Crankshaft Position Sensor
The Crankshaft Position (CKP) sensor mounts to the engine block behind the generator, just above the oil filter. See Fig 1 or Fig 2 . The CKP sensor is a Hall Effect sensor. The second crankshaft counterweight has two sets of four timing reference notches including a 60 degree signature notch. See Fig 3 . The PCM sends approximately 8 volts to the Hall Effect sensor. This voltage is required to operate the Hall Effect chip and the electronics inside the CKP sensor. A ground for the sensor is provided through the sensor return circuit. The input to the PCM occurs on a 5-volt output reference circuit. The notches generate pulses from high to low in the CKP sensor output voltage. When a metal portion of the counterweight aligns with the CKP sensor, the sensor output voltage goes low (less than 0.5 volt). When a notch aligns with the sensor, voltage goes high (5.0 volts). As a group of notches pass under the sensor, the output voltage switches from low (metal) to high (notch) then back to low. If available, an oscilloscope can display the square wave patterns of each voltage pulses. From the width of the output voltage pulses, the PCM calculates engine speed. The width of the pulses represent the amount of time the output voltage stays high before switching back to low. The period of time the sensor output voltage stays high before switching back to low is referred to as pulse width. The faster the engine is operating, the smaller the pulse width on the oscilloscope.