My truck gave me the dead battery symptoms and so i went and bought a new one. Whenever i try connecting the new one, the truck goes mad and by that i mean all electronics (lights, a/c, even water from the wipers) turn on even when in the off position.

Ohhh, by the way, the truck won't start.

Needless to say i disconnected the new battery until i can come to a solution. I'm afraid it might be the ECU needing reprogramming. Any help would be much appreciated.

 

'your truck'
really narrows it down. Its a mitsh, right?

I would expect all of that to be actually impossible, but if its new and computery, then meh.

Take all the fuses out. Fit battery.
Put them in one by one.

 

Sorry I made a mistake on my previous post. When i connect the terminals to the battery I can hear something turning on (humming) coming from the circled area on the attached pic.

When I turn the key to start the truck is when all electronics do turn on.

I have a Mitsubishi Endeavor 2004.

 

computery.

I imagine the noise is the fuel pump but unclear from that image.
Leave the battery connected 10 mins.
Then turn key to acc. for a minute, then to on for a minute, then try cranking.
-isolate where/when the problem is actually happening.