So buddy from work picked up a nice 03 evo a few weeks back. But we noticed the tune was all kind of whack on it so i flashed the proper stock ROM onto it, and started from scratch. fast forward to tonight i flash an updated tune to his car and hear a fast click from what sounds like the engine could of been from the passengers side ECU area..

It happened after the flash finished so i unhook my laptop and go to fire his car and boom all lights go dead dash everything no power at all.
So now I'm thinking crap i killed his ECU i had zero power to anything while sitting there the power just kicked back in but as soon as i tried to fire the car all power lost again...

So we decide to get a new battery even though his load tested good. Put the new battery in and what do you know it fires up.
We drive it 5 miles or so park get out for a stop real fast come back put the key in turn it and again no power not just cranking i mean no lights no nothing.
I pull the battery terminal put it back on we have power again but it just clicks and loses all power again when you turn the key.
So we go around tighten every ground power wire there is on the car and in that time we get our power back and now the car fires up but for how long who knows anyone ever seen anything like this. Is there maybe a shorting relay and if there is which relay would it even be and yes i checked all fuses they are all good

It has now been driven a few miles and seems to keep firing up with no issues but it still has me stumped.
PS when we lose all power hooking jumper cables up does nothing it's like the car is losing connection somewhere.

Pretty sure at this point it has nothing to do with the ECU flash and it is just a random coincidence it happened at that point

 

Battery connectors/wires broken/corrode, battery ground wire problems?

I had same kind of problem of sudden powerlost and my positive battery terminal had come loose.

 

Everything was fairly snug when we went through everything we just synched everything extra tight. I'm really not sure if we fixed it yet it's just after we did that we noticed power was back and it fired up fine.
All ground wires are good checked alternator wire it's good and tight with no issue checked all fuses and trying to find out what each relay does so I can check into them.

Thing is it worked fine after the new battery also but then started up again.
But it's still leading me it's something in the + wire.
Becaus when I would pull it and put it back on I had power car just lose it as soon as I try to fire it up

 

Might just be time to take the car to English Racing and have them fix it.

 

probably just a grounding/corrosion issue like mobster said, these cars also have problems with the ignition switch going bad so that could also be an issue. The clicking after flashing is normal, my 03 does it all the time.

 

Have you checked the alternator? Just an idea, but car will start and run off the battery alone, so maybe it's just losing all power as the battery dies because the alternator isn't charging the battery possibly?

 

No I can't see it being the alternator because we did nothing but tighten everything up and it fired up also it's not an ignition switch it won't fire because the car has 0 power when it happens.
But at this point it hasn't done it again so

 

you probably fixed it by tightening down the grounds. The original problem description you gave screamed bad grounding to me.

 

Yeah, get back to us if it happens again. Otherwise, consider it fixed.

 

yeah its gone thru multiple fire ups now and driven the ground where pretty tight the one i noticed that i was able to tighten up a lot was the one with the fusible link<<? not sure if that's the correct name but for the alternator

 

which ground points? Same problem here