Knock Sensor

The knock sensor is located on rear cylinder bank of engine block between cylinders 1 and 3 in upper crankcase. The knock sensor detects abnormal vibration (spark knock or detonation) in engine. The sensor produces an alternating current (AC) voltage which increases with severity of knock. The knock sensor id specifically "tuned" to engine based on frequency of vibration that engine creates when it knocks. The knock sensor for Northstar engine is tuned to 7000 Hertz. This signal is an input to PCM, which adjusts spark advance to reduce spark knock.