Cherokee 4WD L6-4.0L VIN S (1998)
Sensor Operation
The flywheel/drive plate has groups of four notches at its outer edge. On 4.0L 6-cylinder engines there are three sets of notches. On 2.5L
4-cylinder engines there are two 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 two groups of four pulses generated on 2.5L 4-cylinder engines. There are 3 groups of four pulses generated on 4.0L 6-cylinder
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.
