Here is the instruction on adding another key for Lexus GS300,400,430 from 1998 to 2005 in case someone seek the solution. Twp parts, key and remote programming.
1. Close and lock all doors. Unlock and open drivers door.
2. Put key into ignition and remove. Do not turn it on.
3. Using the electric lock switch. Lock and unlock 5 times. (Lock, Unlock, Lock, Unlock, Lock, Unlock, Lock, Unlock, Lock, Unlock)
4. Close and open drivers door.
5. Using the electric lock switch. Lock and unlock 5 times. (Lock, Unlock, Lock, Unlock, Lock, Unlock, Lock, Unlock, Lock, Unlock)
6. Put key into ignition. Turn to “ON” , turn off and remove.
7. You will see the door locks cycle by themselves.
If the door locks do not cycle (lock and unlock) by themselves then the car isn’t in programming mode and you must start over.
8. On the remote, press and hold the LOCK and the UNLOCK button at the same time for no more than 2 seconds.
9. On the remote, press the LOCK button for no more than 1 second.
AT THIS POINT, the locks should cycle by themselves ONE time. This means the procedure was accepted.
IF the locks cycle twice it has failed.
The most common reason for programming failure is because the car didn’t receive a good signal from the remote. To fix this problem try these tips.
1) Stand outside of the car while you are performing steps 8 and 9.
2) Don’t hold the remote buttons down as long.
As long as the car is still in programming mode you can keep trying steps 8 and 9 until you complete the programming. If you wait too long and the car exits the programming mode then you must start over.
After you get the remote to program then continue on with step 10.
10. Close and open door to end programming procedure.
1. Insert an already programmed master key into the ignition. Do not turn.
2. Press and release the gas pedal 5 times.
3. Press and release the brake pedal 6 times.
4. Remove the key from the ignition.
5. Insert the new key you want to program into the ignition.
6. Press and release the gas pedal one time.
7. Wait 1 minute. The security light will be blinking for this one minute. When it stops blinking your key is programmed. To end programming step on brake one time.
NOTE: Look for your security light. This light will guide you during the programming procedure. The security light will go off at Step 1. It will remain off until Step 6. The security light will come on and start to blink after Step 6 until the key is programmed. If the security light comes on after Step 4 STOP the procedure and start over again.
If you perform this procedure too slowly your car will not go into programming mode. If you can not get your car to go into programming mode make sure you are using a master key and not a valet key. If you have a master key then you will probably need to perform this procedure more quickly.