Jeep Wagoneer/Commando/Cherokee 1984-1998

Crankshaft Position Sensor (CKP)



See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: View of the Crankshaft Position Sensor (CKP) and flywheel used on the Renix MPI system

The Crankshaft Position Sensor (CKP) is secured by special shouldered bolts to the flywheel/drive plate housing. It is preset in its mounting at the factory and is non-adjustable in the field. The sensor senses TDC and engine speed by detecting the flywheel teeth as they pass during engine operation.

The flywheel has a large trigger tooth and notch located 12 small teeth before each Top Dead Center (TDC) position. When a small tooth and notch pass the magnet core in the sensor, the concentration and then collapse of the magnetic flux induces a small voltage spike into the sensor pickup coil winding. These small voltage spikes enable the ECU to count the teeth as they pass the sensor.

When a large trigger tooth and notch pass the magnet core in the sensor, the increased concentration/collapse of the magnetic flux induces a higher voltage spike into the pickup coil winding. This higher voltage spike indicates to the ECU that a piston will soon be at the TDC position 12 teeth later. The ignition timing for the cylinder is either advanced or retarded as necessary by the ECU according to the sensor inputs.


Unplug the sensor connector from the ignition control module and connect an ohmmeter between terminals A and B as marked on the connector. The ohmmeter should read 125-275 ohms on a hot engine. Replace the sensor if the readings are not as stated.