Camshaft position (CMP) sensor

Camshaft position (CMP) sensor

The CMP sensor is used in conjunction with the CKP sensor to inform the ECM of the position of the engine in the 4 stroke cycle. Using the CKP sensor alone, the ECM is unable to determine whether a cylinder is on its compression stroke or exhaust stroke.

The sensor uses the principle of magnetic induction to generate the signal. The cam wheel has four gaps, one smaller than the others, which pass in close proximity to the CMP sensor as the camshaft rotates. The lobes disturb the magnetic field of the sensor and induce a voltage in the sensor coil.

In the event of a sensor failure, the ECM will continue to operate normal ignition timing and sequential fuel injection using the CKP sensor signal. The sequential fuel injection may be 180° out of phase. Engine knock detection and correction will be disabled.

Inlet air temperature (IAT) sensor

The basis of the IAT sensor is a temperature dependent resistive metal strip. The resistance of the metal strip varies considerably with temperature. When an inlet temperature of 55°C or higher is detected, the ECM retards the ignition timing . If the sensor fails, the ECM assumes an inlet temperature or 50°C.

Knock sensor

The knock sensor is a piezo-electronic accelerometer, which produces an electronic signal related to the vibration of the engine. A knock sensor is located in each bank of cylinders. The signal from each knock sensor is transmitted to the ECM. The ECM is able to filter out normal engine vibrations and detect vibrations induced by engine knock.