How does a knock sensor retard the timing?

•many EFI engines have knock sensor.the knock sensor may be mounted in the block cylinder head or intake manifold.

•A piezoelectric sensing element is mounted in the knock sensor and the resistor is connected parallel to the sensing elements. when the engine detonates, a vibration occurs in the engine.

•The piezoelectric sensing element changes the vibration into an analog voltage and this signal is sent to the knock sensor module.

•The knock sensor module changes the AC voltage signal into a digital voltage and sends this signal to the ECU. When the ECU receives this signal, it reduces the spark advance to prevent detonation.

•Reference book: Automotive technology