Hi robert,
How did you go with that code? My RXT is 260 2010 is doing the same thing and wont go faster than about 6okph. Top Gear Frankston haven't heard of it before.
It turner out to be a faulty cooling sensor. They replaced it and all went well. Now the OTAS light come on! I can't seem to win. Also the seat has mould on it so they are replacing it under warranty.