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P0333 Generic (SAE)

Knock Sensor 2 Circuit High Input (Bank 2)

Updated 2026-10-02 · Ignition system & misfires

Severity
Medium
Typical repair cost
50 – 450 EUR
System
Powertrain

What it means

The ECM sees a voltage on the bank 2 knock sensor circuit that is above the acceptable window, most often the full bias voltage because the circuit is open. The ECM cannot trust knock detection on bank 2 and applies a fixed timing retard, which costs power and fuel economy until the fault is repaired.

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Symptoms

  • Check engine light on
  • Flat feeling at mid-range and full throttle
  • Fuel consumption up by several percent
  • Possible knock audible from one side of the engine
  • No drivability change in mild driving on some vehicles

Common causes

  1. Open circuit: broken wire, backed-out terminal or unplugged connector at the bank 2 sensor
  2. Internally open knock sensor
  3. Signal wire shorted to a 5 V reference or 12 V supply
  4. Corroded connector pins creating very high resistance
  5. Wrong sensor fitted (resistor-biased type replaced with plain piezo or vice versa)
  6. ECM fault (rare)

How to diagnose

  1. With key on and sensor connected, backprobe the signal wire: on biased circuits expect about 2.5 V; a reading at full 5 V with the sensor plugged in means the sensor or its wiring is open.
  2. Unplug the sensor and check resistance between its pins; piezo sensors read roughly 4-6 MOhm, resistor-biased types read the specified value (often 100-600 kOhm). An infinite reading confirms an open sensor.
  3. Check the harness connector for pushed-back terminals and verify terminal tension with a test pin.
  4. Run a continuity test from the sensor connector to the ECM pin; under 1 ohm is good. Move the harness while measuring to catch intermittent breaks.
  5. Perform a tap test with an oscilloscope in AC mode: 100-500 mV spikes expected; nothing on bank 2 while bank 1 responds normally isolates the fault to that circuit.
  6. Verify the replacement part number if the sensor was recently changed; the wrong bias type produces a permanent high or low code.

Frequently asked questions

The code came back right after I replaced the sensor. Why?

Most likely the wiring is open or the wrong sensor type was fitted. Check for continuity to the ECM and compare the new part number with the original.

Does P0333 affect emissions?

Indirectly. Retarded timing raises exhaust temperature and fuel use, and some regions fail an inspection for any active emissions-related code.

Related codes

P0330P0331P0332P0328P0325

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