New Prius owner, trans problem?

So, I just bought a beater 2008. The HV battery is shot, but it was at least driveable in a fairly normal sense on the first day that I drove it. Today, it was significantly warmer outside and as I was trying to drive it to get it registered, something went out with a small bang. Now I can somewhat drive it to about 30mph on flat roads. Anything that requires more throttle, such as going faster or uphill and the ICE just spools up while the car slows down.

Read some various things about possibly MG1 or inverter type issues. Previous owner said that the inverter cooling pump was bad, but I only saw battery related codes when I ran a scan.

I ordered a replacement HV battery before this problem occurred, but it is not in yet.

Where's the best place to start as far as the diagnosing is concerned?

 

Update for yesterday. So, it drove to work in the morning fine. Went into limp mode in the mid afternoon when I was driving it to and from the DMV. Then it worked again for almost all of the drive home from work that night. So, it would seem like the ambient temperature is a factor (or a coincidence). Which would explain why it drove fine for over an hour when I was driving it home the day that I bought it. I just received a replacement inverter coolant pump, so I'll probably put that in regardless of whether it is the problem. Couldn't hurt for a vehicle that has 160k miles.

When the problem occurred I was bummed, it felt like a typical automatic transmission failure I have experienced on other vehicles. Then I read about the planetary gears and split drive thing and was relieved. It would seem that if one of the driven elements of the planetary is not providing a load then the engine can't effectively drive the other. If my speculation is right, this is similar to a single tire spinning on a two wheel drive non-LSD differential setup.

The scanner I have is the OBDlink MX currently using it with the torque app. Somebody on this board said it was pretty decent. Although I realize that it won't have all the functionality of a more purpose built scanner, I thought it would be useful for my other cars as well. I don't mind buying the mini-VCI too if that proves necessary. However, it was unclear whether it came with software or if I would need to search the bowels of the internet for some dodgy download. I mean, the battery codes the OBDlink pulled are hybrid codes, but that's probably not exactly what you mean.

 

Well, I replaced the inverter coolant pump which didn't improve anything, as I suspected it wouldn't. HV battery should be in this week, we'll see if that helps.

 

The codes I pulled so far are P0a80 and P3023.

I might be an exaggeration to call it a bang. I was in the middle of accelerating when it entered the hobbled state. Maybe more of a thud, hopefully just some backlash similar to letting off the gas in a manual transmission car. Hopefully, I'll know more soon

 

Yeah, I haven't been driving it since the DMV day. HV battery should arrive today. I'll take a look at adding those displays to Torque, thanks for the tip

 

Finally got a chance to finish up the HV battery swap this weekend. Seems to be driving fine at the moment. Now, onto the other problems...