I just bought a used 2005 ES330 and it only had one master key and a flat key with no case. How does one find out what their key number is? The manual states I need the master key and the key number to have the Lexus dealer make a new one with transponder chip. A valet key would also be nice for when I have it serviced.

 

My 03 ES300 only came with one key so I found an uncut replacement key blank on Ebay and took it to a locksmith who had a laser key cutting machine. After he cut the key I tried it out on the driver's door and it worked fine. I also found an old Lexus (might have been Toyota) key on Ebay that had the same transponder as mine (check the number on your key), and took the transponder out of the old key and put it in my newly-cut key. I then scoured the internet and found directions to get my car to accept the code(s) from the transponder in the new key. Took me a little bit of time to do but was way cheaper than what the Lexus dealer wanted to do it.