Red triangle but good mpg

More than likely you have the hybrid isolation fault this requires you to clear the code to generally drive the car starts and drives normally charges relatively normally gets pretty normal gas mileage and so on

 

What are the trouble codes that are being cleared? List them, and you will get some answers about what the problem is with the car.

PS, do not buy an old Prius unless you have experience fixing cars. Old hybrid cars can be very expensive to fix if you can not do the work yourself.

 

The P0AA6 code is the ONLY (hybrid system RTOD) code that will allow you to continue driving normally until you shut the car off. At that point, it locks you out of going READY, so the next time you need to use the car, you need to reset the codes by disconnecting the 12v battery for a minute. If the P0AA6 is being caused by the HV battery, this can be caused by HV battery modules that are still in excellent condition (capacity wise) but have developed a voltage leak to the steel battery case. Sometimes this is caused by electrolyte leakage. Sometimes it is caused by microcracks on the bottom of the module where the small machine screw fastens the module to the case. The screw threads into a metal insert that is pressed into the plastic body. Sometimes it will develop a crack allowing electrolyte inside to make contact with the insert. Sometimes this can be solved just by putting a piece of electrical tape under that module and leaving that screw out.

If it's a P0AA6, 90% or more of the time it's a battery issue. Can also be AC compressor motor, inverter, cables, transaxle, etc.