Suburban shutdown

99 suburban starts, then shuts off immediately. No sputter, or idle down just shuts off like I turned off the key. Wait between 10 min and a day then it will start fine. There is no resister in the key. No mechanic I have talked to has a clue. Replaced Key, ignition control module, gas cap, and long block(that was a different issue). HELP, I need this to work.