Engine

P0331 — Knock Sensor 2 Circuit Range/Performance (Bank 2)

Severity: medium Drive with care, to a shop

What P0331 means

A knock sensor is a piezoelectric sensor bolted to the engine block that picks up vibrations from combustion knock. The engine computer uses it to retard ignition timing and protect the engine. P0331 sets when the signal from knock sensor 2 on bank 2 is outside the expected range or does not match normal engine noise.

Symptoms

  • Check Engine light on
  • Pinging or knocking under load
  • Reduced power and sluggish acceleration
  • Worse fuel economy
  • Rough idle or hesitation

Possible causes

  1. Failed knock sensor 2
  2. Open, shorted, or corroded wiring or connector
  3. Sensor loose, over-tightened, or poorly seated on the block
  4. Actual knock from low-octane fuel, carbon buildup, or overheating
  5. Internal engine mechanical noise (bearings, pistons)
  6. Rarely, a faulty ECU

How to diagnose

  1. Scan all codes and review freeze frame data for related ignition or fuel trim faults
  2. Inspect the sensor connector and harness for chafing, oil, corrosion, or heat damage
  3. Check the sensor mounting and torque to spec, and make sure the mounting surface is clean
  4. Measure sensor resistance and reference voltage per the vehicle wiring diagram
  5. Test the wiring to the ECU for opens and shorts to ground or power
  6. Compare the signal on a scope or scan tool while lightly tapping near the sensor
  7. Rule out real knock: fuel quality, spark plugs, engine temperature, mechanical noise
  8. If wiring and sensor test good, evaluate the ECU

Common fixes

  • Retorque the sensor and clean the mounting surface
  • Replace knock sensor 2
  • Repair the harness or replace the connector
  • Fix the cause of real knock (fuel, plugs, overheating, mechanical)
  • ECU repair, reflash, or replacement as a last resort

Questions and answers

What does P0331 mean?

The ECU sees the bank 2 knock sensor 2 signal outside its expected range. The cause may be the sensor, wiring, mounting, or real engine knock.

Can I drive with P0331?

Briefly and with light loads. The engine runs in a protective mode, and real knock could cause serious damage, so diagnose it soon.

How do I tell a bad sensor from bad wiring?

Inspect the connector and test the circuit to the ECU. If the wiring is good but the sensor's resistance or signal is out of spec, replace the sensor.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.