Caterpiller C13 with DPF

Runfast. Cat doesn't support the emissions system that never did work.
Moisheh

That two year time from no dpf to def is fraught with i$$ues...Google, then run.

CAT RV Hotline 877 777-3126

Call with the engine number and they have the Mx history of any service done by an authorized CAT shop.

I would look for the door and run. At the very least get the engine serial number and find a Cat distributor or a truck dealer that is authorized Cat service dealer (most new truck dealers are) and have them check the repair history. 2009 was the last year Cat made a EPA certified on highway engine and they only made a DPF engine from 2007 to 2009 so the knowledge base for this engine is not very deep.