I am new here and new to Scion. I have an 08 with the navigation and when I turn my headlights on the the map marker is all over the map. With the headlights off it is perfect. I tried searching for this on google and the search feature here but it seems I am the only person with this problem.

 

I don't pretend to know the answer, but if it was a new car, I'd say take it back to the dealer to diagnose and repair. Is this an original navigation HU or something you added? In any case, it sounds to me like there is a power delivery problem, either the alternator or battery is sagging too much under load, and head lights are indeed a serious load.

If it were me, I'd probably first try achieving the best quality battery minus and plus connections I could manage. If that didn't work, I'd suspect the battery, and after that I'd be suspicious of the alternator. When the engine is running, even with the headlights on, I would hope to see well over 12V at the battery positive.

 

It looks like a factory or dealer installed part since it says Scion when the ignition is turned on. Crazy thing is, is that I don't have a book on it in my Owners packet. I have one for the PT546-00080 so somewhere down the line the one I have now was installed. I didn't think about the draw of the lights, so I will check that out.