2006 Lexus GS 300 Owners Manual - Page 656

KEYS AND DOORS The electronic keys are required to deactivate the engine immobilizer, and are essential for the engine immobilizer to function correctly, so be careful not to lose these keys. If you make your own duplicate key, you will not be able to cancel the system or start the engine. To protect items when using valet parking, turn the trunk lid opener main switch to inoperative or lock the glove box if necessary, and leave the electronic key (with the mechanical key removed) with the attendant. For details, see "Trunk lid opener main switch" on page 130. If you should lose your electronic keys or if you need additional electronic keys, duplicates can be made by a Lexus dealer using the key number. We recommend writing down the key number and storing it in a safe place. 10