P0401 diagnostic help

[ZR36]

Hey all
Having some issues with the egr code P0401.
It's an MY13 Audi Q3 2.0TDi
100,000km
I had only owed the car for about 300km or one day before the first check engine light came on.
Since then I have had it to a mechanic and they cleaned out the intake manifolds throttle body and egr pipes over night. But the P0401 code came back after only a few km. So I took it straight back there the same day.
He was sure that a clean would fix the problem as he called Audi for a replacement egr valve and they said they have never sold one......he also showed me before and after, the before was unbelievable was almost 50% restricted and the after photos were clean as a whistle. He also showed me the amount of gunk he got out, you could fill a take away container.
So I left it with him for the remainder of the day. I told him to check the DPFE so he swapped that out (with one from a VWEos) but no luck the P0401 code has returned. Again only few km went by before it threw the code.

Can anyone comment on what to do next?
Has anyone had to replace the egr valve?

[jets]

Is this link to the Ross-Tech site any help for you?

16785/P0401/001025 - Ross-Tech Wiki

[ZR36]

Definitely not. It's very generic page And it doesn't go into specifics and diagnosis like other pages do. Such as what range the readings should be for certain parameters under normal functioning operations....
I have already checked the 3 solutions it specifies and need targeted information to this vehicle...

1. Egr system has already been cleaned (and DPFE module replaced)
2. The valve is working according to the live 'erg_error%' on the scan tool. ie its opening and closing during running
3. It's not the wireing as this does not trigger the P0401 code. (this is p0409)

[Transporter]

Definitely not. It's very generic page And it doesn't go into specifics and diagnosis like other pages do. Such as what range the readings should be for certain parameters under normal functioning operations....

Kind of they expect that the diesel mechanic knows the basics of the diesel engines emission systems.

[LukePolo]

First thing i'd check is to make sure the previous owners didn't EGR off the thing in the ECU software and then the person or dealer in between didn't reconnect all the sensors throwing odd values to the ECU.

I'd disconnect the EGR valve motor to see if the code remains or the drive of the vehicle actually changes.

Secondly i'd check to ensure the EGR bypass pipe isn't blocked or any of the rubber tubes that run to the sensors surround it or there isn't a leak with the gasket between cooler pipe/ bypass pipe and valve. All well and dandy to ensure that there is a free flowing EGR motor but what about the rest of the system?