Ive ran into this a few times myself where wont power up or start all fuses good jump start relay and cranks. read and seen where most times its DESS post. My question is Ive got one in shop and in my mind even with bad post shouldn't pressing start button power up unit but give wrong lanyard beep? I'm sure I'm wrong and going to give a new post a try and order another. Ive encountered this issue myself and have another doing this right now. what bugs me is scantool says cant find ecu and Ive bolted on a used dess gunge and ecu I had and no go. What bugs me is when unplugging and reconnecting dess harness I don't get that short horn squeal but do on the used unit. your thoughts please