Computer problem ECM or TCM

I was driving up highway, truck was fine, then lost power, slowly shut off. Truck I thought ran out of gas, it did not. I have read these trucks have problems with IPDM and ECM. with from what I read the ECM is a relay in the IPDM board that can be replaced with the fog light relay. I tried that, no luck. I have changed the crankshaft position sensor. no luck. I changed the oil pressure sensor. No luck. I bought a scanner, when plugged in I get a error can not communicate signal. So now I cannot even read what the OBDii codes may be. I have a feeling it is a in the main computer or the TCM. I have had been having problems with TCM board since winter. I just had not changed it yet. I cannot use, cruise control, transmission manual shift, four wheel drive so forth. I would think it was that, however, I did not think that could stall a vehicle out and then prevent from starting again. truck is older, I am handy I do not want to pay big shop cost on a truck so old with such high mileage, plus now I am determined to figure out. Any help would be greatly appreciated.