Two codes gone, replaced by another !!!!!!

Well I have gotten rid of two codes by replacing the throttle pedal idle validation switch code gone and 5v supply elec fault code gone in the 2008 d13 only problem is I have a new one show up. The new code is Nox downstream scr catalyst out of calibration mid 128 pid 270 fmi 13. I am assuming this will be dealer only repair calibrating with laptop. Any one have that code before or know what it means? Getting very frustrated with volvo engine codes.

 

Yup took it for a 1/2 drive it was right up to temp. The code is not causing the check engine light to come on or de rate engine as far as I can tell but the code is in the diagnostic codes retrieved through cluster and was active.