2002 code 3120

I just picked up an 02 and it had been siting for around a year. I bought it from a guy who had a minor front end collision and decided to do the repairs himself. Unfortunately shortly after getting it back together he lost all the coolant while driving it. Apparently he continued to drive it and the HV battery was run down enough to make it unable to start. He brought it to the dealer and after they charged the battery they said it needs a battery, inverter, all the wiring and the trans!! Who wouldn't sell it if they were given that estimate!!

So this is what I have to work with...
Of course I don't know if all of this story is true but I do know some of it is at least. No coolant was visible in the radiator. The repairs were obvious from the collision. However, I do have all the paperwork showing everything from the first oil change in 02 to the accident in 2010 and even the last dealer diagnosis.

When I got it back I first checked the 12 volt battery and it was good. The inverter coolant was full and the pump was operational. The traction battery was dead. I replaced all the HV modules from another battery that were in good condition. Got it all back together and when I turned the key all I got was a loud thunk and it wouldn't turn over and got a 3120 code. Unfortunately, I don't have any way to get the information codes but i certainly don't want to just put a trans in it cause of this code. It seems form what I read here is that with this code I will most certainly have to replace the transaxle.

 

Today I checked to see if the ice was ceased and it spun freely. Car moves fine in neutral. Does anyone know if a high end snap on scanner will retrieve information codes?.