SPN 520349 FMI 14

Very simple code very easy to diagnose. But only if you know what to do and how to do.
I love that forum giving me very good hints sometimes and try to giving some good advice to someone.
But so many false information flying around the internet. Soot sensor responsible is measuring soot level.
Not actual soot level in the dpf filter actual soot level what leaves the dpf filter.
Normally almost zero. If the soot sensor functioning correctly and soot sensor test pass with triple d software its simply as it
If the shop who cleaned the dpf maybe damaged one or two plugs a
end of the channels. Or your dpf canister have a crack.
No full of dpf canister.
No bad 7th injector
Nothing to do with scr functionality
You can drive the truck with dpf filter full and check engine light on with the code stating need dpf ash cleaning days weeks and months. This code never going to set . Never. Maybe give you driveability problems but not the code what you have.
Again this code only and only set if excessive soot passing over the dpf filter.
Unfortunately I can't fix it for you only hopping steer you to some good direction.