Knock Sensor (7/24, 7/472-473) [2019-2021, B4204T23; B4204T27 | 2019-2022, B4204T28 | 2020-2022, B4204T39 | 2021, B420T | 2021-2022, B420T2]: Description

The knock sensor monitors the vibrations in the engine block. The sensor converts mechanical vibration from the engine block to an electronic signal that corresponds to the frequency and amplitude of the vibration. The sensor is made of a piezoelectric crystal. The Engine Control Module (ECM) registers the signal and can thereby determine whether the engine knocks or not.