robertwong,
What did you use to obtain the p246b code?
What resource did you use to interpret that code as meaning "diesel particulate filter regeneration"?
If your DPF is regenerating....that's good!
If it's not, and you have < 100 k miles on your Sprinter....my next stop would be an authorized Mercedes Benz
Sprinter dealer (a commercial dealer if you can find one).
Your DPF should be covered to 100k miles by your emissions warranty.
Roger
P.S. the code you are citing (p246b) is not a Mercedes Benz code, so if you decide to visit the dealer, it would be far better to simply say that
you have a Check Engine Light (CEL).
They will do a correct diagnosis using the MB SDS diagnostics, and it may prove to be something else entirely.
Oh, what engine oil have you been using and how much time does your Sprinter's engine spend @ > 2800 RPM.
Wrong oil, lot's of idling, lots of low RPM operation....and it could be your DPF is plugged.
Roger