I am attempting to retrofit a 2009 accent xm/mp3 headunit into my base model 2008. The 09 headunit supports and AUX in and USB. The AUX input has 4 wires but I do not know what the 2nd pair of wires are for. Here is a picture of the pinout:
the pins in question are 2-1, 2-2, 2-3, and 2-4
what are 2-3 and 2-4 for? AUX REF and AUX DET???
any help is appreciated.

the pins in question are 2-1, 2-2, 2-3, and 2-4
what are 2-3 and 2-4 for? AUX REF and AUX DET???
any help is appreciated.