Knock sensor (Mitsubishi Matrix)

The knock sensor is mounted on the cylinder block. The sensor senses the vibrations of the cylinder block walls that occur during detonation. The piezoelectric element of the sensor converts this vibration pressure into a voltage signal. The engine control unit uses this signal to suppress detonation by shifting the ignition timing toward retardation.

Conditions for storing fault codes

The ECU stores a fault code (the engine management system malfunction indicator lamp does not come on) if the knock sensor signal voltage drops below 650 mV for 4 s in two driving cycles under the following conditions:

• the starter does not work;
• crankshaft speed above 3000 min⁻¹;
• coolant temperature above 40°C;
• engine load is greater than 2.5 ms.

The output of this code indicates that the ECU has detected unusual vibration based on signals from the knock sensor during normal engine operation.