skyline

Hi I purchased an ECLIPSE ESIV Model 5441i few days ago and it works fine but this one does not have Aux Code input. I watched how people do add the Aux to old Car Audio on Youtube. but I want to connect it to the few wires in the round connector(this one has 12 pins) is there any way to figure out the individual pins? I looked up the manuals on google , unluckily, I could not find one cause the unit is too old. thanks in advance.