Can Enginer kit kill 12v Prius battery?

I have never seen the Enginer system kill a 12V battery, since it can only draw power from the Prius when the Prius is on and READY.

Chances are the 12V battery might have been due to be changed anyway. The Prius 12V battery must be healthy to ensure proper diagnostics.

I always recommend the Yellow Top 12V replacement battery from Elearnaid.
If you are in the LA area, they can even do the installation for you.

Now about the transaxle, did the dealer give you Techstream printout with the exact error codes (and subcodes if any). If not, ask them for it...you paid for a diagnostic, you should get detailed report of the troubles.

Share the codes with this forum for a 2nd opinion.

 

Not that far??? (I used to live in Nor and So Cal.) Luscious Garage is 382 miles away from Pasadena. (6 hour, 25 minute drive per Google Maps, w/o stopping.) That's 614 km. That's like asking you to take your car from Amsterdam to Berlin, Germany to get it fixed.

Even if LG fixes his car, the OP will then need some means to get to LG to drive it back. If not fixable for a reasonable cost, he's got to deal w/the consequences of a car being almost 400 miles away...

 

But looking on the bright side, they will probably know what's really wrong, and at a savings of about $4000, or $10/mile, it could be well worth it.

Also, I too find it extremely questionable that it is the transmission, if for no other reason than the fact that transmission failures are so rare. Why not tell them, not ask them, tell them to put in a new 12V battery if the OP doesn't have the ability to do it, and see what happens? When you can do things yourself too, a person could just swap in a known good 12V battery and see if that is truly the problem. Oh, and if the dealer swaps 12V batteries, I would be standing there watching them, and get the one taken out.