Knock Sensor [KS]
Knocking is a phenomenon characterized by undesirable vibration and noise that can cause engine damage. A knock sensor is mounted on the cylinder block and senses engine knocking. A knocking vibration from the cylinder block is applied as pressure to the piezoelectric element. A knock sensor sends sensor vibration when RPM rises or drops and generates voltages based on this vibration. The ECM controls the ignition timing based on the amplitude and frequency of the knock sensor Signal. For example, if engine knocking occurs, the ignition timing is retarded to prevent it. The knock sensor is attached to the cylinder block and senses engine knocking. The sensor contains a piezoelectric element that converts vibration (or noise) into voltage signal and sends this signal to ECM. With input signals from camshaft position and crankshaft position sensor, ECM can identify which cylinder is knocking. ECM filters vibrations and determines if the vibrations are knocking signal. The ECM uses this signal to suppress knocking by retarding ignition timing. The ECM will set a code (Malfunction Indicator Lamp will Not turn on) if during two driving cycles the Knock sensor's output voltage falls below minimum threshold. This code indicates an unexpected vibration is being read by the Knock sensor or ECM under normal engine operation.