Ah, that does make sense based on the limited connections through the clock spring. So the steering wheel control module seems to be converting inbound signal properly, just sending outbound signals down the wrong wires on the head unit side? Any re-pinning possibility on that end of the adapter or is that impedance based, too? I'm just grasping at straws here, never done a head unit swap myself...
EDIT: Just hopped over to your full writeup, I'd guess it'd be very hard if not impossible to repin a 3.5mm jack LOL... Back to calling tech support I guess. Or just dealing with it as you seem content to do. Great writeup by the way!
Judging from the result, I would think the wires are crossed. The EWD states VOL is on SW1 and Hook is on SW2. Mine is giving me VOL from the HOOK buttons. When I swapped them prior I did not notice they went to normal, but I may not have reset the unit properly. Of course I will have to remove the HU now to get to the connectors. Sigh.
So yes, I am getting all the right signals (except MODE which I need to figure out), just on the wrong buttons. But the Universal aspect of this may not be internally mapping it right. I can't re-pin that as it is programming (assignment based). The unit has a re-assign function that was not working properly, so that is going to be the main thrust of the call. The 3.5mm jack is what the unit sends the final resultant command back to the HU through. On this JVC there is also a single wire which does the same thing (ground is handled separately). Apparently JVC (Kenwood) makes a device to supposedly wire into the main junction just like the AXXESS kit does, but with just the 3.5mm jack and three wires (ground, SW1 and SW2). I would be interested if that really worked. IN my case I just used the single wire and an adapter on the 3.5mm jack that broke the signal back out to two wires.
Using the handy TIS info (measuring the wire across ground with the button press):
VOL + is "approx" 1k Ohm resistance.
VOL - is "approx" 3.1k Ohm
SEEK + is 0 - 2.5 Ohms
SEEK - is "approx" 0.3 Ohms
No switch is "Approx" 100k Ohms
MODE is 0 - 2.5 Ohms (intersting as this is the same as VOL -, but on the different wire)
ON HOOK is "approx" 0.3k Ohms
OFF HOOK is "Approx" 1k Ohms
VOL and SEEK are on SW1, MODE and HOOK are on SW2. Adding in the splice hardware and disconnect hardware added resistance to the circuit, and to make the ground circuit work you add a ground wire which adds some length of 16 AWG wire, but I am not sure it added enough to fubar the values. What I can do is test the resistance of each button press with my setup and see if they are in the right ranges. But again I will need to remove the HU to get to the points. A weekend project.