Crankshaft Position Sensor: Description and Operation

The Engine Speed Sensor, also referred to as the Crankshaft Position Sensor, is mounted to the front of the engine. It generates an RPM signal to the PCM. The engine speed sensor input is used along with the Vehicle Speed Sensor and the Throttle Position Sensor to determine when to shift the automatic transmission into overdrive, as well as for tachometer and speed control inputs. The speed sensor signal is also used as an input for the ASD relay, for control of the alternator field circuit.