Thank you!You could write all zeros, but that won't change the functionality, it would just be looking for a key that was programmed with all zeros and that might not even be a valid number to use.
The operational workings are in computer code that is stored in the main CPU. I do think it would be possible to replace the entire unit with a 'fake' unit that didn't connect to a key at all and just told the EFI computer that all is well, keep running. However, this would require reverse engineering the communications between the immobilizer and the EFI computer which ranges from fairly simple to incredibly complex or even impossible.
I didn't understand what you meant about matching the new ECU? What I proposed above is basically duplicating the key codes in the working ECU into the non working one, that should be possible, but it does involve messing with the working one and running the risk of damaging it.
A new ECU with three keys and an ignition lock cylinder was part number 89703-60020 and listed for 424 euros. I'm not even sure this part is available from Toyota any longer.
That answered my question exactly!
Yeah, I started down the same path you had already stated about the new ECU.