SPN 4364 FMI 18?

[Billdozer2]

Hey guys, I got a check engine light on and curious if anyone has seen this fault before.

Fault is SPN 4364 FMI 18 - Aftertreatment SCR Catalyst Conversion Efficiency - Data Valid but Below Normal Operating Range - Moderately Severe Level.

I have access to Quickserve and Insite. According to the diagnostic tree on Quickserve, first step is to check for other codes active or inactive. There are no other codes in the system.

Truck is a 2013 Volvo 670 ISX 2250 (400ST)<----I know. It's a used big name company truck. Just under 370,000 miles.

Truck is stock and runs fine. Boost is normal. All temps are normal. Fuel mileage is normal.

I haven't checked anything else out yet. Just curious if anyone has seen this before and could give me a point in the right direction to cut down on diagnosing time.

Hopefully this is the first and last time I have to deal with after treatment issues, as I plan on going Plan C but I do not have anywhere to do it right now.

Thanks guys