Circuit Description
WARNING: This page is about a different car, the 2003 Toyota RAV4. However, it is still accessible from the selected car via links, so may be relevant.
The knock sensor is fitted on the cylinder block to detect the engine knocking. The sensor contains a piezoelectric element which generates a voltage when it becomes deformed. This occurs when the cylinder block vibrates due to the knocking. If the engine knocking occurs, the ignition timing is delayed to suppress it.