2012 Eco-Boost F150. Stock.
When I hit the left turn signal it flashes fast. Both front and rear signals are flashing, as well as the mirror indicator. In previously owned vehicles, the fast flash indicated a burnt out bulb, but both are working, just fast. Any ideas?

 

Hmm thats a new one to me.. only thing I can think of is parking light? I do not remember if its the same bulb location or not? Did you check the right side just in case?

 

Do these have a flasher relay still? I imagine so if it flashes fast?

 

Just wondering if both bulbs are flashing in the back.

 

^^^^This, make sure both parking are working and do you have both lights on in the rear flashing. One bulb out in the back does the fast flash also.

 

Also both brake lights?