I've been fighting this issue since I bought my 2008 Sig (yes, Kongsberg) in 2022. Symptoms: (intermittent, and not consistent) while driving, cruise control stops working, Medallion panel display reports engine communications failure, VORAD cruise reports fault, stops working (also stops cruise), accelerator pedal non-responsive, hard shifts. Except that the cruise would not work, the other problems resolved within a few seconds. At beginning, cruise would come back after stopping coach, turning ignition off and restarting. Later, this action did not resolve cruise problems, or fault re-occured within seconds/minutes.
I pursued various J1939 monitoring options, and checked all the J1939 bus connections I could find/reach. Finally, today, I found the 3 pin Deutsch connector to the engine severely corroded. I strongly suspect this has been this way since leaving the factory, based on how difficult it was to get to the connector through the floor hatches and cutting many tie wraps. The connector was difficult to pull apart, and the silicone seal fell into my hand when the connector did release.
If you're having similar intermittent issues, consider pulling the hatches and find this connector. I'd been blaming the Kongsberg, but it turned out to be something very basic, and once identified, fairly easy to fix. Well, assuming you have the right 3 pin Deutsch connector, crimp tool and shrink wrap.
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