I bought a 2005 Lexus RX300 only supplied with 1 key & it wasn't a master as I found out, big problem if ever lost it or so I thought.
I wanted to blank out all lost keys & remotes to be safe then add new keys/remotes, being a 4D transponder inside remote this will be locked to the 1st car it's added to, so if deleted you can't re-program it to any car again.
I purchased a Lexus toyota smart key maker (online) to add new keys bought from Lexus directly, the keys being 3button remote with 4D transponder inside
With my only key in the ignition so not to blank it from the ECU IMMO
I pushed the smart key maker into OBD2 port under drivers knee holding the button until I heard beeping sounds, (THIS BLANKED ALL KEYS I DONT HAVE) putting ECU IMMO into enrollement mode ( looking for new keys needs 3 keys coded to stop this) I then removed key maker & was able to start & drive with existing slave key, the security light not working as should was telling me it's in enrollement mode, I took my 1st new key inserted into ignition for approx 8sec then my 2nd new key after 5 sec security light was off tested all keys started car ok, then programmed remotes to lock unlock doors, job done. Using a t300+ Obd2 tool I now Have 2 new master keys & 1 original slave key working on my car😃