Just changed altenator and it will run then it
will shut off then battery is dead could it be
the battery or ecu/ fuse box relay I'm not
Note the diagram. I don't know what testing you have done? Make sure battery has a full charge and connections for battery and generator are all good. If battery is down use a charger on it, If the battery is down, we're just spinning our wheels as far as testing. The generator bat terminal, hot all the time, even with key out, use a test light to check. See the two fuses, the upper fuse is hot all the time. The lower fuse should be hot with engine running, voltage comes from asd relay for that fuse. There is a trouble code for your charging system, so check codes. Your charging system is pcm controlled.