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Home >> Toyota >> 2012 >> Prius Three >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System (Except Plug-In) (Diagnostic Codes (P0010-P043F)) >> SFI System >> DTC P0401: Exhaust Gas Recirculation Flow Insufficient Detected >> Description
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DTC P0401: Exhaust Gas Recirculation Flow Insufficient Detected: Description

Based on the driving conditions, the ECM regulates the volume of exhaust gas that is recirculated to the engine's combustion chambers and thus lowers the combustion temperature to reduce NOx emissions. The ECM monitors signals such as engine speed, coolant temperature, electric load, and vehicle speed. When the EGR permission conditions are fulfilled, the ECM controls the opening of the EGR valve linearly through signals to the EGR step motor.

DTC No. DTC Detection Condition Trouble Area
P0401 Change in intake manifold pressure is small when the EGR valve is opened and closed during idle fuel cut operation.
(2 trip detection logic)
  • EGR valve assembly
  • EGR passage
  • EGR pipe with cooler sub-assembly
  • Manifold absolute pressure sensor
  • ECM