This was me. While my battery was connected it was showing good voltage (even while cranking), but after checking everything and not seeing much of a draw anywhere, I disconnected the battery and it said I only had 9 volts.😄(n)
I had this fault code this last weekend. I had to replace my battery. Once I had a new one in, it fired right up!
I tried starting it with jumper cables and then charged the battery overnight (Which said fully charged in the AM) and nothing.