Knock Sensor (KS): Notes
WARNING: This page is about a different car, the 2004 Hyundai Santa Fe and 2003 Hyundai Santa Fe. However, it is still accessible from the selected car via links, so may be relevant.
The knock sensor is a piezoelectric device attached to the cylinder block that senses pressure from engine knocking conditions. This vibrational pressure is then converted into a voltage signal which is delivered as output. If engine knock occurs, ignition timing is retarded to suppress it.