Thanks for the welcome and the response, Blazernut. I can't say for certain that I had the battery lead off for 20 minutes. I'll have another go at that.
There is another factor to weigh in, but as it's been an issue for several months, I didn't think it would be related. I had a bad wheel bearing, and had a shop replace it. When we got it back, the ABS light was on. The shop manager said his mechanic didn't get the sensor out of the old hub, and we'd have to come back in to get a new one.
I'll spare you the rest of the details going back-and-forth with that shop, but regardless...the ABS light was on for a few months, then my current issue started recently, with the red brake light in the display and the "service brake system" message. I assumed these were separate warnings, but perhaps they're related.