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P0401Cars & SUVs
Moderate

P0401 — EGR flow insufficient

The exhaust gas recirculation (EGR) system is not flowing enough gas. Common on diesel trucks and gas V6/V8s used for towing in cold climates.

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Likely causes

  • EGR valve clogged with soot and carbon
  • Blocked EGR passages or plugged EGR cooler
  • Faulty EGR position sensor or solenoid

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Recommended checks

  1. 1

    Clean or replace the EGR valve

  2. 2

    Clear the EGR passages and cooler

  3. 3

    Test the position sensor and control circuit

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Parts to replace