Gen 3 2011 Prius My 12v battery died when I replaced it my key wouldn’t start the Prius. I replaced the battery in the key and the car wouldn’t recognize the key. I hired a locksmith to program a new key but he couldn’t get it to take. He was able to clone my key with a cloning tool and start the car. Still he couldn’t get new keys to program. I took it to a Toyota dealership and they couldn’t program my old key my new used cleared key. The tech said I needed an ecu. So I had them install a new one at the cost of $2250. Well that one won’t program either. And now they are talking about maybe having to replace other ecus. Is there any reason the transmission ecu would need to be replaced in order to program a key?