Moto Tech

🔧 Crankshaft Position Sensor (CKP) — Inductive vs. Hall Effect Explained ⚙️🚗

🔹 Inductive CKP Sensor
An inductive CKP sensor creates its own electrical signal without needing a reference voltage. It contains a coil and a permanent magnet.
When the teeth of the reluctor wheel (mounted on the crankshaft) pass in front of the sensor core, the magnetic field increases, and when the tooth moves away, the field decreases.
This change in magnetic flux causes the coil to cut magnetic lines and generate an AC voltage signal.
The resulting sine wave varies in amplitude and frequency based on engine speed:

At low RPM, the signal is weak

At high RPM, voltage increases

The ECU reads every zero-crossing point of this waveform as crankshaft position, allowing it to calculate ignition timing and injection synchronization.
A missing tooth on the reluctor wheel acts as the TDC reference, and if the sensor is too far away or covered with metallic debris, the signal weakens or becomes distorted.

🔹 Hall Effect CKP Sensor
A Hall sensor operates with a 5V or 12V supply, a ground, and a digital signal wire.
Unlike the inductive type, it doesn’t produce a sine wave—its output is a clean square wave, switching sharply between 0V and the reference voltage.
Each time a tooth passes in front of the sensor, it disrupts the magnetic field; the internal Hall chip detects this change and sends a precise digital pulse to the ECU.

This design allows for accurate readings even at low RPM, making it ideal for modern engines with fast starts and advanced timing systems.
If the Hall signal has drops or interruptions, the ECU loses crankshaft reference, causing:

Hard starting

Stalling when warm

Loss of synchronization with the CMP sensor

🔸 Both sensors perform the same essential function—reporting exact crankshaft position—but rely on different physical principles:

The inductive sensor generates voltage through magnetic induction

The Hall effect sensor detects magnetic changes electronically