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Discussion Starter · #1 ·
So I finally got my green J1939 connector wired in to my 2001 170 isb 3.9L motor and it doesn’t connect with Insite for some reason. I wired it as

A- chassis ground
B-constant 12v +
C-1939 signal Ecu pin 53
D-1939 return Ecu pin 52
E-shield Ecu pin 51
F-1708 supply Ecu pin 31
G-1708 return Ecu pin 30

I have verified continuity and ground. My buddy had to use an adapter to connect to the green J1939 plug.. Any ideas? Below is the diagram I used for my wiring.
 

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Wiring looks right. Are you using shielded wire?
Make sure the harness is plugged into the computer all the way. I had an issue with that.

My best guess is something with the adapter. I would research/check to make sure the adapter is pinned right.
 

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Discussion Starter · #3 ·
Yes I am using shielded wiring. Good point on checking the connector I’ll look into that. My buddy that brought Insite over said he uses that same adapter to tap into some of his fleet school buses so idk
 

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1964 Chevy C10, Cummins ISB170, Allison 1000 5 speed, full float 9”, ECU Tune, 5/7” static drop
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You need a backbone harness built. You need 50-60 ohms of resistance on a J1939 circuit. It is similar to RS485 high speed data communication. If you take a voltmeter and ohm Your connector j1939 signal to j1939 return with the key to your vehicle off you should read 60 ish ohms, if not then it will not communicate. You need two 120 ohm terminating resistors in parallel to your signal and return 1939 wires. Typically they are deutsch DT 3 way connectors.

 

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Discussion Starter · #5 ·
You need a backbone harness built. You need 50-60 ohms of resistance on a J1939 circuit. It is similar to RS485 high speed data communication. If you take a voltmeter and ohm Your connector j1939 signal to j1939 return with the key to your vehicle off you should read 60 ish ohms, if not then it will not communicate. You need two 120 ohm terminating resistors in parallel to your signal and return 1939 wires. Typically they are deutsch DT 3 way connectors.

please excuse my ignorance to this but how would I wiring this connector in with the rest of the wiring? Thank you for your help
 

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Is there any reason why you couldn't just put a 60 Ohm resister across the signal and return lines at the connector itself? It would perform better with less reflections. Or is there no room inside the connector? I need to build one of these for my ISB170 too. Figuring this all out should help me too. Thanks for the help. Gene
 

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Is that about a 2.5W resistor (12/60=0.2A; so 0.2 * 0.2 * 60 = 2.4W)? Maybe that is why they use two 120's?
 

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Is that about a 2.5W resistor (12/60=0.2A; so 0.2 * 0.2 * 60 = 2.4W)? Maybe that is why they use two 120's?
Ummm, I think you are confusing digital signals with 12 Volts direct current. Stay tuned for someone who knows more about j1939 connectors...
 

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50% duty cycle on the digital gets you down to 1.2W or so. Again, lots of potential power there. If the line is only 5V, it'd be way better. Anyway, that's my question really. How much power does the 60 Ohm have to dissipate? Max possible is around 2.5W or so. Reality is???
 

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The CAN wires must be twisted pair for noise rejection and minimal noise radiation. As mentioned, each end of the bus needs to be terminated with 120 ohms.
 

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1964 Chevy C10, Cummins ISB170, Allison 1000 5 speed, full float 9”, ECU Tune, 5/7” static drop
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You want two 120 ohm resistors as far apart as possible. Typically you would have one at the beginning of the communication circuit and one at the end, it “balances” the circuit. In heavy duty trucks you will see them in the cab and they will be at opposite ends of the circuit. You can read up on RS485 communications if you want the theory, I just go for knowledge on the application.
 

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Here is some good reading, describing all any user of CAN needs to know about the physical layer.
 

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So I finally got my green J1939 connector wired in to my 2001 170 isb 3.9L motor and it doesn’t connect with Insite for some reason. I wired it as

A- chassis ground
B-constant 12v +
C-1939 signal Ecu pin 53
D-1939 return Ecu pin 52
E-shield Ecu pin 51
F-1708 supply Ecu pin 31
G-1708 return Ecu pin 30

I have verified continuity and ground. My buddy had to use an adapter to connect to the green J1939 plug.. Any ideas? Below is the diagram I used for my wiring.
I hope someone can jump in here with a quick reply. I'm wiring up my 9 pin BLACK diagnostic connector so I can get my engine fired up this week. I have all the wires accounted for except the ones in H (Orange/Black) and J (red).
I'm wondering if the red is the B+ from pin 8 in the ECU and the orange/Black is pin 79 which is the diagnostic sw.
I read someplace that the diagnaostic sw has to be on to read the ECU and think maybe the Cummins inline tool connects that when plugged in?
 

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1964 Chevy C10, Cummins ISB170, Allison 1000 5 speed, full float 9”, ECU Tune, 5/7” static drop
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I hope someone can jump in here with a quick reply. I'm wiring up my 9 pin BLACK diagnostic connector so I can get my engine fired up this week. I have all the wires accounted for except the ones in H (Orange/Black) and J (red).
I'm wondering if the red is the B+ from pin 8 in the ECU and the orange/Black is pin 79 which is the diagnostic sw.
I read someplace that the diagnaostic sw has to be on to read the ECU and think maybe the Cummins inline tool connects that when plugged in?
Pin H and Pin J are not used on your 9 pin connector.

the diagnostic switch will allow you to read ECM codes if you do not have a computer. If you turn on the diagnostic switch it will cause the amber light (maintenance lamp) to flash in sequences for codes.
If you access quickserve you can find more in the operation and maintenance manual on the diagnostic switch. Under “101-007 Electronic Controlled Fuel System”.
 

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Thanks for the fast response!
I wonder why my 9 pin has those wires in it then. I do not remember them being in the harness on my Dakota but really cant remember that far back. I'll leave them exposed and carry on without them for now. I can always add them in if required.
 
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