I found this regarding resetting the "Service Required See Dealer Now"
My H&S Black Maxx will not turn off this warning by clearing DTCs.
This is what I found out about resetting the ECM:
1. Unhook both of your negative cables. Make sure when you lay them down, that they're not touching anything metal.
2. Unhook both of your positive cables. Lay them down so they don't touch anything metal.
(note: this is a good time to clean them up if they need it)
3. When you have all 4 unhooked, touch one pair of cables together (ie. driver's side pos. and neg.), then lay them back down...again making sure they don't touch metal. Do the same for the other side.
4. Reconnect your positive cables and tighten them.
5. Reconnect the negative cables and tighten them.
This process will reset the ECM. Learned that from a friend who is a dealer tech.
thread link OHC Service Required Reset - 6.7 Cummins Forum
Also regarding this just recently appearing, I think it has something to do with me disconnecting my negative cables to clean them over the weekend. I think that may have triggered this warning. It happened the first time I drove the truck after doing so.