Prostar ISX issue

Hi there,
This question is directed to those with good knowledge of Cummins ISX. Dealing with God #### very frustrating code (Cummins 3225 Aftertreatment purge air actuator - mechanical system not responding or out of adjustment ) or (International 3490 fmi 7, same description )
Truck has 300k mostly original parts wise, except for new Aftertreatment air purge valve and aftertreatment fuel doser valve/injector.
Truck does regen fine, heats up to 1040 degrees and completes the regen. When code is deleted and we run the regen everything looks fine until ECM switches from aftertreatment injector status Not dosing to Dosing. It throws Cel immediately upon switch sequence.
What else can be checked though? Shop reported purple air line not leaking, I'm currently out of ideas so if you know something more and don't mind to share, I'd appreciate your help.

 

Code is being thrown immediately after ECM requests switch to "Dosing fuel" during parked regen. Regen is successful but code stays on

 

Thank you QUALITYTRUCK, it seems like fairly easy swap. Do you have any helpful pointers you can share with me.
Jacob

 

Yes I've done manifold replacement also hp turbo and fuel pump on Maxxforce lol.
I still have that prostar with maxxforce and it keeps on running which is great btw. Thank you again, will come back in a few days to report findings. Have a great day and stay safe

 

Hats of to you my friend, it was indeed aftertreatment fuel shut off solenoid. You were right too on "having small hands will be helpful" which I don't and I'm 6', that didn't help either. But I got it done. What made it easier to remove atsv was to remove mounting bolts on air purge valve so you're able to maneuver both atsv and apv.
Tools needed:
19mm ratcheting wrench open-close ended
17mm ratcheting wrench open-close ended
14mm ratcheting wrench open-close ended
10mm ratcheting wrench open-close ended
10mm socket, extension and ratchet
Zip tie cutter
Small hands
Small body frame
Patience
2 hours if never done it before
Thank you QUALITYTRUCK