Agreed it is probably the cable, though it could be the jack or a piece of crap in the jack. If you are using a cable with a 1/8" stereo plug on each end there will be 3 metal sections separated by 2 insulating sections. If you plug the cable into the aux jack and touch the 2 bands closest to the tip on the other end, the 60 Hz hum from power lines should be heard on the speaker associated with the band(s) you are touching. Make sure the volume is turned down to avoid damage to the speakers if you have an external amp. the stock HU does not have enough power to blow it's own nose.
2012 V6 4WD Ltd.
if you're not part of the solution, you're part of the precipitate.