Has this happened before, or do I have a scary problem. On my 2004 Yukon Denali, my battery went stone cold dead (0 voltage), and I picked up a replacement battery. I connected the positive terminal, and then the negative terminal, and the vehicle started and ran by itself. There was NO key in the ignition, and I don't even have key fobs for it. Putting the key in the ignition did nothing. Disconnecting the negative terminal did nothing, I could not kill the engine till I pulled the fuel pump fuse. Needless to say I was more than a little concerned as if something or a body part had been in the belts, etc., it could have been catastrophic. I replaced the fuse, and repeated connecting the negative terminal, and it did it again, no key in the ignition, and no key control of the car. The third time the car did not start, and placing the key in the ignition did allow the engine to be turned on and off properly. Do I have some sort of problem with an ECU in the engine. I don't want to put my hands around the engine without pulling the relays for the ECM's, and I am not sure on all to pull. I am going to be scared to work on the vehicle without these procedures, killing the fuel pump would still allow the engine to run for a short period. Is this normal, or something that could happen because of the zero voltage on the system? Or do I have a weird electrical problem on it that should not be there. Needless to say, the other functions the ECU runs such as the air bags scare me if I worked around the dash because of this spontaneous problem. Anyone with any insights?