I just learned something I thought I might share. My friend the toyota technician was showing me that the console screen computer has a diagnostic mode. By entering this mode, you can see various information about the system. Unfortunately, it is stuff only related to the screen, the navigation system, and stuff like that. However, one neat feature is that it actually will show a live volt-meter of the 12V system. So if you are ever in a situation you need to see what the 12V battery is up to, this might be a handy tool. The procedure is: Car must be in park parking brake must be engaged Radio must be on, showing the screen where your 6 station presets are. hit the "display" button to bring up the brightness/contrast settings. At this point, you are ready to enter the diagnostic mode. There are two hidden buttons on the screen. Both of them border the left of the screen in an empty area that is unused by anything else on the screen. One is at the top, and one is at the bottom of the unused area. There are a total of 6 taps, in this order: top, bottom, top, bottom, top, bottom. If you did it right, you will see an immediate result. It will bring up an initial diagnostic screen but you will have to wait a moment for it to complete self-tests and give results. After that you can click "menu" and go from there.
Not unknown to the senoir citizens here, but thanks for bringing it to more general attention. If you compare the battery voltage screen reading to one made directly on the (trunk) terminals you will find the former about 0.2 volts lower. Voltage drop along the line to the front of the car. If you enter this mode when Prius is 'ready' you should see about 13.6. When Prius is 'not ready', it depends on the battery condition, less than 12.3 would not be so good. You can also pull it down with headlights or other electrical loads.
A cheap fix, clean and re-seat the ground cable, both ends, and the terminal post connectors. Corrosion is the little thief but the battery does seem a little weak. Bob Wilson
11.6 in ready mode indicates a bad 12 volt converter, or a really really bad 12 volt battery. When my converter overheated in the summer ( due to bad inverter pump ) i kept a real good eye on that screen because my 12 volt battery would keep discharging, and i would lose all my dashboard lights and stuff. Normally its supposed to be >13 volts in ready mode.
On my 2010, the Service Menu screen was reading 0.7V lower than my actual battery terminal voltage. I would recommend reading the battery terminal voltage and compare it to the Service Menu screen before making any judgement calls.
