Knock Sensor
WARNING: This page is about a different car, the 1993 Toyota MR2. However, it is still accessible from the selected car via links, so may be relevant.
Knock sensor monitors ignition knock conditions and delivers an input signal to KNK or KNK1 and KNK2 terminals of Engine Control Module (ECM). The ECM uses input signal to determine ignition timing (spark advance) and control fuel injection system.