What does it mean?
The knock sensor (KS) is mounted in the engine and is used to detect spark knock. When there is spark knock or pinging, the sensor produces a voltage signal that is sent to PCM. The PCM will then retard ignition timing to protect the engine. Inside, the knock sensor is a piezoelectric crystal. This crystal is used to produce AC voltage under vibration. The knock sensor is a form of transducer, which is a device that converts changes in physical quantity into an electrical signal.
In other words, a knock sensor does not receive a reference voltage from the PCM – it creates its own. There are two basic types of knock sensors: the style used in older vehicles and the resonant design used in modern vehicles. Cross section of a typical knock sensor P0331 stands for knock sensor circuit performance. This means the PCM has detected a problem with the knock sensor or its circuit. Some vehicles may be equipped with two knock sensors.
Code P0331 pertains to the sensor on bank 2 (the opposite side of the engine where the #1 cylinder is located).