Your dash dimmer needs to be bturned slightly back from all the way to the right, you should hear a little click, you also need to be in a darkened area so the sensor on the windscreen accepts it as being dark and then you should have the icon on the nav screen which is in the middle of two others which is "day" which you will then have the sat nab screen changing automatically which happens just after the dipped lights come on. Phew, at least that's what they told me at my local Toyota dealer and it worked. Hope it does for you.