is sometimes referred to as the Cylinder Identification
(CID) sensor or a 'phase' sensor and is used as a reference to time the
sequential fuel injection by the Electronic Control Module (ECM).
This particular type of sensor generates its own signal and therefore
does not require a voltage supply to power it and is recognisable by
its two electrical connections, with the occasional addition of a
coaxial shielding wire.
The
voltage produced by the camshaft sensor will be determined by several
factors, these being the engine's speed, the proximity of the metal
rotor to the pick-up and the strength of the magnetic field offered by
the sensor. The ECM needs to see the signal when the engine is started
for its reference; if absent it can alter the point at which the fuel
is injected. The driver of the vehicle may not be aware that the
vehicle has a problem if the CID sensor fails, as the drivability may
not be affected.
The
characteristics of a good inductive camshaft sensor waveform is a
sinewave that increases in magnitude as the engine speed is increased
and usually provides one signal per 720° of crankshaft rotation (360°
of camshaft rotation). The voltage will be approximately 0.5 volts peak
to peak while the engine is cranking, rising to around 2.5 volts peak
to peak at idle as seen in the example show. |
