Prius Complete Shutdown (Almost)

Yes there are ways to test all 28 modules, it's called load testing. You can test for remaining capacity and it'll give you a good indication of how strong the module is.

But yes, all that stuff takes time....time is money. Module swaps are easy and cheap, less time, less money, more headache.

 

Getting a new battery from Toyota is the medicine you don't want to take so here's something that might sugar coat it: you'll get more for your car when you do sell it (and advertise it with a genuine Toyota battery) reducing your overall costs.

 

I'm going to send you a PM, gonna help you out here

 

DTC P0AA6 means that the high voltage system has a ground fault somewhere. The high voltage wiring is isolated from body ground for safety reasons.

One of the ECUs has a system that is able to detect when ground faults exist. When a fault is detected, P0AA6 is logged and the car will refuse to start.

You can temporarily work around this issue by disconnecting the 12V battery for a few minutes to clear the ECU memory, as you've already discovered. Then the car will start once. This causes no further harm to the vehicle but you are exposing yourself to a safety hazard by driving the car in that condition.

The ground fault may be in the traction battery and if so is likely due to one of the 28 modules leaking electrolyte which allows electricity to flow to the body ground. A temporary fix is to identify and replace that module with a used unit. As other posters pointed out, the longevity of that fix may widely vary. One way to determine the ground fault is in the traction battery is to measure voltage from each high voltage lead to ground at the battery, after disconnecting the high voltage cabling leading to the inverter. If any voltage is measured that is evidence of a voltage leak within the battery.

The ground fault also can be in any other component exposed to high voltage: traction battery ECU, battery cabling leading to the inverter, inverter, transaxle, AC compressor.

IF the traction battery is the problem (which has not yet been definitively established) the best solution is to replace it with a new Toyota battery.

The next best solution would be to replace the 28 battery modules with 28 used modules from a newer Prius (2010 - 2015 model years) that had been totaled in an accident - if you can be sure that the 28 modules all came from the same vehicle that was working fine prior to the accident and are not rejects from a variety of vehicles. Each module has a serial number and you would expect to see them listed in sequential order when examining a battery case that contains original equipment modules.