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P0401 Powertrain

Exhaust Gas Recirculation Flow Insufficient Detected

When the ECU commands EGR open, the actual flow measured by the DPFE sensor or the resulting MAP/MAF change is below threshold. By far the most common cause is a carboned-up EGR valve or blocked intake passages.

Affected components

  • Egr valve
  • Egr passages
  • Dpfe sensor

Common causes

  • High likelihood: EGR valve clogged or stuck closed
  • High likelihood: Intake EGR passages blocked with carbon
  • Medium likelihood: Vacuum line to EGR (vacuum-actuated valves) cracked

Diagnostic notes

  • The malfunction indicator lamp may illuminate
  • This code can affect emissions
  • A drive cycle may be required after repair

Sources

Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.

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