Working on a friends car, it's a 2000 Civic SI with an H22 swap and an OBD1 conversion. His car keeps dying and to start it back up, he has to remove the white wire going into his fuse box up by his battery. It's the wire furthest towards the front of the car in that box that you typically have to unscrew in order to remove the engine wiring harness. When the car is off, I'm getting ohms of it being grounded while it's off the fuse box. When the car is on, it's no longer getting ohms to the negitive side, but now it's getting 15.5 volts to it.

Obviously something is going on with this wire because the car runs while it's off which isn't supposed to be, grounds are good all throughout the engine. Any suggestions other than pull the wiring harness?

 

That is the charge wire from the alternator.
Thats why your getting 15v when the engine is on and continuity to ground(because the alt is grounded on the motor).

As to your problem, I am unsure.

When you pull the white wire and start it, are you getting a battery light?