6.7 doesn't have a SCI, just CAN.
5 wires in the OBD II port:
+12 Batt
2x grounds
CAN +
CAN -
The CAN BUS goes through the TIPM, ECM, and PCM in the truck. The TIPM is basically a really expensive fuse box that is controlled by the CAN.
I can get you any diagrams you need.
Tobin