I have a 2003 Ford Excursion that is having an odd mechanical problem. When I turn my left blinker on, both of my back lights flash. The dash (radio and mileage indicator) flash too. It has the identical behavior to when the emergency flashers are on except the dash still shows the left blinker is on. The right blinker works as it should. Any ideas of what might be wrong would be GREATLY appreciated!

 

does the vehicle have a tow package,if it does check the harness that connects to a trailer for damage.