I have an AVIC F90 WITHOUT a reverse camera installed. All of a sudden, every time I turn my car on the "CAUTION - IMAGE MAY APPEAR TO BE REVERSED" black screen comes on as if it were reading a lead from a reverse camera, yet I don't have one. The image doesn't go away and the Menu and Map button become disabled and can not be used. I've tried pulling the unit out and checking all the wires to make sure there is no contact of any kind on any of the camera leads and sure enough there wasnt.

I am lost.

Some how your camera polarity was switched to view the in-reverse image full time. Put your car in reverse and then go into the settings and change the CAMERA polarity from its current setting.

Problem solved! Thank you.