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Old 03-29-2020, 11:28 AM   #1
Country Coach Owners Club
Join Date: Jan 2020
Posts: 31
Cummins ECM Wiring Question

While under stay at home orders I've been on a seek and fix mission on my 16 year old coach. I came across the wiring to the J1939 diagnostic port for the engine and discovered two of the circuits have severely overheated and barbequed the wires/insulation on both ends (J1939 port and ECM on the engine). It appears at some point they were overloaded? Wires IB37 and IB46 are the two damaged which on the wiring list in the coach owners manual are listed as the "J1939 data link, rear reader port, ABS, Allison J1939 and resistor pack". In the chassis owners manual wiring diagram (pic attached) only IB37 is shown and listed as going to the port. Both wires have a larger 12ga wire in the harness which splits out into 2 wires each going into the plug. I assume this was an effort to increase ampacity through the small wires of the plug.

I checked for any voltage with and without the ignition on and did not see any power on these two wires. Not sure what happened to these wires or what to do about it? They both connect to the engine ECM. I presume if I ever needed to have a Cummins tech connect to the ECM I would be screwed. This is a little disconcerting with a computer controlled engine.

Today everything works but as we all know that does not last forever especially with computerized equipment.

The wiring harness from the port to the ECM is relatively short 2' and somewhat accessible. Not sure how all the other wiring that connects to the ECM interconnects if I were #1 find a harness and #2 replace it.

Any suggestions?
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CC 2004 33' Allure Seaside #31077 Cummins 400 ISL
Equinox Toad
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Old 03-30-2020, 06:38 AM   #2
Senior Member
Country Coach Owners Club
Join Date: Aug 2014
Posts: 130
At this time with the virus, I would look at Premiere RV in Junction city OR. They were in early last week, I would also try Country Coach Winnebago in Junction city as well. They are closed until April 13 their reply message was. "If you are in an emergency situation, we will have a limited staff working remotely to help with your parts or scheduling needs.
Please email: westcoastservice@wgo.net" I might send your post there.
Your local Cummins shop may also be able to help.

Jim E
2007 Country Coach Affinity
2015 Jeep Grand Cherokee
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Old 03-30-2020, 12:20 PM   #3
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Country Coach Owners Club
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Location: Alberta
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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)
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Old 03-31-2020, 12:40 PM   #4
Country Coach Owners Club
Join Date: Jan 2020
Posts: 31
I also found wiring cooked is the power up for the reader. Not sure why that would have got overloaded and fry the wires? I have seen reader ports under the dash and in the side compartment below the shifter. I assume one is for the Allison and under the dash is a second engine one?

I think my next step is to pay a visit to Cummins and see what they have to say. Not looking forward to the dreaded "oh its in a motorhome" response though.

Changing pins in the plug would be an option but a tedious process. I'll keep my fingers crossed everything stays working.

Thanks for the reply's
CC 2004 33' Allure Seaside #31077 Cummins 400 ISL
Equinox Toad
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Old 03-31-2020, 03:38 PM   #5
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Not common. Our coach is an older one but the data port J1939 worked fine when I read the data 3 months ago.

Other than Cummins, truck or auto electronic tech may be able to help you, too.
Steven & Polly
2000 Country Coach Intrigue 40'
2014 Ford C-Max Energi
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Old 04-15-2020, 04:30 PM   #6
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Replacement plugs are available on Amazon. Just search on the type of port you are looking for: J1708 or J1939. The pins configuration is different. You can get find a ‘pigtail’ version just install and rewire one wire at a time.
2006 Country Coach Inspire 360 Quad Slide
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Old 04-15-2020, 09:52 PM   #7
Country Coach Owners Club
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I did find some plugs and tools to get them out of the sockets on amazon. I haven't found a pigtail version yet.
I also found this site that offers cables. Per Mike I can unplug the connector at the ECM and plug one of his harnesses then connect a ODBII reader to see what is going on with the engine.

CC 2004 33' Allure Seaside #31077 Cummins 400 ISL
Equinox Toad
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cummins, ecm, wiring

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