Not positive about '05, but I'm guessing your Mech was guessing. On most prior years, the 13 pin (round plug, square pin pattern) was to hook up the optional 6 disk in-dash CD changer. But that doesn't change the answer much. I've been searching a couple weeks and haven't found a pre-made adapter to convert the CD-Changer input to an AUX input. Pin designations are available at http://carstereohelp.net/wireharness_Mitsubishi3.htm If anyone knows of an adapter for these units, please post!