Camshaft Position (CMP) Sensor

CAMSHAFT POSITION (CMP) SENSOR

The camshaft position (CMP) sensor is a new version and operates using a different signal characteristic to previously.
- The sensor consists of an MRE (Magnetic Resistance Element). It is a permanent magnet with 2 special resistors which are connected in series with each other, where one end is voltage supplied and the other goes to ground. The output signal is an analog sine curve which passes through an analog/digital converter in the camshaft position (CMP) sensor before being sent on to the engine control module (ECM).
- When a tooth on the pulse wheel nears the sensor the magnetic field is bent and affects the resistor located nearest to the ground, resistance affects the voltage and the output signal to the Engine Control Module (ECM) is low. When the same tooth continues past the sensor the magnetic field follows and so affects the other resistor which is located nearest to the voltage supply, this resistor affects the voltage so that the output signal to the Engine Control Module (ECM) is high. The magnetic field swings backwards and forwards between the teeth on the pulse wheel and the engine control module (ECM) senses the signals between the teeth, partly before and partly after the sensor.
- The pulse wheel has 4 teeth. The engine control module (ECM) calculates the time interval from one tooth to the next and can decide exactly which cylinder must be supplied with fuel and spark respectively.