Engine

P033E — Knock Sensor 4 Circuit Intermittent (Bank 2)

Severity: medium Drive with care, to a shop

What P033E means

The engine control unit monitors knock sensors that listen for vibrations in the engine block, which reveal abnormal combustion. P033E is set when the signal from knock sensor 4 on Bank 2 drops out or goes out of range from time to time. The problem comes and goes rather than being constant.

Symptoms

  • Check Engine light on
  • Hesitation or reduced power
  • Rough or unstable idle
  • Poor fuel economy
  • Occasional stumbling under load

Possible causes

  1. Failed knock sensor 4
  2. Damaged or corroded sensor connector or terminals
  3. Chafed or broken wiring near the engine block
  4. Poor engine ground
  5. Loose sensor mounting or damaged mounting bore
  6. ECU fault (rare)

How to diagnose

  1. Scan all codes and freeze-frame data and look for other knock sensor codes
  2. Find knock sensor 4 using the wiring diagram for your specific engine
  3. Inspect the harness and connector for chafing, oil, corrosion and a loose fit
  4. Wiggle the harness with the engine running and watch for the code or live data changes
  5. Check the sensor torque and the condition of its mounting surface
  6. Test circuit resistance, continuity to the ECU and shorts to ground
  7. Check engine grounds and the reference voltage per the manufacturer's specs
  8. Suspect the ECU only after everything else checks out

Common fixes

  • Replace knock sensor 4
  • Repair the wiring or replace the connector
  • Clean and restore engine ground connections
  • Secure the harness and the sensor to the correct torque
  • Reflash or replace the ECU (last resort)

Questions and answers

What does P033E mean?

It means the signal from knock sensor 4 on Bank 2 is intermittent. The usual culprits are wiring, a connector or the sensor itself.

Can I drive with P033E?

For a short time, yes, but get it checked soon. The engine may run with reduced timing and lose power, and undetected knock raises the risk of engine damage.

Why does the code come and go?

Typically a poor contact or a cracked wire that acts up with vibration, heat or moisture. That is why wiggling the harness during diagnosis helps.

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.