Logistically, I suspect it's located close to the drive engine. My ECM is fastened to the frame of the engine compartment under the bed, above the engine. Which means the location was determined by the coach mfgr, instead of chassis mfgr.
AI is giving me what looks like very specific and potentially good info. I skipped over the post earlier as I am not into that sort of thing and really had not info other than what is commonly available on many of the AI sytems.
For the full story which is quite long with far more details, I suggest going direct but this is the short answer it gave me? No warrenty on resluts, though!