Crankshaft position sensor

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A crank sensor (CKP)^[1][2][3] is an electronic device used in an internal combustion engine, both petrol and diesel, to monitor the position or rotational speed of the crankshaft. This information is used by engine management systems to control the fuel injection or the ignition system timing and other engine parameters. Before electronic crank sensors were available, the distributor would have to be manually adjusted to a timing mark on petrol engines.

The crank sensor can be used in combination with a similar camshaft position sensor (CMP)^[4][5][3] to monitor the relationship between the pistons and valves in the engine, which is particularly important in engines with variable valve timing. This method is also used to "synchronise" a four stroke engine upon starting, allowing the management system to know when to inject the fuel. It is also commonly used as the primary source for the measurement of engine speed in revolutions per minute.

Common mounting locations include the main crank pulley, the flywheel, the camshaft or on the crankshaft itself. This sensor is one of the two most important sensors in modern-day engines, together with the camshaft position sensor. As the fuel injection (diesel engines) or spark ignition (petrol engines) is usually timed from the crank sensor position signal, failing sensor will cause an engine not to start or will cut out while running. Engine speed indicator takes speed indication also from this sensor.