2015 Prostar J1939 Communication Issues

Ok, I would start by pulling fuses one by one for any electronic module while watching your C to D resistance. Depending on the options ordered, on the 1939 you'll have the engine, trans, abs, body controller, cluster, compass module, tire pressure monitor, driver info display and front radar. So go through the back of the fuse panel cover and pull fuses for any of these and see what your resistance is and go from there. A common bad spot for the 1939 is right at the "Y" butt connectors between the main trunk and branch to the abs module which is located on the right side of the cab below the fuse panel mounted on the wall just above the floor. The butt connectors are very poorly done from the factory.

 

Ok, sorry, I re-read your post. The resistor by the DEF is for the engine private datalink for only the SCR stuff. Separate data link all together. The other terminating isn't always in the same place, but should be along the left frame rail under the cab somewhere sticking out of a main harness.

 

They can be hard to find.

 

Did you ever figure out the J1939 communication issues i might have the same problem

I owned 2015 international Prostar Cummins and with an automatic transmission. I have been fighting issue with electric fault on the dash every time the battery drains or if you let it sit for a week the Tcm would have to be programmed for the last 2 years money pit. Finally mid December when the tech hooks up the computer he was an able to see the Tcm . You can see the ecm and bcm but not tsm. He checked fuses all good. He thinks its the chassis harness, one of his other tech went through it didn't find anything. He suggested we need a new harness. 6 weeks to make it and $5400 for being not sure if its the problem.. any help or ideas. Thanks
PS.. 2021 we replaced the TCM with a new one.
2020 we replaced the harness that sits on the top of the transmission

 

Replacing the harness would be a fairly labour intensive project.
What fault codes are you getting?
Has anyone tested the data link at the diagnostic port with a multi meter? With the key
off measure between pins C and D with an ohm meter. The reading should be very close
to 60 ohms. With the key off measure between pins C and A then D and A both readings
should be infinite. Next with the key on measure between pins C and A and pins D and A
the reading should be close to 2.2 volts with C and A just slightly higher than D and A.
There are several power supply wires in the battery box that have fuses and connectors.
Check for corrosion on them. Look inside the connectors for melting plastic housings.
If you have any of the sealed connectors in the battery box with melted plastic housings
splice the wires to get rid of the connectors including where the power supply harness
connects to the chassis harness.
One should be tagged for the transmission, disconnect it in the battery box and and cut
the tie straps and pull it out and follow it to where it connects to the chassis harness.
You are looking for worn or corroded spots. Load testing the power and ground pins at the
TCU with a headlight might not hurt either.

 

I replied to your other thread, but I'll copy and paste here what I posted there so everyone can see;
I would say you have bad main battery positive, ground, ignition or datalink feed to the TCU connector. Next time the TCU is not communicating, remove the OEM connector at the TCU and check the following;
Pin 35 - ignition input (key must be on) 12volts
Pin 38 - main battery positive 12 volts
Pin 36 - main ground
Pin 2 - 1939 datalink - 2.4 volts (approx at key on)
Pin 3 - 1939 datalink + 2.6 volts (approx at key on)
At key off, you should have about 60 ohms of resistance between pin 2 and pin 3 to also confirm if your datalink is good. Main power and ground should also be load tested with a headlight bulb to ensure the wire can support good amperage. If all this is good, your TCM is faulty. Low voltage cranking will take them out.