Camshaft Position Sensor: Description and Operation

Camshaft Position Sensor

Description
The camshaft position is determined by a Hall effect sensor that detects the passing of a cam profile on the camshaft. The sensor produces one pulse for each camshaft revolution and is used to synchronise the injectors so that fuel is injected into the correct cylinder at the right time.

The sensor is, in effect, a magnetically operated electrical switch. The sensor operates by switching a battery positive supply voltage on or off dependent on the presence or absence of the metal teeth in close proximity to the sensor. As the tooth passes in front of the sensor, it closes the magnetic circuit of the sensor, which in turn activates the 'switch'.

The 'pulse train' generated by the 'switching' of the camshaft position sensor has varying tooth width and tooth gap ratios in order to allow cylinder identification.

There are two diagnostic checks on the output signal of this sensor: -
1. A lack of signal of invalid signal. A fault is detected if the signal is high at 162 degrees or low at 522 degrees after top dead center (TDC) for Number 1 cylinder firing.
2. A rationality check of the camshaft position signal with respect to the crankshaft position signal. A fault is detected if the camshaft position signal state transition is not within the following window -270 degrees to 372 degrees and 654 degrees to 12 degrees crankshaft after TDC for number 1 cylinder firing.