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OBD code P0401

The EGR valve is not recirculating as much exhaust gas as the ECU expects.

Estimated severity
Medium
Common symptoms
  • Check engine light on
  • Hesitation at partial load in some cases
  • Possible slight power loss
  • More metallic or harsher combustion noise
Likely causes
  • EGR valve clogged with carbon buildup
  • Blocked recirculation passages
  • Faulty EGR actuator, vacuum or electric
  • EGR position sensor issue, if fitted
Recommended checks
  1. 1. Visually inspect the EGR valve and its connecting pipes.
  2. 2. Use a scanner to command the EGR and check its response.
  3. 3. Remove and clean the valve and passages if they are full of carbon.
  4. 4. If cleaning does not solve it, check the actuator and, if needed, replace the EGR valve.

What does code P0401 mean?

Code P0401 means the exhaust gas recirculation flow is lower than expected. It is often caused by carbon buildup in the EGR valve, blocked passages or a valve or actuator problem. It increases NOx emissions and can cause hesitation or harsher combustion noise.

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