Screwed onto the cylinder block of the engine, usually below the intake manifold, knock sensors detect if the outbreak of the mixture in the cylinders of the engine occurs incorrectly - that is, in detonation conditions.

Detonation can be caused by excessive pressure/temperature or the use of a fuel with an inappropriate octane rating and can lead to a deterioration of engine performance and serious physical damage to the cylinders.

Electronic control unit determines the engine cylinder where the detonation occurred, through the signals emitted by the knock sensors, and reacts by reducing the pressure in the cylinder or reducing speed and combustion temperature using a variation of the mixture enrichment.