Crankshaft Position Sensor: Description and Operation

CRANKSHAFT POSITION SENSOR-PCM INPUT
This sensor is a hall effect device that detects notches in the flywheel (manual transmission) or flexplate (automatic transmission).

This sensor is used to indicate to the Powertrain Control Module (PCM) that a spark and or fuel injection event is to be required. The output from this sensor, in conjunction with the camshaft position sensor signal, is used to differentiate between fuel injection and spark events.

SYSTEM OPERATION

Crankshaft Position Sensor - Auto Trans:

Crankshaft Position Sensor - Manual Trans:

The crankshaft position sensor is mounted to the transmission bellhousing at the left/rear side of the engine block.

Engine speed and crankshaft position are provided through the crankshaft position sensor. The sensor generates pulses that are the input sent to the Powertrain Control Module (PCM). The PCM interprets the sensor input to determine the crankshaft position. The PCM then uses this position, along with other inputs, to determine injector sequence and ignition timing.

The sensor is a hall effect device combined with an internal magnet. It is also sensitive to steel within a certain distance from it.

Sensor operation

Sensor Operation - 4.0L Manual Transmission:

Sensor Operation - 4.0L Automatic Transmission:

The flywheel/drive plate has groups of four notches at its outer edge. On these engines there are three sets of notches.

The notches cause a pulse to be generated when they pass under the sensor. The pulses are the input to the PCM. For each engine revolution There are 3 groups of four pulses generated on these engines.

The trailing edge of the fourth notch, which causes the pulse, is four degrees before top dead center (TDC) of the corresponding piston.

The engine will not operate if the PCM does not receive a crankshaft position sensor input.