Crankshaft Position Sensor: Description and Operation

CRANKSHAFT POSITION (CKP) SENSOR

The crankshaft position (CKP) sensor is a hall-effect sensor. An integrated circuit (IC) magnetic sensing element inside the sensor is magnetically biased by a permanent magnet located within the sensor. The CKP sensor circuits consist of a 12-volt reference circuit, a low reference circuit, and a signal circuit. The CKP sensor produces a DC voltage of varying amplitude and frequency. The frequency depends on the velocity of the crankshaft and the DC output voltage depends on the crankshaft position and battery voltage. The CKP sensor works in conjunction with a 58-tooth reluctor wheel attached to the crankshaft. As each reluctor wheel tooth rotates past the CKP sensor, the resulting change in the magnetic field is used by the sensor electronics to produce a digital output pulse. The sensor returns a digital ON/OFF pulse 58 times per crankshaft revolution. The engine control module (ECM) processes the digital pulse to create a signature pattern that enables the ECM to determine the crankshaft position. The CMP sensor signal is used to determine the position of the valve train relative to the crankshaft position. The ECM can synchronize the ignition timing, the fuel injector timing, and the spark knock control based on the CKP sensor and CMP sensor inputs. The CKP sensor is also used to detect misfire.