Red Triangle and Groaning Noise - Help!

I was driving my 2007 Prius and the red triangle appeared, along with the check engine light displayed on my dash, and then a red vehicle icon with an exclamation point on it appeared on my touch screen.

The car started beeping so I slowed down and pulled over and when I let off of the accelerator the car made a groaning noise. I drove it home and connected my ODBII reader to it and it spit out the code P0A78, which seems to have to do with the inverter.

After turning the vehicle on and off a few times, all of the warning lights went off. I drove it around a few times and the lights have not come back on, but that groaning noise still seems to happen every time I take my foot off of the accelerator.

Any ideas?

 

Ok, so I just took it for another drive. The groaning noise seems to happen all the time and gets louder the faster I drive. I got up to about 30 mph and the red triangle appeared again, there was a beeping noise and the car would no longer accelerate. I had to trun the car off and back on in order to get it to go again. I got home and hooked up the ODB sensor again and now there is a second code of P0A90.

 

178,000

 

I was able to get the inf codes for the P0A78 error:

287
604

 

Thanks, I'll try that. I bought the car a month ago. Not sure about the inverter coolant or trans fluid.