Maintenance Mode Basic Diagnostic Procedures for P0A80 Replace Hybrid Battery Pack.

If the car has sat unused for a while, it's very likely there's just a module or two that have self-discharged below the trigger threshold for coding out. Will the car start and go to READY condition? If so, I would fire it up, force charge the battery and then turn the car off. Then disconnect the 12 v battery to reset all the computers to default, reconnect the 12v battery and start it up again. Drive it and see what happens. It may take that battery sitting for months, unused, for those modules to self-discharge enough to cause a problem. Or it may be overnight. Only way to tell, without disassembly, is to try.

on another note, I've had very good luck rebuilding the Dorman Prius batteries. Typically, even when failed, they only need one or two modules replaced and then they're good for years again. Wire harnesses have always been in excellent shape, they always have nickel plated busbars, always have great condition ecus with no corrosion, etc.

 

If you can search around in your area in Florida and find somebody with a 300 volt DC charger like the Venice hybrid charger system there are others if you can get the cover off the battery and hook it up to the battery side connections turn on the charger and watch the display on the Venice charger you will see the battery charge and then it will show you the amount of voltage you're putting to the battery I usually am using the 300 volt setting and then I watched the battery voltage rise and when that voltage rise no longer changes in a 5-minute period It's recommended to turn the charger off put your cover back on if you do that sort of thing or start the car up and take it for a spin now take a look at your readings while you're driving with Dr Prius or whatever it is you use see what you get I bet you'll get a drivable car pretty quickly I've done this four or five times now with cars that are sitting in the weeds. If you learn anything from any of these Prius sites it should be that Prius do not do well sitting If you are not driving the vehicle get a Yaris get a Corolla hand off the Prius to somebody that will drive the car not park it out in front of their town home and use it to go get groceries every eight days and you'll be golden If Dad's not going to drive the car you'll be spending a lot of time helping out for the next few years try and edge him into a Yaris or Corolla heck a sienna van . Prius are not happy sitting EVER..

 

The OP has a thread that he started 1 day ago for this same car. Take a look at the thread linked below for more history about the car's problems and what was done to try to fix it: https://priuschat.com/index.php?posts/3446289