P1331

What it means

P1331 on a Volkswagen means the engine control unit has reached the limit of how far it can retard the ignition on cylinder 7 to control knock. It has pulled timing back as far as it is allowed and still detects knock or combustion noise on that cylinder. This code only applies to engines with at least seven cylinders, such as V8 and V10 units, so the exact cylinder position depends on the engine.

Symptoms

• Engine management light on
• Reduced power and flat acceleration, especially under load
• Rough or uneven running
• Audible pinging or rattling on acceleration
• Poorer fuel economy

Possible causes

• Poor quality or incorrect fuel (low octane) causing real combustion knocklikely
• Faulty knock sensor or damaged sensor wiring or connector serving cylinder 7likely
• Knock sensor mounting loose or incorrectly torqued, causing false knock signalspossible
• Worn or incorrect spark plug or weak ignition coil on cylinder 7 causing poor combustionpossible
• Carbon build-up, fuel injector fault or lean mixture on cylinder 7possible
• Mechanical noise from the engine, such as piston slap, bearing wear or loose components, mistaken for knockrare

How to diagnose

1. Read all stored codes and freeze frame data, noting engine load, speed and temperature when the fault set, and check for misfire or other knock codes
2. Ask what fuel has been used recently and consider whether a tank of low octane fuel could explain it
3. Inspect the knock sensor wiring and connector for chafing, oil contamination, corrosion or heat damage
4. Check the knock sensor mounting and tightening torque to the manufacturer specification
5. Inspect the spark plug and ignition coil on cylinder 7 and compare with the other cylinders
6. Using live data, compare knock retard values across cylinders to see if cylinder 7 stands out
7. Check injector operation, fuel trims and signs of a lean condition on the affected bank
8. Listen for genuine mechanical noise with a stethoscope if the electrical checks are clear

How to fix

• Drain and replace poor quality fuel with the correct grade, then clear the code and retest
• Repair or replace damaged knock sensor wiring or connectors
• Replace the faulty knock sensor and fit it to the correct torque
• Replace worn spark plugs or a failing ignition coil on cylinder 7
• Correct the lean or injector fault, and clean carbon deposits if confirmed as the cause
• Repair any confirmed mechanical engine fault found to be causing the noise

Can I keep driving?

Nearby codes

• P1330VolkswagenCylinder 6 Knock Control Limit Attained
• P1332VolkswagenCylinder 8 Knock Control Limit Attained