Crankshaft Position Sensor: Description and Operation

The flywheel/flexplate housing mounted speed sensor is used to provide the ECU with engine speed and crankshaft position information. The flywheel/flexplate is provided with large trigger teeth every 90 degrees (TDC of every cylinder) and 12 small trigger teeth before each of the larger teeth. As the flywheel rotates, the speed sensor can determine exactly where the crankshaft is and the speed with which it is turning through the use of a magnetic field.