OBD Code P0331: Knock Sensor 2 Circuit Malfunction (Bank 2)

Q: What does OBD code P0331 mean?

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.

Q: What are the symptoms of fault code P0331?

Check Engine Light illuminated, Engine pinging or knocking under load, Reduced fuel economy and performance

💬

What This Actually Means

In plain language — no jargon

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.

⚡

Symptoms You May Notice

3 known symptoms for this code

Check Engine Light illuminated

Engine pinging or knocking under load

Reduced fuel economy and performance

🔬

Embedded Systems Insight

What the ECU/ECM is actually computing

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.

Voltage & Parameter Thresholds

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

🔧

Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex

1

Knock sensor connector

Inspect and reseat the connector on Bank 2 knock sensor for corrosion or loose pins.

2

Knock Sensor (Bank 2)

Replace the knock sensor on Bank 2 cylinder head if connector is secure but signal persists.

3

Knock sensor wiring harness

Check harness from sensor to ECU for cuts, pinches, or damaged insulation causing shorts.