How to reuse old Prius fob with different Prius

Question

I had a 2007 Prius until it recently got totaled, and I replaced it with a 2008 Prius.

I'm now trying to pair my old 2007 key fob to my 2008 Prius.

I've followed these steps (also pasted here),

1. Open the driver door and leave it open with no fob in slot.
2. Insert old fob into slot and remove it twice.
3. Close and open driver door twice.
4. Insert and remove old fob once.
5. Close and open driver door twice again.
6. Insert old fob in slot and close door.
7. Without pressing the brake, press power button, wait a second, press it again, wait a second, press it a third time to turn car back off.
8. Remove old fob from slot.
9. 9A) Press and hold the Lock and Unlock key (simultaneously) on the OLD/MASTER fob.
10. 9B) Press both the Lock and Unlock key (simultaneously) on the NEW fob. Hold for about 1.5 seconds. Then execute this step again.
11. 9C) Within three seconds, press the lock key on the NEW fob.

It seems to work until step 9C, where nothing happens.

Is there anything I might be doing wrong that would cause 9C not to work?

Or is re-pairing my 2007 fob to my 2008 Prius completely impossible because the fob itself is no longer fresh and identity-less straight from the factory?

Thanks so much for your help.

Answer 1

It seems like my old 2007 Prius fob successfully paired to be able to drive the car but cannot unlock the doors of my 2008 Prius.

https://mechanics.stackexchange.com/a/12980/21953 and https://priuschat.com/threads/programming-an-extra-fob-for-2008-prius-success.48079/ seem to agree.

So what I've done is switched the metal keys so that my 2007 fob now houses the metal key that fits my 2008 Prius (and is able to unlock the doors).

My 2008 fob is able to open the doors (as long as its battery is fresh) and start the car.

My 2007 fob now contains the metal key that can open the doors, and the fob itself is able to start the car.

Answer 2

The only time that s Prius smart key can be fully reused, occurs when you have lost all keys and must re see the immobilizer. At that specific point and only at that time you may register up to 2 previously used keys

Not that the keys fcc id, model number, and another number i can't remember must all match.

PS: You may be able to re seed your immo with your old seed. No guarantees tho.

PPS: I found and read the specs on these keys, that's how.