2009 Prius 248000km Death triangle no codes

Error code P0A84 is " Hybrid Battery Pack Cooling Fan 1". So, the cooling fan for the hybrid battery is not working correctly, and the hybrid battery is overheating. This makes sense based on what you wrote in post #13.

That code is very common on a Gen 2 Prius because of water seepage into the hatch area and onto the fan electrical connector. The connector gets corroded, and the fan does not operate.

I recommend that you get the Autel AP200 scanner working because there may be other codes that the Dr Prius app can not read. Follow the instructions in post #17.