First thing I would check is the battery connections. Make sure they are all clean and tight and corrosion free. IF the cables check out, it is highly probable that the ECM is the issue. Since it is mounted under the hood and exposed to the elements, it's more problematic than most others. If the service number on yours is 1227727, that model is especially problematic. The seal between the two halves is junk and allow water in. If you need a new ECM, don't bother with a used one. If you get a reman unit, stay away from the brand Cardone, as they are not very reliable. Stick with AC-Delco or Standard Ignition brands if you can.