I have a Ford F-150 xlt 4.6 with a p0401 code
Have have checked the intake ports on the egr and they werent clogged,changed egr,egr vacum solenoid,checked hoses,changed Dpfe sensor, exhaust pipe to egr and still keep getting the code.
Cars & Trucks - Ford - F-150
Answers & Comments
Code p 0401 refers to exhaust gas recirculation (EGR) system---insufficient flow detected==== causes ---hose leak/blockage, basic setting not carried our (if applicable)---wiring---EGR valve ---EGR solenoid ---ECM
when you have done everything make sure that you use a scan tool to reset the ECM
Items that you haven't mentioned are wiring and substituting the ecm with a known operational one
bad wiring and connections / ground , broken in side the insulation may cause the problem as well