Argh! P0A090 problems!

So, I've had this 2007 Prius for a couple years now, and 3 times in that time, I got the P0A090 code with my generic OBD code reader with Torque Pro, but each time I did not get the extended code, as I was on the road, and my laptop with Techstream was at home. Had to reset the code with Torque, so can't read a code with Techstream later if it no longer exists. Each time it happened, I was about 20 miles into a 30 mile commute home from work, and it happened when I was accelerating up a fairly steep grade. It seemed that the first time, the electric motors shut down and I limped to a stop in a barely safe place and the engine barely ran, even with keeping the throttle floored. The last time it happened, it seemed that the gas engine shut off and I was only running on electric motors. Again, had to do code reset with Torque Pro, and again, no codes when I got home to use Techstream. I've looked over the back end of the car pretty well, inspecting all the connectors and wiring in back, including overhauling the traction battery itself, charging/balancing, etc. I'm an electrician, experienced in extreme high voltage systems, where I work at a large power HVDC substation that converts AC into DC and vice-versa, basically a huge version of the Prius inverter pack, but at 500kV-1MV instead of 200-500 volts. Our one-line diagram of or plant is surprisingly similar to the diagram of the Prius' inverter. Except for also involving two motors and a gas engine. Anyway, since it's an intermittent problem, I'm not sure how to troubleshoot this one without having the extended code from Techstream. Where do I go from here? Drive it until the code comes back at a really inconvenient time a few months from now? Will the transaxle be damaged (further?)?

 

Thank you for the two workups, but my car's issue is P0A090, not P0A09. According to the FSM, two very different problems. 09 is in the inverter, and 090 is in the transaxle itself, from my understanding of the FSM. Are these workups directly out of the FSM, or are they from TSB's or somewhere else? Meanwhile, I guess I have to wait for the RTOD to return so i can actually use Techstream and get the extended OBD code so I know better how to proceed. This car goes months between RTODs and my wife is afraid to drive it now, and is worried that if I use it as my daily driver until the next RTOD, I may damage the car further. But I also don't want to just tear the car apart looking for ghosts and waste a LOT of extra time and risk other damage too. And it's winter and car won't fit in the garage. I may just go ahead and pull the inverter cover and start by meggering the windings on MG 1 and MG2 for lack of a better plan. That seems to me a pretty safe and simple test I could start with. I'll have to borrow a megger from work, or do that at lunchtime at work or something.

 

Yes, Factory Service Manual.

 

Is your trouble code P0A90?

What is "FSM"?

Apparently some scanners report P0A090 and P0A90 as same thing. But P0A09 is definitely not the same. FSM is Factory Service Manual. I have the PDF of that, 5149 pages.