Just the Facts: Don’t Get PO’ed with PO401 Codes Ford P0401 Issues The Ford EGR Pressure Feedback system is known for persistent P0401 EGR low flow code issues. Bear in mind, low flow can be caused by several issues. The most common issue is the failure of the EGR Pressure Feedback sensor commonly known as the DPFE sensor. If the diaphragm in the sensor becomes weak or the sensor is contaminated with moisture it can fail to supply the computer with the correct reference voltage. When this occurs, the computer increases the vacuum supply to the EGR valve causing the vehicle to run poorly. When the low flow signal is unable to be corrected by the computer’s adjustment, then the computer sets a P0401 code for EGR flow. The other parts that commonly get overlooked are the EGR Valve Regulator (EVR), which is cataloged as an EGR control solenoid, the DPFE hoses, and carbon build-up inside the EGR system. The EVR is responsible for supplying the proper vacuum to the EGR valve. Any resistance in this control circuit or failure of the EVR can cause a P0401 code. The original DPFE hoses are a special high-temperature hose. These hoses can crack or collapse internally over time due to intense thermal cycling that takes place within the EGR system. To prevent a reoccurrence of the P0401 code, Standard recommends inspecting and replacing if necessary, the EVR and DPFE hoses when replacing the DPFE sensor. To further guard against a P0401 code, a de-carbonization treatment of the EGR system should be performed. View our 21st Century Tune-Up® video video Back to Just the Facts