A few days ago, I posted a notice about reinitializing the radio after the battery is disconnected. I don't know if Honda calls it "initializing," but you get the idea.

It's good I happened to see that instruction because I needed it today. I was making a connection to the battery on my son's Fit, and the battery must have lost contact for a second. The radio wouldn't work. Without stepping on the brake, I pressed the Start button once, and the head unit turned on. Then I held the power button for two seconds. That got it working.