Well, this could be something. Realized today that I never got around to checking out the suspension relay. Pulled it, and, although I'm not sure, it's conceivable it's the original relay and wasn't changed by the dealer when they did my compressor. Very plausible, as my CPO warranty probably wouldn't pay for something that wasn't just flat-out bad at the time. In fact, now that I think of it more, it's almost assuredly the original relay, unless my dealer just wanted to do me a solid.
I'm not really sure how to test a relay, so I went to an auto parts store to see if they could do it, with the relay in my pocket and not installed in the car. As I drove, the vehicle behaved the same as it has the last few weeks. I scanned the codes, and got the same codes I've been getting. O'Reilly's had a relay tester, but I couldn't figure out how to work it, and the kids there didn't have a clue, either.
At this point, I figure I might as well just buy a new relay for $22 and see if that fixes the problem.