I've been using a cheap cassette adapter to use my phone to play audio in my 2003, and while it does work its quite annoying. The mechanism is loud and tends to get quieter over time until I take the tape out and put it back in. To fix this, I pulled my cd player out and found it has a fixed cable with two electrically identical 12pin connectors on it. I found a cheap aux adapter here on amazon, and y cable meant for other toyota's that seem to use the same connector, and am thinking about ordering it, rather than doing further reverse engineering work to make my own. Do these work properly with the prius? Its not listed as a supported vehicle but I know its a rather low production car and figured it might have just been missed.
I went through that process with my Gen 1 and an adapter from DICE Electronics. The saga was in ➡this thread⬅. That adapter was a little different: it didn't just replace the CD player, it came with a Y harness so you still also had the CD player. It identified itself as a mini-disc changer, which is assigned a different AVC-LAN address than the CD player, so both would show up as choices on the touch screen. That unit would also let you plug in an old iPod and let you scroll through it on the touch screen. It would show track titles (subject to the number-of-letters limit for mini-discs). You would use the aux jack by selecting a special mini-disc number, 6, I think. They only advertised that unit for gen 2 Prius, and there were some minor tweaks needed to the Y wire harness to get it working right in gen 1. The harness needed four more wires added (where the supplied connectors just had empty holes and no pins) that, in gen 1, are needed for the clock and the dash buttons around the cluster to work. And the supplied harness had an unexplained splice in it that ended up, in gen 1, confusing one side of the AVC-LAN pair with the cassette eject button, of all things. Little snip there and it all worked.
