Crankshaft Position Sensor

The crankshaft position sensor is installed on the oil pump which is located in the front center portion of the cylinder block. The sensor generates a pulse when one of the teeth on the perimeter of the crankshaft sprocket (rotating together with the crankshaft) passes in front of it. The ECM determines the crankshaft angular position by counting the number of pulses.
The crankshaft position sensor is a magnet pickup type and is molded with components such as a magnet, core, coil, and terminal, etc.

Fig 1: Identifying Crankshaft Position Sensor Elements
Courtesy of SUBARU OF AMERICA, INC.
As the crankshaft rotates, each tooth aligns with the crankshaft position sensor. At that time, the magnetic flux in the sensor's coil changes since the air gap between the sensor pickup and the sprocket changes. This change in magnetic flux induces a voltage pulse in the sensor and the pulse is transmitted to the ECM.

Fig 2: Identifying Crankshaft Position Sensor And Sprocket
Courtesy of SUBARU OF AMERICA, INC.