Engine

P0333 — Knock Sensor 2 Circuit High Input (Bank 2)

Severity: medium Drive with care, to a shop

What P0333 means

The engine computer is reading a voltage from the Bank 2 knock sensor that is higher than expected. The knock sensor works like a microphone, picking up engine block vibration so the computer can detect detonation and pull back ignition timing. With a circuit fault, the computer cannot trust the signal and falls back on a protective strategy.

Symptoms

  • Check Engine Light on
  • Loss of power and sluggish acceleration
  • Worse fuel economy
  • Rough or uneven idle
  • Pinging or rattling under load (if real detonation is present)

Possible causes

  1. Failed knock sensor 2 (Bank 2)
  2. Damaged, corroded or chafed wiring or connector at the sensor
  3. Signal wire shorted to voltage
  4. Sensor installed or tightened incorrectly (wrong torque, dirty mounting surface, extra washer)
  5. Actual detonation from low-octane or poor fuel or a mechanical problem
  6. Faulty PCM (rare)

How to diagnose

  1. Scan all codes and freeze frame data and look for related ignition or fuel codes.
  2. Inspect the knock sensor connector and harness for corrosion, oil, rubbed insulation and heat damage.
  3. Check the sensor's mounting and torque; it must sit flat against the block with no spacer unless the maker specifies one.
  4. With a multimeter, check reference voltage and make sure the signal wire is not shorted to power or ground.
  5. Measure sensor resistance and compare it with the spec for your engine.
  6. Test the wire from the sensor to the PCM for opens and shorts.
  7. Watch the sensor signal on a scan tool while tapping near it; the reading should respond.
  8. Rule out real knock: fuel quality, spark plugs, engine temperature and carbon buildup.

Common fixes

  • Replace knock sensor 2 and tighten it to the factory torque
  • Repair or replace the damaged wiring or connector
  • Fix the cause of real detonation and use the correct octane fuel
  • Check, reflash or replace the PCM (last resort)

Questions and answers

What does P0333 mean?

The PCM sees too high a signal in the circuit of knock sensor 2 on Bank 2. The sensor itself or its wiring is the most common cause.

Can I drive with a P0333 code?

Briefly and gently, yes. But without proper knock control the engine can be damaged, so have it diagnosed soon.

Will clearing the P0333 code fix it?

Clearing only turns off the light for a while. If the fault is still there, the code returns and the engine keeps running with reduced timing.

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.