Your mechanic must know my doctor he uses that 'old' excuse at times.
I did some reading and someplace someone said something about 'Combination meter' and 'Instrument clusters'. I am sure you must know more about this than I do. I went to the local auto electronics shop and he didn't have a clue about Prius electronics. Says something about the small town I live in.
Anyway, what I surmised is that the displays have a module that runs them, either both or singular, and apparently it also has something to do with my a/c. A Controller if you will. My dealer said I needed to replace the unit for ~$2500 ea. From what I understand the controller is about $200-300. It is electronic problem.
The problem is that this part along with the displays, are behind the dash which has to be disassembled to get at the unit. I hoped you could get at it thru the engine side, but this what I saw on a YouTube video.. only it was a diff year and very diff from my 05.
I have abt 123k miles, the engine works fine and a new car is not in the plan for another year. Hmm.. you know what they say about the best laid plans.... I really need the a/c I live in central Florida.
My car does that not shutting off thing too... you have to hit the start button the same time as the park button a few times or longer than my patience at times... then I shuts off.
My car, a 2005, needs the key inserted to start to my knowledge. Yours must be a newer model if you don't need to.
Mapquest will give you your speed if you are concerned. My one display, with the a/c control, etc. was so weak I could hardly read it, now it has brightened up a little at times.. it is possessed, maybe an exorcism will work
Hope you have better luck!