Knock Sensor: Description and Operation

This sensor uses a piezo-electric sensing element to detect knock which may occur under acceleration at critical conditions. Should detonation be present the ECM will retard the ignition timing of individual cylinders.





Two knock sensors are installed to the cylinder block on the inboard side of each cylinder bank. The flying lead of each sensor is secured to a bracket on (or near to, depending on the model) the thermostat housing.
These piezo-electric sensors provide inputs to the ECM to indicate the detection and location of detonation during combustion.