Circuit/System Description

The knock sensor system enables the engine control module (ECM) to control the ignition timing for the best possible performance, while protecting the engine from potentially damaging levels of detonation. The sensors are located below each cylinder head on the engine block. The knock sensor produces an AC voltage signal that varies depending on the vibration level during engine operation. The ECM adjusts the spark timing based on the amplitude and the frequency of the knock sensor signal. The ECM receives the knock sensor signal through 2 isolated signal circuits. The ECM learns a minimum knock sensor noise level at idle and uses calibrated values for the rest of the RPM range. The ECM should monitor a normal knock sensor signal within the noise channel.