2005 Prius - ABS, VSC, Brake system, master warning light all on, no codes.

P0AA6 HV isolation fault most likely. It's the only RTOD HV fault that will allow you to continue driving the car normally after it triggers, UNTIL you turn it off. After that, it will not allow the car to go to ready mode. The only way around it is to reset the code, which is what you did by disconnecting the 12v battery. The code readers that were used apparently did not speak 'Toyota hybrid language", so didn't recognize the codes. Wouldn't be the first time....

Frequently caused by electrolyte seepage from a HV battery module, but could also be cabling, inverter, transaxle or even the AC compressor circuit. If anyone you know has techstream, look under Hybrid Live for 'shortwave highest value'. This is a 0-5v measurement of the quality of the 'insulation/isolation' between the HV system and the chassis of the car. 5v is perfect, 0v would be a dead short. I think (iirc) a P0AA6 triggers around 3.2 volts. The vast majority of cars in good working condition are >4.9v

The P0AA6 will also have a subcode available in it's freeze frame data. that subcode can help determine which section of the HV system the fault is located.

But I may be wrong....wouldn't be the first time for that either....
and after actually looking at the photos, that's a lot of warning lights. Maybe even more than I remember kicking on for a P0AA6. Will be interesting to see what codes you actually have. Will be important to get them read by a Prius capable scanner. That should be the first step, helps you to avoid all my BS guessing...

 

It doesn't show any codes for anything but the infotainment gadgets. No use for the brakes or powertrain.

If you don't have an OBD-II scanner, you can get the brake codes out (in abbreviated 2-digit versions) with a short piece of wire, by counting blinks of the dash lights.