How it works
During programming the car's key memory is cleared, then the new key and any keys you still have are added back. Anything not present is gone from the list.
Bring every key you still have
Keys not present when the list is cleared stop working. If you have a spare somewhere, bring it so it can be added back.
The door blade
Erasing stops the engine from starting with the old key. The door lock is mechanical; on some cars the old blade still turns it. Rekeying the door lock covers that.
Written by Need Key, the lost car key service of Keyhub Locksmith in Marietta, GA. Updated October 24, 2026.