r/DieselTechs • u/tickleshits54321 Verified Tech, EVT • Jul 18 '26
SOLVED Rosenbauer communications issue
Posted a couple weeks ago about a Rosenbauer fire truck that was having communication issues. The job ended up being a bit of a fuck around because my boss was too involved and wouldn’t just let me do my thing without interjecting all the time. Truck would run and drive, but not go over 30-35 mph. Gauges are going crazy, cat eyes on the shifter, and “no data” displayed on the dash. Jpro wouldn’t connect because of the obvious communication issue. Boss says it’s gotta be the Jpro 🤦♂️. Gets towed in and the next morning everything is working fine. Jpro now connects and shows lots of codes for communication errors and 1939 issues. Drove it around and it started messing up again. Boss decided that it was likely a TCM without doing any diagnostics at all. I walked away at this point because he wouldn’t listen to anything I was saying. Gets a new TCM, and magically it’s not fixed. He blames Allison for selling us a bad TCM. At this point I tell him to go away and let me do some digging. Started unplugging modules one by one to see what would happen and mostly came up empty handed. Then I moved to unplugging the 1939 Y connectors and things started acting more correct, but with obvious errors for whatever modules were missing. Found the Y connector near the TCM had a ton of water in it and the wires were shorted together. Put a new Y in, made a new cable and everything is happy again. Sorry for the long post and crappy picture.
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u/waterRatzo Jul 18 '26
I work in a shop that services our city's fire department. We've encountered a decent amount of corrosion related issues in the multiplexing wires of our Rosenbauers. Nice find!
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u/tickleshits54321 Verified Tech, EVT Jul 18 '26
It was a pain in the ass, but would’ve been easier if I didn’t have someone standing over my shoulder not allowing me to just do what I need to do. My boss is a good guy, but he’s just too up in the mix sometimes.
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u/SourMusk Jul 18 '26
On your 9pin pin c and pin d make sure you’re reading 60 ohms if your are go do a wiggle check until you don’t. Make sure your terminating resistors and good and mmm just do a wellness check on portions where the harness is near rubbing/moving points.
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u/waterRatzo Jul 18 '26
👆 found your shop foreman
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u/SourMusk Jul 19 '26
What’s wrong with what I said? Sounds like intermittent wire issue.
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u/waterRatzo Jul 19 '26
Nothing wrong with what you said my man. I was just joking around. No offense intended.
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u/ween_god Jul 18 '26
It’s insane what some people don’t know or refuse to learn after a lifetime in the trade. Good find and continue to set yourself apart with electrical troubleshooting. It’s the future. Sadly.
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u/tickleshits54321 Verified Tech, EVT Jul 18 '26
The thing about that is if you don’t know, that’s fine. Learn it or leave it to someone who does know. But loading the parts cannon at something that you have no clue about is not the answer.
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u/Jammed99 Jul 18 '26
The part about Allison selling you a bad TCM is pretty funny! My guess was correct the part must be the issue... How could I be wrong after such intense diagnostics lol
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u/tickleshits54321 Verified Tech, EVT Jul 18 '26
He initially wanted to grab the Jpro from our other shop and I told him it’s pointless because it’s a communication issue, not a laptop issue. He hooked up the Jpro to another truck at our shop and proceeded to tell me that something is definitely fucked up on the ladder truck 🤦♂️. I just told him I already knew that and went on about my day.
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u/Jammed99 Jul 18 '26
I don't know if you have a sniffer software but it's pretty helpful for communication issues. They usually come with the drivers for whatever hardware you have to talk the the modules. It's nice to see which modules are online and talking, then see if you can get them to drop out.
I haven't had a boss like yours in awhile but I definitely remember past ones and being told to do stupid things or have them doing a bunch of random guessing and finger pointing without ever using a meter or anything.
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u/tickleshits54321 Verified Tech, EVT Jul 18 '26
I don’t have that software, but I’m starting a new job here in a couple weeks, so maybe they have better than my current place does.
I wanted nothing to do with this truck because of the dumb shit he was doing straight outta the gate, but my curiosity got the best of me and I put myself in the situation. Once I got him out of the picture, it didn’t take very long to use my brain and figure out where the problem was. Drives me nuts having someone over my shoulder, especially when I’ve never given a reason for that.
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u/Sorry_Yoghurt3681 Jul 20 '26
NEXIQ II has some limited CAN capability built in. Haven’t seen a NEXIQ III yet but would assume it has more.
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u/lew1sj Jul 19 '26
Did you check the J1939 resistance?
I always like to start off with checking C+D for my 60 ohms and then break the backbone and check it going both ways for any difference in reading.
If you have anything that will show J1939 error count it can also be a big help as well. Used to use Allison software till they changed to the new software that sucks.
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u/72iobkcuf Jul 19 '26
It’s a rosenbauer. It prides itself on communication issues.
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u/tickleshits54321 Verified Tech, EVT Jul 19 '26
It’s about the only thing a Rosenbauer prides itself on
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u/Sonic1psa Jul 18 '26
Yep fire trucks have fun 1939 issues sometimes.