I do not have a wiring diagram for this car but hopefully someone will come along soon that will.
A good way to check it though is to pull out the dash and rub and push the wires and watch to see when it loses power.
You most likely have a short to ground or to the 12v feed. If you wired the radio your self you can see what wire they have in common. They either use the same power or the radio gets power from the dash. Or they use the same ground.
Is anything aftermarket?? alarm, stereo, remote start?