A fully functioning knock sensor is essential for maximum performance. It "listens" for engine knock often due to poor quality fuel. When it detects a "spark knock", it sends a signal to the ECM and an ignition timing correction is made to burn the fuel more efficiently. With the aid of the 1984-1996 Corvette Knock Sensor Tool and a digital voltmeter, you can easily test the knock sensor for peak performance. Instructions included.