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?
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.
Toyota Service Total Failure. So the full story. I bought my Prius used from the dealership. I even bought the extended warranty. I dutifully brought it in for maintenance. My prius cam due for some recall repairs after my maintenance plan expired and i dropped it off. A couple weeks after the recall my check engine light came on. I took it back to Toyota and they said the hybrid battery was bad and it would cost me $6000.00 to repair, and the standard battery was also bad.The said it wouldn't restart on the batteries but would stay running.I was at work so I said no thanks and told them to just jump start it and i'll come pick it up. I took it home and parked it. Because i didn't need it as a primary driver i waited till i had the money to buy the hybrid battery. Some months later I replaced the hybrid battery with the nexcell from DR prius.I replaced the standard battery with an optima AGM. I replaced the key battery. The car still wouldn't start. I hired a locksmith but he wasn't able to program a new key. I took both my original key and a new key bought off line to toyota and they were not able to program either one. they tried new one of their keys from parts with no success. they told me i needed a new immobilizer ECU so i authorized the $2250 for the repair. so they called engineering again and the new diagnosis was i needed another ECU this one for the engine. I said "Have you lost your mind? Yall are just throwing parts at it and don't really have a clue." They asked me if i wanted to continue or just put it back? i said put it back. I now have a non running Prius. Model:Prius Type:Car Make:Toyota Model year:2011 Manufacturer:Toyota Motor Corporation Manufactured in:Japan (Asia) Plant:Fujimatsu Plant Sequential number:356117 Body style:HATCHBACK 4-DR Body type:4 Door Hatchback Brake - front:Disc Brake - rear:Drum Doors:4 Driveline:front-wheel drive Engine series:4-Cyl. 1.8L Electric Assist Engine type:1.8L L4 DOHC 16V Fuel tank:11.90 gallon / 45.0 liter Fuel type:Gasoline Safety restraints:Dual Air Bag, Seat Belts, Knee Air Bag, Side Air Bag-1st Row, Curtain Shield Air Bag-All Rows Tires:195/65R15 Trim level:Base Turning Diameter:34.20 ft / 10.4 m
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.
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.
