Wait to start light wont illuminate.

Are you sure that the ecm was bad? It sounds like whoever diagnosed the bad ecm might not have gotten the diagnosis right. If there is no power to it right now, then there probably wasn't power to it when they diagnosed it as being bad.
Some of the things to look for are corroded battery cable connections. Corrosion in or under the engine fuse box. Wiring problems from the fuse box to the ecm.