I have an older wire list which cross references to older line numbers; I searched for IB37, IB46, and IB47.
It comes up with Cummins ECM "B" COMM - J1939data. IB46 is "+" and IB47 is "-" and IB37 is "Shield" for twisted pair cable. I have a second reader port under dash in my 2007 Allure.
Is it possible the "second" twisted pair (blue cable) is heading to a front reader port?
It is also possible something shorted in the twisted pair (they are teeny wires).
Can you remove the pin from the ECM connection and add a new wire and pin inside the connector? There are tools to remove pins from connectors - they are the most dainty mechanic tools I own, lol, next one is the old dental pics for Oring removal....
Hope this helps,
Towr: 2007 Country Coach Allure 470 - 37 Sunset Bay Cummins 400 ISL
Toad: 2016 F150 King Ranch - 3.5L EcoBoost 4x4 Supercrew (curb weight 4,775 lbs)
Toad: SOLD 2007 Jeep Grand Cherokee (yes, it has a Hemi) (curb weight 4,720 lbs)