I'm sure about the connections, for certain values of "sure."

I used a multimeter to quadruple-check that the pin numbers are identical for my OBD-II-to-DB9 cable I'm using for the main CAN bus (the one that works) as they are for my custom radio harness to DB9 cable that I'm using for the CAN-B bus (the on that doesn't.)

The "good" news is that I'm getting at least some radio-related output on the "main" CAN bus. I haven't decoded it yet, but I definitely get unique message when changing inputs, presets, etc. I was led to believe all the radio-related stuff was on CAN-B, but that doesn't seem to be the case.

Figuring out how I can *initiate* these might be tougher, though I did get some code from someone who did it with an older Chrysler radio that I'll probably try tonight.

For now I'm going to work with the bus I can read, and if I can't make any progress, I guess I'll have to buy a scope or logic analyzer.