Knock Sensor 2 Circuit Malfunction (Bank 2)
The knock sensor on Bank 2 isn't communicating properly with your engine computer. It's like a smoke detector that isn't sending signals when it detects smoke—the engine can't tell if detonation is happening.
The ECU monitors the knock sensor's voltage signal for vibrations indicating pre-ignition (detonation). It expects a specific frequency range and amplitude from the sensor circuit. If the signal is absent, shorted, or out of range, the fault is triggered.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Knock Sensor Signal Voltage | 0.5–4.5V AC oscillation with knock detection | No signal, continuous 0V, or >5V |
| Signal Frequency Range | 4–10 kHz during knock events | Signal absent or outside expected range |
Code P0331 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0331 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.