Crankshaft Position Sensor: Description and Operation

CRANKSHAFT POSITION (CKP) SENSOR

The crankshaft position (CKP) sensor is a permanent magnet generator known as a variable reluctance sensor. The CKP sensor produces an AC voltage of varying amplitude and frequency. Frequency depends on the velocity of the crankshaft. AC voltage output depends on 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 ECM processes the pulses to create a signature pattern that enables the ECM to determine 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 and tachometer display. The ECM learns the variations between all of the 58 teeth under different speed and load conditions to correctly detect misfires.

The CKP sensor circuits consist of the following:
- A signal
- A low reference
- A ground

The ground wire is shielded to prevent electromagnetic interference in the CKP sensor circuits.