The knock sensor is a piezoelectric accelerometer that acts as a microphone on the engine. It converts vibrations into alternating current (AC) signal. When the crystal inside the sensor is vibrated, it produces an AC voltage.

The greater the vibration or shock, the higher the voltage and frequency. In this video we discuss how a knock sensor can fail, testing and diagnostics.

The greater the vibration or shock, the higher the voltage and frequency. This video was created by Babcox Media and Tech Minute and is sponsored by NGK Spark Plugs.