Fault code P0401 and 14A700

[200kjustrunin]

EML fault code P0401 and 14A700​

Indy identified a failed EGR valve on my E350 2011, changed valve but same fault. icarsoft shows EGR position as 1.4 % and it doesn't move as you rev to limp mode max at 2800rpm. EGR position changes when EGR valve operated manually. Does anyone know what the ECU monitors to control the EGR valve?

 

[Supernoodle]

I guess the other thread with P0501 in the title was an error. Report it so it gets deleted.

EGR is controlled to achieve a desired mass air flow, as measured by the MAF sensor. Insufficient flow detected suggests for the given valve opening, the mass flow was too high (EGR reduces air flow).
Negative contol deviation would mean valve is open more than expected.
They both suggest EGR is working but there's either insufficient gas flow (just like P0401 says), or the MAF values are wrong. But if the latter you'd expect other MAF errors.
Check the path between valve and exhaust, including the cooler.

Whilst you have fault, EGR is disabled so it won't move.

 

[200kjustrunin]

How would other MAF errors manifest? Another thread suggested loss of throttle body feedback could also attribute to these codes. Have ordered both and a EGR exhaust pressure sensor for good measure.

 

[Supernoodle]

A fault with mass air flow in the description, it has it's own plausability checks.

Throttle shouldn't be doing anything during normal engine running. It will be fully open.

 

[200kjustrunin]

Checked flow to the EGR and from the EGR via the cooler and flows look fine. Have checked MAF sensors and compared with each other, reading are the same but negative readings at idle! Swirl flap motor changed and manifolds refurbished, throttle body, EGR valve, exhaust back pressure and MAP (inlet) sensors changed, fault persists both 14A700 and P0402 return even at idle after a few seconds of being cleared! I'm stumped, only other item I've not checked is the turbo actuator, just need to find a wiring diagram so I can check live values.

 

[Supernoodle]

Negative says the air mass adaption has a negative offset. Run the change air filter routine to 0 the offset.

 

[200kjustrunin]

Negative says the air mass adaption has a negative offset. Run the change air filter routine to 0 the offset.

Thanks, will try and find some one with a scanner better than mine who can do the adaption. Explains why MAF figure is minus at tick over but jumps to 250 mg /Hub when i disconnect the boost pipe in front of the throttle body and can clear codes.

 

[200kjustrunin]

Update RH MAF was the cause, no specific fault code tondonwith MAF but changed MAF and all DTCs cleared.