Knock Sensor (KS): Notes
WARNING: This page is about a different car, the 2005 Hyundai Accent and 2004 Hyundai Accent. However, it is still accessible from the selected car via links, so may be relevant.
The knock sensor is attached to the side of the cylinder block to sense engine knocking. A knocking vibration from the cylinder block is applied as pressure to the piezoelectric element. This vibrational pressure is then converted into a voltage signal which is relayed to the ECM. If engine knocking occurs, ignition timing is retarded to suppress it.