Many thanks for this post! However it is actually the OPTION hard button on the right that is pushed and held down while the car is running or not. Turn the parking lights on and off 3 times and wonder of wonders the menu pops up. Push "Display Check" then "vehicle signal check" to bring up the mode that reports battery voltage as shown in the photo below. There are a bunch of other things you can check for dash switches, display colors, radio and XM stuff. I didn't spend much time messing with anything other than read the voltage and watch it while varying RPM. Car not running mine reports 12.2 V and running reports 13.6-13.7 V.
Last edited by chunkyda; 07-26-14 at 06:00 PM.