J1939 Diagnostic Port

[shepardmike]

Does anyone have the pin out for the diagnostic port on a 2018 Freightliner w/Cummins diesel engine pusher?

[jharrell]

Is that all you need because that is a pretty easy google search? All the magic happens on C & D which is where the complexity occurs.

If you want to read the data something like Bluefire is a good start unless you know what you are doing rs-485/CAN digital protocols

[shepardmike]

Perfect! Thank You...

[shepardmike]

My BlueFire works from the engine compartment port, but doesn't under the dash. No lights on the BlueFire, and I tried a different scanner, which didn't work either.

With the diagram provided by jharrell, I was able to check to see if I am getting any voltage and I am not. I did notice a 5A fuse labeled Diag in the fuse panel but it was good.

Any thoughts on why the front diagnostic port is not getting power?

[Skip426]

Contact Freightliner with your serial number and ask for a wiring schematic for your chassis ; tracing the circuit from the connector to the power source will tell you if the front connector is fused differently than the rear.

Freightliner Free Help Line

1-800-385-4357

[shepardmike]

Call FL, spoke to Matt. He pulled up WD and didn't see any fuses. Told me to take it in, which is expensive and time consuming.

I have a J1939 plug with a pigtail of exposed wires. I guess I will trace it with a Fox and Hound.

[DancinCampers]

FWIW, Shortly after we purchased our coach new in 2012, the owner of 3ts in Lake Havasu, a member of the Las Vegas WIT club, plugged in to the front port under dash and it did not work. After he contacted someone, he had to disconnect something on my DEF system on top of the tank. It then worked. I didn't ask him exactly what he did. When he was finished he reconnected. Ever since then techs have only used the rear plug