I took apart the interior and had everything out through to the firewall. Now everything is back together but the iPod interface doesn't produce any sound, if I turn up the volume I get some very regular clicking, perhaps voltage pulses which is why I suspect its the wrong wire.

I need to confirm I have the correct 3-pin wire back here. The module seems to be working fine, iPod shows the MB logo and I have control through the steering wheel + cluster.

Hopefully someone has photos from working on it previously, or can take theirs out to have a peak. I looked in WIS and it has black/yellow/brown, but I didn't see a cable like that, and all others are accounted for. CD changer works, and it has the only seemingly-interchangeable cable.



Update: after further research, I'm fairly certain this is the connector for the parking distance lights at the top of the dash, so they must've been swapped.