Hi Marc , sorry for delay. Looked at the ecu on the drivers side under the trim, connections fine, I then found the other one exactly where you said on the bulkhead behind the top ecu cover. I managed to find a replacement from a scrap Sierra and swapped it out. Part number 87BB10K910AB 012933 84596B
As soon as I did, everything lit up like a Christmas tree!
thanks for the info, really appreciated.
off to the RS annual meet at Mallory park the w/e so nice to have (most) things working!
cheers! 🍺