Crankshaft Position Sensor (4.0L)
Crankshaft Position (CKP) sensor is located near the outer edge of the flywheel (starter ring gear). See Fig 1 or Fig 2 . Engine speed and crankshaft position are provided through the CKP sensor. The sensor generates input pulses that are sent to the Powertrain Control Module (PCM). The PCM interprets the sensor input to determine 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.
The flywheel/drive plate has groups of 4 notches at its outer edge. There are 3 sets of notches. See Fig 3 . On all engines, 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 4 pulses generated on the 4.0L. The trailing edge of the fourth notch, which causes the pulse, is 4 degrees before top dead center of the corresponding piston. The engine will not operate if the PCM does not receive a CKP sensor input.