<P> Some engines, such as GM's Premium V family, use crank position sensors which read a reluctor ring integral to the harmonic balancer . This is a much more accurate method of determining the position of the crankshaft, and allows the computer to determine within a few degrees the exact position of the crankshaft (and thereby all connected components) at any given time . </P> <P> The functional objective for the crankshaft position sensor is to determine the position and / or rotational speed (RPM) of the crank . Engine Control Units use the information transmitted by the sensor to control parameters such as ignition timing and fuel injection timing . In a diesel the sensor will control the fuel injection . The sensor output may also be related to other sensor data including the cam position to derive the current combustion cycle, this is very important for the starting of a four stroke engine . </P> <P> Sometimes, the sensor may become burnt or worn out - or just die of old age at high mileage . One likely cause of crankshaft position sensor failure is exposure to extreme heat . Others are vibration causing a wire to fracture or corrosion on the pins of harness connectors . Many modern crankshaft sensors are sealed units and therefore will not be damaged by water or other fluids . When it goes wrong, it stops transmitting the signal which contains the vital data for the ignition and other parts in the system . </P> <P> A bad crank position sensor can worsen the way the engine idles, or the acceleration behaviour . If the engine is revved up with a bad or faulty sensor, it may cause misfiring, motor vibration or backfires . Acceleration might be hesitant, and abnormal shaking during engine idle might occur . In the worst case the car may not start . </P>

What is the purpose of the camshaft position sensor