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P0401

Exhaust gas recirculation flow insufficient detected

The ECU has detected less EGR flow than expected.

What this code means

The ECU has detected less EGR flow than expected.

Possible causes

  • Blocked EGR passages
  • Sticking or failed EGR valve
  • Vacuum or actuator fault
  • EGR pressure or position sensor fault
  • Wiring problem

Common symptoms

  • Check engine light
  • Possible hesitation
  • Rough running in some vehicles
  • Increased combustion temperature or emissions

Checks to make

  1. Check for related EGR codes
  2. Inspect accessible EGR hoses and connectors
  3. Review commanded versus actual EGR data
  4. Check for carbon blockage in the EGR path according to manufacturer procedure

Safety

  • EGR and exhaust components can be very hot. Allow the engine to cool before inspection.

Model notes

EGR system design differs widely by vehicle.