Tried getting a stock read off an 05 lly and got a communication error. Truck had no communication from ecm what so ever but everything else was reading. Customer had a spare ecm so we plugged it in and truck would turn over. Tried to download a stock file on the second ecm and it went dead just like when I was trying to read original ecm and said communication error. Customer took into gm dealer to have it flashed back to stock and they said they can’t even see the ecm to flash it. Any help would be greatly appreciated.