Sensor, Knock: Description
WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
The knock sensor is the piezoelectric type and is fitted on the crankcase to detect the intensity of the vibrations caused by detonation in the combustion chambers. The phenomenon produces a mechanical repercussion on a piezoelectric crystal that sends a signal to the Powertrain Control Module (PCM) and, on the basis of this signal, the PCM reduces the ignition advance until the phenomenon disappears. The advance is gradually restored to the basic value.