I have an 06 IS 250 and this override works everytime. If the nav system has been upgraded to a new version the override may not work, but my understanding is that the override button was gone. I'm not sure why it wouldn't work.
The override, however, doesn't allow you to see radio messages, or use bluetooth features while moving...it only allows full functionality of the gps.
A piece of advice...don't pull the stuff where you write the same message over and over...the moderators will ban you...
Enjoy the site