Knock Sensor

NOTE: Knock Sensor (KS) may also be referred to as knock sensor No. 1.

KS is located on side of the cylinder block. See Fig 1-Fig 7 . Manufacturer recommends removing knock sensor from cylinder block before testing. See appropriate N - REMOVE/INSTALL/OVERHAUL article.
Using ohmmeter, check that no continuity exists between electrical terminal on knock sensor and body of knock sensor. Replace knock sensor if continuity exists.

Fig 1: Locating Knock Sensor (Camry)