I can't remember off the top of my head, but why not pull off the multiplug from the rear of the power socket and check at the pin terminals with a multimeter and the ignition turned on.
Another method is if you can't disconnect a circuit to test it, push a small pin or sewing needle into the wire through the outer insulation then measure between it and the battery neutral terminal, you will either see 12V on your multimeter when set to DC volts, or nothing if its the earth wire. You can then set the multimeter to ohms and check for continuity, if you then get a circuit its the neutral wire.
Probing the wiring with a pin is better than cutting the wires and having to rejoin (an old controls engineers trick). Be sure to reseal any tiny holes in the insulation afterwards with a dab of glue or paint to prevent moisture ingress and corrosion to the copper cabling. Obviously this method is not recommended on anything other than low voltage/low current circuits so don't go trying it on your households mains wiring.
EDIT: I had a problem on my early 2004 R1200GS with the power socket connector wiring corroding which needed replacing under warranty. Best slap some silicon grease or vaseline into the back of the multiplug where the wires exit to prevent moisture ingress and corrosion whilst you have it in bits.
