The key with the remote keyless entry to my 2010 Base Fit was stolen. When I go to the dealer or locksmith to have it replaced, will the old key, still in the hands of the thief, still work? Or will they reprogram the new key and the ignition so only the new key works?

I heard the latter from the dealer, and the former from a locksmith. Many thanks for your words of wisdom.

 

If you let the service writer and/or tech know that a key was stolen, the stolen key could be deleted from the vehicle's Immobilizer system and be almost rendered useless. The reason I say almost is due to that AWOL key (be it missing or stolen) is still able to LOCK/UNLOCK the doors via the door lock cylinder but WILL NOT disable the alarm thus causing the alarm to trip. If you do recover the key later, you can have it programmed to the car again later.

 

The old key will still work in the lock, and turn the ignition, however when they program your car with the new key they should delete the old key's electronic signature so it can't start the car.

Be sure to bring in all keys you have so they don't delete the wrong one.

 

On the other hand, if you replace the cylinders and keys, you can render the missing key completely useless.

Can be worth it for piece of mind (if you know for sure key was stolen, and not just "somewhere" at home), knowing they can't get into the car at all.