Hi, first post here and I know it was posted 6 months ago but just wanted to say how useful this thread has been! I'm going to be creating a wired remote control out of my 14 year old tape player (using the buttons on the front of it) to control a new pioneer DEH-2920MP mounted out of sight in the glovebox, to deter the thieving scum round here who stole my last lot .
I've just been and tested the resistor chain mentioned (on a DEH-2920MP) and it's all spot on, but I'll fill in one of the gaps:
This changes the display - in (FM) radio mode it changes between frequency, station name (from RDS) and station type (also from RDS), and in CD mode with an mp3 CD in it switches through various info including track title, artist name, file name, folder name and a few more. I couldn't see any effect for 33.6k either.6.6k Ω List(Disp) (No apparent effect)