Great to finally see someone who has some actual knowledge and understanding of this system! Tried to get wiring diagram from FR and Chevy but neither will release them because they are "proprietary intellectual work products".
This post is about my son's rig and I've been trying to assist him (ET) since this is his first RV and he has not been able to even use it. Every time he goes out (half dozen or so) the engine will not start and it has to towed back to the dealer (one tow was over $1,000).
There's an intermittent electrical issue which no one can identify. The dealer blames the FR wiring, FR blames the Chevy engine control system, and Chevy blames FR and the dealer for modifying their engine control system. Sadly, he making a hefty payment for an unusable RV which no one know how to fix, nor how to get him out of the unsolvable mess.
Thanks again! This the first usable information we've seen in all these months of researching the problem.