I started this is another thread because I would like some input. Our 2006 Prius Navigation System Owner's Manual, page 102 shows the Display screen as having a Day Mode option. Yet our 2006 Prius does not have this option. Our 2007 Prius does have this option. Toyota Customer service says the 2006 should have it. Our dealership is stumped and while they agree the manual states the 2006 should have it they say a used 2006 on their lot doesn't have it.

Night mode for our 2007 changes the background color in the NAV display to black. Day Mode would make it a dimmed white, which is all our 2006 does. It doesn't show a black background with the headlights on.

I love to hear from anyone else with a 2006 to see if you have the Day Mode option in the Display screen.

Fixed it! After a few more calls with my dealership we found the issue. The dash dimmer switch was set all the way on. Once we set it to a little dim and turned on the headlights, the Day Mode option appeared. What a relief!