Where to start…

Your HV battery is no longer isolated from the rest of the car what that means is now you're pushing DC voltage from the high voltage traction battery to the frame of the car which is where your 12 volt system grounds to so you're 12 volt system has nothing to ground to it's getting live voltage from the HV battery pushed into the 12 volt so then you're can bus system in your car which all your communication of your computers and wiring and everything works on is having humongous problems and not liking life because it can't ground to a good ground it's trying to ground to alive chassis which is getting anywhere from 0 to 130 DC volts or even more to the frame of the car because you have the hybrid isolation fault The battery is not isolated from the rest of everything in the car then in your picture that's a relay that that wire that's burnt is on top of and it goes back to the battery and the other wire on it runs up to the front of the car to the inverter so there's two orange wires coming off of the two relays under the battery cover that shoot up to the front of the car and plug into the inverter and then the other ends of those wires go back to the battery pack so when you get the battery pack completely uncovered take the cover off you'll be able to take a picture of it and trace the wire where it's going from the relay to the battery pack and see where it nuts on to a battery post or a connector and I'm sure when you go to looking at this you're going to see all kinds of corrosion and nastiness and all of that that needs to all be cleaned up before you're going to get anywhere with the starting and any of that business and that's going to take you some time and a little bit of money to get all that done after the 3-year sitting all that you may want to look on Facebook marketplace and find a private guy who likes to rebuild batteries they're all over the country these guys I have a guy here that'll take and build me a battery for like 480 bucks and does a very good job too as matter of fact. Or you can go buy you a new battery for three grand from the Toyota dealer or whatever it is now I wouldn't do that unless I knew the car was worthy of that kind of money A car this old can be worth that kind of money if you're going to be able to use it and drive it for 4 or 5 years or better this model should be able to do that everything else being reasonable.

 

The P0AA6 trouble code will stop the car from going into "ready". Try disconnecting the negative 12v battery cable from the battery, wait a couple of minutes, and then reconnect. If the 12v battery is still good, the car will probably go into ready.

You need a good scan tool to read the freeze frame data for the P0AA6 code so that you can get the three digit INF code for troubleshooting the location of the high voltage leak. Seach this forum for P0AA6, and you will find much information that will help you.

 

I've seen damage on a main relay similar to that. It was caused by a loose fastener, allowing HV battery current to generate heat at that point of high resistance. The lug on the main cable should clean up just fine. The relay may or may not, but they're easily available on ebay, etc. 100% chance the battery itself has several, if not all 28, dead modules after sitting 3 years. The battery ecu is also likely damaged at the pins from corrosion, and will likely need to be replaced. The P0AA6 would likely clear with battery replacement/repair.

 

All of the High Voltage stud connections should be tightened to 48 INCH pounds. If all of the 28 HV battery modules are within 0.3V of each other, then you have a shot of seeing if the car might run. 200V is close to the minimum.

Clean the engine throttle body. The gas is old and might cause problems (it is very difficult to siphon the tank out - I usually try to disconnect a fuel line - connect a hose to a "waste" fuel can and jumper the pump relay).

It is not uncommon for injectors to clog or stick shut.

You have to perform 3 steps to refit the orange HV fuse - push it in, fold the lever in, then slide the lever down.

The P0AA6 will cause a "no ready" condition on the 2nd start attempt. For testing you can clear codes and try to run it.

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Unfortunately, that implies 1/3 of the modules are showing less than 7 volts. It's going to be interesting to see what happens, but don't be surprised if the battery condition prevents the car from trying to start. If it does make an attempt, I just worry the large current surge will immediately cause the voltage to drop wayyyyy down, even on the higher voltage modules, and the main relays to go open. If that happens, hopefully throwing a bit of charge into the modules will cure it.