Crankshaft Position (CKP) Sensor (Engine management system - EDC)

Crankshaft Position (CKP) Sensor

The CKP sensor is located in the engine block, beneath the starter motor, with its tip adjacent to the outer circumference of the crankshaft reluctor ring.

The CKP sensor works on the variable reluctance principle. This uses the disturbance of the magnetic field which is set up around the CKP sensor, caused by the rotation of a reluctor 'target' attached to the crankshaft. The reluctor is a steel ring with 58 'teeth' and a space where two teeth are 'missing'. The teeth, and spaces between, each represent 3° of crankshaft rotation. The two missing teeth provide a reference for angular position. As the reluctor rotates adjacent to the sensor tip, a sinusoidal voltage waveform is produced which can be interpreted by the ECM into crankshaft angular position and velocity.

The signal from the CKP sensor is required by the ECM for the following functions: l To determine fuel injection timing. l To enable the fuel pump relay circuit (after the priming period). l To produce an engine speed message for broadcast on the CAN bus for use by other systems.

The two pins on the sensor are both outputs. To protect the integrity of the CKP signal the cable incorporates a screen. The cable screen earth path is via the ECM. Correct CKP sensor outputs are dependent upon the air gap between the tip of the CKP sensor and the passing teeth of the reluctor ring. The CKP air gap is not adjustable in this application.

In the event of a CKP sensor signal failure any of the following symptoms may be observed: l Engine cranks but fails to start. l Engine misfires. l Engine runs roughly or stalls.