definition of crankshaft sensor
The crankshaft position sensor (CKP sensor or CPS) is one of several sensors that keep your engine running smoothly. It measures the position of the crankshaft (for which it is sometimes called the crank angle sensor or CAS), as well as the rotational speed of the crankshaft (for which it is sometimes called the engine speed sensor, ESS, or the RPM sensor). The crankshaft position sensor relays this information to the vehicle's onboard computer, the engine control unit (ECU).