P0331

What it means

P0331 is the generic code for a range or performance problem in the circuit of knock sensor B, which is normally the sensor on bank 2 of the engine. The engine control unit saw a signal from the sensor that was outside the expected range or did not behave plausibly for the engine speed and load. Sensor layout and the exact test used vary by engine, so check the manufacturer's data for your model.

Symptoms

• Engine warning light on
• Reduced power or sluggish acceleration as the ignition timing is held back
• Poorer fuel economy
• Pinking or rattling under load if the knock is real and not detected
• Rough running or hesitation in some cases

Possible causes

• Damaged, chafed or corroded wiring to the knock sensor, or a poor connectorlikely
• Faulty knock sensor giving a weak, noisy or out-of-range signallikely
• Knock sensor loose or tightened to the wrong torque, so it does not pick up block vibration properlypossible
• Real engine mechanical noise, such as worn bearings, piston slap or loose components, being read as knockpossible
• Oil or coolant contamination of the sensor connector or harness (for example from a leaking gasket)possible
• Fault in the engine control unit or its sensor input circuitrare
• Outdated control unit software where the manufacturer has issued a known fix for this coderare

How to diagnose

1. Read all stored codes and the freeze frame data, noting engine speed, load and temperature when the code set
2. Check for related codes, and look up the manufacturer's data for the sensor location and the bank 2 definition on this engine
3. Visually inspect the knock sensor wiring and connector for chafing, heat damage, oil contamination, corrosion and bent or pushed-back pins
4. Check the sensor is fitted correctly and tightened to the specified torque, and that it is not cracked
5. Measure the sensor circuit for continuity, short to earth, short to voltage and resistance against the manufacturer's specification
6. Watch the live knock sensor signal on a scan tool at idle and while the engine is gently revved, and compare it with a known good sensor or the specification
7. Listen for abnormal engine noise with a stethoscope to rule out a genuine mechanical fault
8. Check for any applicable software updates or technical bulletins for the vehicle

How to fix

• Repair or replace damaged wiring and clean or replace faulty connectors
• Replace the knock sensor if it fails electrical or signal checks, fitting it to the correct torque
• Refit or correct the mounting of a loose sensor, using a clean seating surface
• Fix any oil or coolant leak that is contaminating the harness, and replace the affected harness section
• Repair the underlying mechanical fault if the engine is making genuine abnormal noise
• Update the control unit software only where the manufacturer lists it as a fix for this code, or replace the unit if it is proven faulty

Can I keep driving?

Nearby codes

• P0330GenericKnock/Combustion Vibration Sensor B Circuit
• P0332GenericKnock/Combustion Vibration Sensor B Circuit Low