Knock Sensor: Location and Testing

The knock sensor prevents the engine from self-destructing under certain operating conditions.
When the knock sensor is damaged or fails, engine power decreases.
The knock sensor can be tested with an oscilloscope (by monitoring its signal when struck) or with a professional multimeter: resistance, capacitance in NANOFARADS (nF) and signal voltage in millivolts AC (mV AC) should be measured.