I recently got this warning message on my PCM. . .
After pressing ENTER the PCM initially only displayed the time and temperature.
After a while it would show AM and FM stations but no sound and pressing SAT or CD gave me a “Not operating/installed message.”
Stopped the engine. Waited 1/2 hour, restarted engine and all seems to be working well again. I was in Palm Desert at the time, outside temp 110 degrees F. I drove home and the temp cooled to 81F. Maybe that was the problem.
My best guess is the AMP was acting up. I’ll have to keep an eye on it in the future.