What is the purpose of a car knock sensor?

[Delaney]

The purpose of a car knock sensor is to detect engine knock and prevent the occurrence of knock phenomena. The symptoms of a damaged knock sensor include: 1. Reduced engine power accompanied by knocking sounds from the engine; 2. Potential damage to engine pistons and cylinder blocks, failure to detect engine detonation signals, and inability to automatically retard ignition timing. The working principle of a knock sensor is that when vibration or knocking occurs, it generates a small voltage peak. The more severe the knocking or vibration, the larger the main peak voltage produced by the knock sensor. A certain frequency indicates knock or detonation, and when the control unit receives this frequency, the ECU readjusts the ignition timing to prevent further knocking.