If it shuts down the computer then sometimes you have to turn on turn off turn on turn off then on sometimes,if this happens watch your RPM gage mine go down below 1 sometimes shut off do steps above make sure key off before off/on start car watch RPM go to normal I know because it happened to me wire crossed,now no problem only if your computer shutS down,I'm good now lol

I still don't understand 4 wires on positive can I hook just the key ignition to shut down not the computer,I'll try separating the key switch from the computer wire on positive post keep power on computer,radio not key,I wonder