I was able to program the remote portion (FOB) of the key, but the key itself won't start the car.
Here's what worked for me to program the remote control potion of the key:
1. Get into GX470 and make sure all doors are closed and locked.
2. Insert registered master key into ignition to turn off blinking security indicator on dashboard.
3. Remove registered master key from ignition.
4. Unlock and open driver’s door and keep door open.
5. Within 5 seconds – Insert and remove the registered master key from the ignition switch twice.
6. Within 40 seconds – Close and open driver’s door twice
7. Insert and remove the registered master key from the ignition switch
8. Within 40 seconds – Close and open driver’s door twice.
9. Insert the registered master key into the ignition switch and close the driver’s door
10. Switch ignition ON and OFF only ONCE to program a key remote transmitter code while retaining the key original codes.
11. Remove registered master key from ignition switch – System should now lock and unlock vehicle once to indicate success or twice to indicate failure. If it fails here, then go back to step 1.
12. Within 40 seconds – Press and hold LOCK and UNLOCK buttons simultaneously for 1.5 seconds.
13. Within 3 seconds – Press and release LOCK or UNLOCK button. System should now lock and unlock vehicle once to confirm registration, twice to indicate registration has failed. If it fails, then try step 12 again until step 13 verifies success.
14. Within 40 seconds– Repeat button procedure to program remaining key remote transmitters
15. NOTE: To exit programming mode you can open driver’s door or insert ignition key. Also, note that a maximum of 4 key remote transmitters can be programmed.