I have a Mazda Tribute 2001 3.0 V6 engine. CEL came on so I had it checked by 3 different places. All come back with P0401 code. I first cleaned the EGR valve. My next step was to replace EGR valve, EGR control Solenoid. CEL did not reset so I replaced EGR Pressure Feedback Sensor. I have also cleaned the pipe leading to EGR valve. CEL is still not resetting and I need to pass inspection. What am I missing here.

 

DTC P0401
EGR flow insufficient detected


DETECTION CONDITION

• The PCM monitors EGR system during steady state driving conditions while the EGR is commanded on. If the signal from differential pressure feedback (D.P.F.) EGR sensor indicates that EGR flow is less than the desired minimum, the PCM determines EGR flow insufficient detected.

POSSIBLE CAUSE

• Vacuum hose malfunction (damaged, insufficient connected)

• EGR valve stuck close

• Vacuum leakage at EGR valve

• EGR flow pass restricted

• Short to power supply circuit in wiring EGR solenoid valve terminal 2 and PCM terminal 47 (R.H.D.) /E-27 (L.H.D.)

• Open circuit in wiring between EGR solenoid valve terminal 2 and PCM terminal 47 (R.H.D.) /E-27 (L.H.D.)

• Open circuit in wiring between EGR solenoid valve terminal 1 and main relay terminal 87

• Open circuit in wiring between D.P.F. EGR sensor terminal 1 and PCM terminal 90 (R.H.D.) /E-40 (L.H.D.)

• D.P.F. EGR sensor downstream hose off or plugged

• D.P.F. EGR sensor hoses both off

• D.P.F. EGR sensor hoses connected reverse

• EGR orifice tube damaged

• Damaged EGR solenoid valve

• Damaged PCM