False PA080

Just wanted to post my story to hopefully help anyone that faces the same issue. Here it goes:

I was driving when the engine light came on. I always carry my OBD II reader in case this happens. Upon reading the code it gave a reading of PA080. Since I have a spare battery at home and have fixed 3 others for friends and family I was not to worried.
I arrived home and took out the battery to measure the voltages. To my surprise all voltagea were good. I figure maybe it was corrosion so i tool the module bus harnesses and cleaned both the copper pieces and screws. After reinstalling all i took it out for a drive and after 20 minutes the check engine light came on. Bummer!
Went back home and disconnected the original HV battery and installed the spare HV battery and took the vehicle for a ride. All seemed good when the engine light came on again after 20 min. Remived that battery and all voltages were also good. Now i am scared!
Troubleshooting began first by checking the 12V battery with an ohmmeter and it read 12.4 volts. Thinking this was good I jumped at checking the HV battery including switching the CPU to no avail. In the process I left the HV battery disconnected which gave me codes indicating loss of communication with CPU scaring me even more.
Finally decided to take a break and look around on here and google when I found a better way to test for a week 12V battery. This test required me to let the car sit, turn lights on and press power button twice. If I got a red triangle and message indicating that the transmission sensor was in an abnormal state a weak 12v battery was to blame. So i went put to the car and tried it to my surprise I got the red triangle with transmission message.
So I went to OReilly and got a 12V battery for $170. Came home installed it and took Prius out for a drive. After 30 minutes no Check Engine Light.
So far all good. I drove it to work and back home without an issue. This car has 141k miles and 12V battery was approx 5 years old.

 

i guess after verifying my post over 3 times before posting i still made a mistake. A voltmeter was used. Thank you for the correction.

BTW S Keith, what should the voltage be in the condition you mentioned above?