2010 Cummins isx 2637 code

Any Cummins experts on here? Looking at a truck that has a 2010 isx, no dash lights on but scanner is showing
2637; Aftertreatment 1 Diesel Oxidation Catalyst (DOC) face plugged - root cause unknown

Anyone know what it could be? Truck has over 700k miles, and in the spaceship (exhaust stack) looks like part of it has been replaced, possibly the filter? Not really sure though.

wondering if a hard forced regen from the computer would clear it up?

 

Anyone?

 

not sure how long the light has been active, the truck has been used very little in the last year ( since its replacement came in)
It’s a kenworth w900
The dpf is in the stack on the back of the truck. Truck usually hauls at 80-90k but does idle a lot (pump offs to unload)
I am looking at buying the truck ( very cheap) but am concerned this could be a bigger issue.
tried to do a forced regeneration with a snap on scanner; wouldn’t not start it, kept saying issue with ecu preventing regen from start. the soot level did say normal but still should have started. Truck runs fine otherwise

 

I do not believe that it is a carb retrofit, truck is a 2010, came from New Jersey. See attached pic of stack

 

No def, only dpf

 

It does lots of idling… I haven’t inspected anything, most of the trucks the company runs are pre def/dpf or 2018 and older. I am trying to research what will need to be done to clear the code, from what I gather first thing is to take apart the doc to inspect? Where is the 7th injector?