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Exhaust gas recirculation (EGR)

P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient Detected

During the EGR monitor the ECU commands the EGR valve open and checks for the expected change in intake airflow, manifold pressure or temperature. P0401 is set when the detected EGR flow is lower than expected.

Common causes

  • EGR valve, cooler or passages clogged with carbon deposits
  • EGR valve stuck closed or not opening fully
  • Faulty EGR position sensor or flow feedback signal
  • Restricted EGR cooler
  • Wiring, vacuum hose or control solenoid faults

Typical symptoms

  • Check engine light (MIL) on
  • Higher combustion temperatures and possible knocking on petrol engines
  • Increased NOx emissions and possible emissions test failure
  • Reduced power on some diesel vehicles

P0401 and NuoVolta

When the EGR valve has been removed or blanked for off-road or motorsport use, where permitted by law, the NuoVolta EGR Removal solution adjusts the ECU calibration and the DTC removal feature can disable P0401. If the system is still fitted, clean or replace the clogged components first.

EGR Removal Available for 256 ECUs

Related codes

P0400Exhaust Gas Recirculation (EGR) Flow Malfunction P0402Exhaust Gas Recirculation (EGR) Flow Excessive Detected P0403Exhaust Gas Recirculation (EGR) Control Circuit Malfunction P0404Exhaust Gas Recirculation (EGR) Circuit Range/Performance P0405Exhaust Gas Recirculation (EGR) Sensor A Circuit Low P0406Exhaust Gas Recirculation (EGR) Sensor A Circuit High

Diagnose and repair real faults first. Removing or disabling emission systems is only permitted where allowed by law, for example for off-road or motorsport use.