Knock Sensor Signals

There are 2 knock sensors located on engine block under intake manifold assembly. See Figure . The knock sensors are 2 piezoelectric solid noise sensors. Piezo effect is a voltage generated by pressure on a fixed ceramic. Vibration on engine block is transmitted onto each knock sensor. Each knock sensor converts engine block vibration to an AC voltage signal. The AC voltage signal is sent through a shielded wire to engine control module. The engine control module uses knock sensor signal to adjust ignition timing as necessary to prevent ignition spark knock.