CD player (whole radio) turned off. A/C turned off. Engine turned off. This noise happens when the key is simply in the ignition and turned to the on position, with everything else turned off that can be.
I checked for CD player noise and it's not that.
I guess I won't really know without trying to get a look inside the dashboard. Somehow. Maybe pulling fuses selectively to see when the noises stop might be a good diagnostic.
However, given that this car is so computer-dependent, I'm not sure that just randomly pulling fuses is advisable.
I went to the local salvage yard today to try to find a couple of parts. I did find one, a new A/C console vent panel. Well, new enough. It's perfect. My existing one had
some finish loss on the top edge.
I pulled the replacement from a CTS that had a very violent last moment. The roof was crushed in, and the only sheet metal on the whole car that was possibly reusable was the door skins
on both right doors. Hood, smashed, Trunk, smashed. Left side doors, smashed. Roof, smashed. Fenders, both smashed. Rocker panels, bent and smashed. Quarter panels, both bent and smashed.
Surprisingly, though every airbag was deployed, there was no blood visible in the car. Reportedly, the driver walked away with minor injuries.
It made me feel SAFE in my CTS.
I should probably spend some time inspecting that and other CTSes in the junkyard next time, so as to familiarize myself with how they're put together and figure out how to get to things without doing damage.