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How they work
Crankshaft Position Sensor
The Crankshaft Position Sensor is attached to the engine block facing the timing rotor on the engine crankshaft.
The sensor detects signals used by the engine ECU to calculate the crankshaft position, and the engine rotational speed.
There are 2 types of the crankshaft position sensors. MPU type is explained here as reference.
34 teeth placed every 10° Crank Angle (CA), plus two missing teeth for Top Dead Center (TDC) detection are set around the outer diameter of the timing rotor. Therefore, 34 AC waves are outputted from the sensor for each revolution of the crankshaft. These AC waves are converted to rectangular waveforms by the waveform shaping circuit inside the engine ECU, and are used to calculate the crankshaft position, TDC, and the engine rotational speed.
Camshaft Position Sensor
The Camshaft Position Sensor detects camshaft rotation, and is mounted near the cylinder head so that the sensor is opposite to the timing rotor attached to the engine camshaft.
The engine ECU detects the camshaft angle, and performs cylinder recognition based on the signals detected by the camshaft position sensor.
There are 2 types of Camshaft Position Sensors. The MRE type is explained here as reference.
Due to timing rotor rotation, the direction of the magnetic field (magnetic vector) emitted from the sensor magnet changes according to the detection tooth position during the time when the detection tooth attached to the timing rotor approaches and then moves away from the camshaft position sensor. As a result, the MRE resistance value also changes. Voltage from the engine ECU is applied to the camshaft position sensor, and the change in MRE resistance value is outputted as a change in voltage. The waveforms of the outputs from the two MREs are differentially amplified, and shaped into a rectangular waveform by the amplification / waveform shaping circuit inside the sensor. The MRE outputs are then sent to the engine ECU.