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DTC P0401: Exhaust Gas RECIRCULATION (EGR) Flow Insufficient Detected

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P0401 - EXHAUST GAS RECIRCULATION (EGR) FLOW INSUFFICIENT DETECTED

Description:  The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the differential pressure feedback EGR (DPFEGR) sensor indicates that EGR flow is less than the desired minimum.
Possible Causes: 
  • Vacuum supply
  • EGR valve stuck closed
  • EGR valve leaks vacuum
  • EGR flow path restricted
  • EGRVR circuit shorted to voltage
  • VREF open to DPFEGR sensor
  • DPFEGR sensor downstream hose is off or plugged
  • EGRVR circuit open to the PCM
  • VPWR open to EGRVR solenoid
  • DPFEGR sensor hoses are both off
  • DPFEGR sensor hoses are reversed
  • Damaged EGR orifice tube
  • Damaged EGRVR solenoid
Diagnostic Aids:  Carry out the key on engine running (KOER) self-test and look for DTC P1408 as an indication of a hard fault. If DTC P1408 is not present, look for contamination, restrictions, leaks, and intermittent concerns.
Application  Key On Engine Off  Key On Engine Running  Continuous Memory 
Vehicles with an EGR system module (ESM) - - GO to Pinpoint Test HH .
All others - - GO to Pinpoint Test HE .
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