[Uwon]

Looks OEM by the look of the end fitting. Could be anything. I presume that you have checked that everything works in the car. Was the radio replaced and perhaps power was spliced in elsewhere? Any other mods? I would check with a meter and determine if its grounded. If not, then test for power with ignition off then on, then turn on electrical equipment one by one. If not found, cap it off and go for a ride!