A have a 2015 PIU as well, and I was able to add an AUX interface.
Note that I'm standing on the shoulders of giants here
shout out to De-Policify and ExplorerPIU specifically
After reviewing the work of others, I removed the center instrument panel and the CD Player. I disconnected the 24 pin cable and took pictures. Then I verified and labeled the pin locations to be sure I had a correct reference before I started any modification.
I harvested some pins and wires from a random harness I had in a junk bin. The pins were slightly too large, but it was the closest thing I had, and I was having no luck finding a better source, so I decided to try and make it work. I also found an old AUX cable, chopped the end off, soldered the three wires in place, and applied heat shrink to each wire, then another layer of heat shrick over the entire area. I tested each pin for continuity back to the tip/ring/sleeve.
Wire colors don't matter, but in my case:
Pin 17 gets a red wire to tip
Pin 18 gets an orange wire to ring
Pin 6 gets a blue wire to sleeve
Because my pins were slightly too large, I wound up needing to drill out the plastic slightly on the 24 pin connector. This allowed me to insert the pins at a slight angle before using a small pick to snap them into place from the front side. Again, I didn't love the use of the wrong size pins, but I was using what I had to work with.
The connector slid into position on the back of the CD player with ease. I watched carefully for any movement of my extra three pins but saw none. I started up ForScan, made a backup, then changed the value to enable the AUX interface. After saving and restarting the vehicle, I plugged my new AUX cable into the headphone jack of my laptop and played some music. I was able to press the AUX button and see the "Line in Active" message. I turned the PIU radio volume knob and heard sweet sweet music coming from my PIU's speakers. Success!!!
I should mention a bit about making the change in ForScan.
After selecting FCDIM, you will find 7A5-01-01. You will see 3 groups of 4 hexadecimal digits. In my case, I had a "5" in the first digit of the second group of 4 digits.
Here are all the possible values I am aware of:
5=AII not present & IT push button start & Fader enabled,
4=AII not present & IT key start & Fader enabled,
1=AII present & IT push button start & Fader enabled,
0=AII present & IT key start & Fader enabled,
9=AII present & IT push button start & Fader disabled,
8=AII present & IT key start & Fader disabled
I chose to use the value 1 as you can see in my screen shot above. That is the only digit I changed. Then I pressed "write all" and when I did there was a warning message about a bad checksum. I had previously read that you can ignore the checksum warning because this checksum will simply be recalculated and applied if you choose to proceed, so I did, and it worked as expected.
Conclusion
This mod isn't too difficult. In my opinion, its absolutely worth the effort. I think at this point there are several good examples of how to add an AUX interface to one of these PIUs, but perhaps my comments and pictures will be helpful to someone. Happy modding ya'll.
