Immobilized ecu dead key fob

I think you are dealing with mechanics who are not very good. I believe a pre-existing fob usually can not be reprogrammed from scratch but a new one can if you still have another good one. Otherwise they wipe everything and start with new fobs. I am going by what I have read in the past, not personal experience.

It could be the locksmith fouled up the sequence and then had to sell you a new fob. Its not clear what you meant by "they couldn’t program my old key my new used cleared key." Old, new or used cleared fob?

You could check The Care Care Nut youtube channel. He has a recent video about programming fobs.

 

It's not an ecu problem. It's and "OE". Operator Error.
Apparently they don't know how to program a key.
I hope you had them reinstall the original ECU and refund your money.
They told you that would solve the problem, and it didn't.

 

Wow. What a mess. I think the mistake was the assumptions made after the dual battery diagnosis followed by parking it.

At that point the high voltage battery was still functional. All the car really needed was the 12v battery. The hv battery can't be totally dead and still allow the car to run from the dealer to your house.

However the hv battery could have been weak in a ten year old car.

From that point on its hard to say what happened. I would revisit the diy hv battery swap, a significant job that could have a missing step, cable, nut or even an orange plug not completely pushed in, a three step process often responsible for a no start. I would verify the new 12v installation and voltage. Most likely many 12v jump starts have occurred, I would check the 125a fuse in the engine fuse box which instantly blows on a reverse polarity jump.

The keyfob was ok when you parked it, I suspect its failure was a guess or perhaps a misdirection because the car would not go Ready. Its possible the locksmith or subsequent dealer attempts on this cleared the existing fob registrations. To add confusion, in your first post you said the locksmith started the car, in the second he failed?

At this point there have been so many hands on the battery and control systems that multiple problems can exist, a situation "good" mechanics have trouble with. You need to find an expert diagnostician on a Prius. I would expect a dealer would be the place, maybe not in your case based on the "full" story.

 

Did you ever get the car fixed Im having the same kind of issue?

 

you need new batteries and ecu's? might as well total it

 

When you power up the car do you try to start it with the brake pedal pressed first try?

When you replaced bad batteries, you need to push the start button twice without pressing the brake pedal.

The system needs to recalibrate the ecu's
Once that is done then power down and then try starting it normally with brake pedal pressed.