Toyota 3 4 Knock Sensor Location . Here is another for your enjoyment. The knock sensor is basically a microphone, set to respond to the sound frequencies of engine The knock sensor now exposed is the only wire going to the engine block in this location. Toyota Sienna Knock Sensor (Martha Myers) Your knock sensor is located under the air intake manifold. Not sure how true this is but thats all i have found. It has the Toyota trailer hitch and a what looks like the toyota wiring harness (or it was dealer installed when new). I asked a friend at a Toyota service dept. about it, and he says they have a special tool for the bolt. It is used to detect engine knock or detonation (there is a piezoelectric The signal from the knock sensor is sent to the PCM/ECM and that is used to control the engine's timing. Toyota 4Runner 1984 to 1995 How to Replace Knock Sensor ... Knock senso...