I recently tried to program an additional key I bought from Lexus and used the method below. Locks cycled and all but still unable to start the car. This is for a 2000 GS300.. any suggestions?

You can program it yourself. Here are the instructions:

1. Driver's door open and unlocked, all other doors closed and locked.
2. Insert YOUR key in ignition, DO NOT TURN, remove key.
3. Using the lock/unlock button ON THE DRIVERS DOOR, slowly press lock and unlock 5 times (count the lock 5 times and unlock 5 times).
4. Shut door.
5. Open door.
6. Using the lock/unlock button ON THE DRIVERS DOOR, slowly press lock and unlock 5 times (count the lock 5 times and unlock 5 times).
7. With the door open insert your key into the ignition, turn to on position (DON'T START), wait 5 seconds. Turn off and remove key.
8. Locks should cycle once (Car will lock and then unlock once). If they don't cycle or they cycle more than once, do steps 1-7 over.
9. Now using the remote, push lock button, hold for one second, release. The locks should cycle once. If not, start over and go slower.
10. Close the door. Open the door. Press the lock button on the remote. The locks should cycle. Close the door. Press the lock button on the remote, the doors should lock. Press again and the doors should unlock.

Congratulations - You are done!

 

If this doesn't work you may have to flash or replace the ECU. When I was getting a new replacement key, 3 different Lexus dealers advised me that they would program the new key for me but the ECU can only be programed for so many keys. If you are buying a new new directly from a Lexus dealer, Lexus will replace your ECU for free if it has reached it's prgramming limits.

The Lexus mechanic who actually programmed the new key never said anything about it.

Neil

 

There is a maximum number of keys that the ECU will recognize AT ONE TIME. You must have one remaining master key in order to program any new ones. If you have lost some keys but still have one remaining master, the first step is to instruct the ECU to "forget" all other keys besides your remaining master, THEN you can program in a NEW key and not have to worry that someone else has one of your old keys that will still work. The instructions for these procedures should be on this site somewhere. I will look around and see if I can find my instructions for this process.