The knock control system consists of the Knock Sensor, its connector, the wiring, and the PCM. The sensor is a device that is screwed directly into the engine block. Although the location may vary depending on the manufacturer, it is located on the sides of the block and in the coolant lines. For this reason, be careful when removing this sensor.
The Knock Sensor has a piezoelectric crystal inside. When it shakes or perceives vibrations produces an amount of voltage. Since the control circuit is a single wire to ground, the PCM (Powertrain Control Module) recognizes the voltage generated by the vibration as a detonation or ping of the engine. The level of voltage produced is highly dependent on the vibration level of the sensor crystal.
The Knock Sensor usually produces a small amount of voltage when the engine is running. This is because it is inevitable that the engine causes vibration, and as a result, amounts of sensor voltages. If the PCM detects an unexpected or out-of-range signal from the Knock Sensor, it will set the P0324 OBDII fault code.