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Old 02-20-2021, 08:00 PM   #1
Skoolie
 
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Looking for a J1939 wizard

Hello,
I was able to fix almost all of the many issues following the engine and transmission swap, but the last one got me.
The J1939 bus is acting weird.
1. Very slow transmission of the data. There is a 5-6 seconds delay for the Bluefire to update the values (rpm, etc. ...). Not a Bluefire issue, before the swap it was working just fine.
2. The TCM is throwing a "U0115" code, meaning it lost the communication with the ECU.
3. DTC from the ECM for coolant level critically low and IAT out of range, high. I don't know if these codes are related to the J1939 issue.
I did test the resistance between the high and low legs of the J1939 wires, and got 58 ohm at the 9 pin connectors and 59 ohm at the TCM plug. Looks good, right?
Any idea how I should investigate (and hopefully, fix) this issue?
Thanks!
S
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Old 02-20-2021, 09:06 PM   #2
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Hopefully, CadillacKid or Booyah will reply. They seem to always know the really in depth answers.

Hang in there...you'll get it figured out!
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Old 03-04-2021, 08:43 PM   #3
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Originally Posted by Simplicity View Post
Hopefully, CadillacKid or Booyah will reply. They seem to always know the really in depth answers.

Hang in there...you'll get it figured out!
I sent a PM to Cadillackid a few days ago, no answer. I guess he doesn't have a clue on what is the issue ...
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Old 03-04-2021, 09:30 PM   #4
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Originally Posted by ABBus View Post
I sent a PM to Cadillackid a few days ago, no answer. I guess he doesn't have a clue on what is the issue ...
He's been missing for a few days, I really doubt he doesn't have a clue. Someone will be by shortly
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Old 03-04-2021, 11:45 PM   #5
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2. and 3. are solved.
But there is still a "lag" in the J1939 feed, as the Bluefire shows values (boost, rpm, speed, load, ...) with a delay of 5-10 seconds.
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Old 03-05-2021, 05:12 AM   #6
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Quote:
Originally Posted by ABBus View Post
2. and 3. are solved.
But there is still a "lag" in the J1939 feed, as the Bluefire shows values (boost, rpm, speed, load, ...) with a delay of 5-10 seconds.
For the record, what did the problem(s) end up being for 2 and 3?
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Old 03-05-2021, 11:32 AM   #7
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Quote:
Originally Posted by ABBus View Post
Hello,
I was able to fix almost all of the many issues following the engine and transmission swap, but the last one got me.
The J1939 bus is acting weird.
1. Very slow transmission of the data. There is a 5-6 seconds delay for the Bluefire to update the values (rpm, etc. ...). Not a Bluefire issue, before the swap it was working just fine.
2. The TCM is throwing a "U0115" code, meaning it lost the communication with the ECU.
3. DTC from the ECM for coolant level critically low and IAT out of range, high. I don't know if these codes are related to the J1939 issue.
I did test the resistance between the high and low legs of the J1939 wires, and got 58 ohm at the 9 pin connectors and 59 ohm at the TCM plug. Looks good, right?
Any idea how I should investigate (and hopefully, fix) this issue?
Thanks!
S
1. I have no experience with bluefire. With nexiq usblink they have a device tester function that wil show the raw data being transferred real time on the bus. Does bluefire have something similar?

What I typically see when the diagnostic program has a delayed value update, it's because the computer's hardware doesn't have the ram or processor capability of monitoring/updating all of the pids I'm trying to view. Closing some of the pids you're monitoring will help reduce the workload, or update your hardware system.

2. Typically is caused by faulty ecm's, loose connections, and even poor battery connections. It's best to see if it's an active or inactive fault and go from there. I've seen nearly dead batteries cause this at startup. They're good enough to crank, but the voltage drops low enough that communication stops.

3. Probably not. See if they're active and troubleshoot them seperately.

4. It depends on the accuracy of the multimeter. I think theoretically your allowed a 10 ohm variance, but I've seen data buses that ohm'd within spec, yet had communication issues. Did you check for continuity between the bus terminals and power and ground?

I doubt your lag issue is with the data bus, and more likely with your tablet/bluefire device. What year/model vehicle are you working on?
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Old 03-05-2021, 11:49 AM   #8
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Thanks for your reply!
The Bluefire was working fine before the engine / transmission swap, that's why I don't think the issue is on this side.
I did test the continuity, no issue here.
IC RE 2013, Maxxforce DT.
I can read the raw data with either ServiceMaxx or Allison Doc.
My last theory is there is something wrong with the ECM "calibration". The engine is not from a bus, so maybe some things in the parameters are wrong (speed source, it is set on "oss hardwired", maybe I should try "J1939 public"? Same this for the output shaft teeth count, set on 43, looks weird (I think it should be either 16 or 40).
Anyone able to get an engine file from a RE school bus with a Maxxforce engine?
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Old 03-18-2021, 04:57 PM   #9
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Fixed. I don't exactly know what was wrong, as I changed many parameters in the ECU.
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Old 03-18-2021, 06:22 PM   #10
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somehow i missed this thread.. glad you got it all going!!!
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