Crankshaft Position Sensor: Description and Operation

CRANKSHAFT POSITION (CKP) SENSORS

The crankshaft position (CKP) sensor has a 4-wire harness connector that plugs into the CKP sensor and connects to the ignition control module (ICM). The CKP sensor contains 2 hall-effect switches in 1 housing, and shares a magnet between the switches. The magnet and each hall-effect switch are separated by an air gap. A hall-effect switch is a solid state switching device that produces a digital ON/OFF pulse when a rotating element passes the sensor pick-up and interrupts the magnetic field of the sensor. The rotating element is called an interrupter ring or blade. There are two interrupter rings built into the crankshaft balancer. The outer ring and the outer switch provide the ICM with 18X signals or 18 identical pulses per crankshaft revolution. The inner ring and the inner switch provide the ICM with 3 pulses per revolution, each 1 of different duration. This is called the sync pulse. Each sync pulse represents a pair of companion cylinders. The ICM supplies a 12-volt and a low reference circuit to the CKP sensor, which is also shared by the camshaft position (CMP) sensor. The 18X reference pulses are passed from the CKP sensor to the ICM on the CKP sensor 1 signal circuit. The sync pulses are passed from the CKP sensor to the ICM on the CKP sensor 2 signal circuit. The ICM uses the 18X and sync pulses to determine the crankshaft position by counting how many ON-OFF 18X pulses occur during a sync pulse. With this dual interrupter ring arrangement the ICM can identify the correct pair of cylinders to fire within as little as 120 degrees of crankshaft rotation.