help with data link adapters and codes

[Midland]

Update and more questions. And maybe information for the next victim of J1939 failures

So far no visually damage wires. Dash is still in, have not pulled all the wire loom from the chassis to engine harness, but it tests OK. Testing OK doesn't really mean anything since I can't find the ECM from the diagnostic plug. Basically, it can't be broken and OK at the same time. Pretty sure it is broken. Duh.

The ohm testing on the J1939 data link (at the diagnostic plug) would appear to pass with the key off, and fail with the key on. OFF gives a nice 59 ohms, with the key on, it fluctuates. Basically, where every I break the J1939 and test, I get around 59 ohms, unless I break it such that one of the terminating resistors is out of the loop, then I get around 118 ohm. So I started working down the data link under the seat to the sleeper and at one point thought I had found something. One plug was giving 51K ohms. However, after more digging, it appears that this data link is radio only. 51K ohms with the radio plugged into the harness, open circuit with the radio unplugged. 59 ohms when I test the other end of the plug going into the sleeper. Appears to go from the main radio to the sleeper radio, has two terminating resisters built into the plugs at the sleeper remote radio.

So, does anyone one know, did International (or anyone else for that matter) use multiple but separate data links? Oops, maybe answering my own question here, the wiring diagram shows the radio data links going back to the "Driver Display". Will have to verify that as that could be my broken link.

Also, went and found the two terminating resistors. One in the wire harness in front of the cab (right in front of the accelerator, the other on the left frame rail behind the transmission, right where the 1st U joint throws grease all over. The both look good, and if either is unplugged, I get approximated 118 ohms.

BUT, then I discovered another (yes, a third) terminating resistor on the bunk heater assembly. That data link appears to run parallel to the radio link, I have not confirmed for sure that they are indeed totally separate, but right now I think they are. That leads me to believe that the heat/AC might be on its own link like I thought (think) the radio might be. Next the dash comes out so I can start to investigate in there. Would that mean there is a 4th terminating resistor, somewhere on the heat/AC circuits?

Also, some terminology problems. OnCommand (Internationals service manual on CD) has extensive wiring diagrams. Lots of reference to "No Idle Engine Heat" circuit which appears to be different than the bunk heater and APU circuits. Anyone know specifically what they mean by this, as it seems to be closely tied to all the bunk lights, and maybe the remote sleeper radio? Also "Driver Display", I was assuming that meant the small LCD type display below the tach and speedometer but there is also various references to "Vehicle Information Display" and also "Driver Interface Display". These last two are tied to the "J1939 Adapter" which seems like a clearing house (at least on paper) for the J1939 bus. Need to find that in check it out, I guess. Anyone know what the different terms might actually refer to? 2014 Prostar.

Anyway, have to go to Oregon, then Kansas for family matters, so it will be a while until I am back poking in the truck. Taking the wiring diagrams with me. Maybe, just maybe will see something that helps.

Any thoughts or further questions to lead me somewhere would be welcomed. Otherwise, carry on, and don't go where I did if you can help it.