Crankshaft position sensor

BASIC IGNITION TIMING - VVC

Crankshaft position sensor

The speed and position of the engine is detected by the crankshaft position sensor which is bolted to, and projects through, the engine adapter plate adjacent to the flywheel.

The crankshaft position sensor is an inductive sensor consisting of a bracket mounted body containing a coil and a permanent magnet which provides a magnetic field. The sensor is situated such that an air gap exists between it and the flywheel. Air gap distance is critical for correct operation.

The flywheel incorporates a reluctor ring which consists of 32 poles spaced at 10° intervals, with 4 missing poles at 30°, 60°, 210°and 250°. When the flywheel rotates, as a pole passes the CKP sensor, it disturbs the magnetic field, inducing a voltage pulse in the coil, which is transmitted to the ECM.

By calculating the number of pulses that occur within a given time, the ECM can determine the engine speed. The output from this sensor when used in conjunction with that from the manifold absolute pressure sensor provides idle stabilisation and reference for both ignition and injection timing.

Camshaft position sensor

The camshaft position sensor has two functions. The first is to enable the ECM to run a sequential fuelling mode. The second is to measure the actual cam period, this measurement is achieved using teeth on the camshafts to indicate when the valve opens and closes.

If the camshaft position sensor fails when the engine is running, the engine will continue to run normally in sequential fuelling mode. If the sensor fails before the engine is started, the engine will start but run in grouped fuelling mode. The engine running in grouped fuelling mode can be detected by a reduced rev limit: 5500/5800 rpm in comparison to the normal rev limit of 7000/7300 rpm. Camshaft position sensor failure can be identified using TestBook.