Make car forget smart key?

Sorry to hear that you lost a key.

Invalidating all of the keys, and then programming the existing keys is likely your best bet.

Fwiw, you're likely better off having a dealership do that.
Otherwise, you can easily end up with a brick in your driveway, that then has to be towed and dropped off at the dealership.
Make sure you bring a printout of your registration, along with your driver's license.

Good Luck!

 

I'd call the dealer- and tell them what happened and ask what they need you to provide.

Mike

 

The basic premise that's motivating you is best dealt with by doing something to disable the car so if a thief has a spare key the car won't start. You could pull a fuse or add a switch.

As in most Toyota stealerships are going to pretend that wipe and re-seed of remaining FOBs is not an option and that you need to replace the entire immobilizer for many thousands of dollars all for something that's likely not to happen.

Alternatively you could get an electronic locksmith with Toyota Techstream software w/monthly security upgrade to wipe and re-seed your FOBs for under $1K but that's still a huge amount of money to throw away to prevent something that's likely not to happen.

Or you could buy a mini-vci dongle that comes with Toyota techstream and install on old Windows computer and use the service in Europe that charges you ~$40 for turning your VIN# into the wipe and resead password in Toyota techstream.

 

As long as you still have one key that works, there is absolutely zero need for any scary "wipe and reseed" or "replace immobilizer" nonsense.

"Car, please forget every smart key except this one here that I'm using" is one of the routine registration procedures. Any dealer can do it, or independent locksmith or anybody else with a Techstream rig. You don't need the more-restricted "security professional" activation, or any kind of seed code. Those things are only needed (for obvious reasons) if you are trying to start with no currently working registered key.