Knock Sensor
WARNING: This page is about a different car, the 1995 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.
Knock sensors No. 1 and 2 monitor ignition knock conditions and deliver input signals to KNKR and KNKL terminals of Engine Control Module (ECM). The ECM uses input signal to determine ignition timing (spark advance) and control fuel injection system.