Like everyone else, I had the same prob about 6 months ago.
The Wrench Light indicates a prob with the electronic throttle control system. Most likely the prob is the throttle position sensor not giving the computer the info it is looking for. As you all know the car is drive by wire, the computer has complete control over the motor. When you push on the gas petal you are only asking the computer for more power, the computer looks at all the info coming from the motor and traction control/ABS system and then decides how much power to give you by way of the throttle body. It then looks for conformation from the Throttle position sensor to confirm that everything is going as planned. If the TPS is giving a bad reading then the computer indicates a problem (wrench light) and may or may not go into limp mode. Now for the frustrating part, when you turn the car off and on again, the sensor resets itself and all is good, for a while! When you go to the dealership tell the service manager that you are having an intermittent problem with the electronic throttle control system and they need to test the throttle body for a faulty TPS. The throttle bodies on our cars are sealed and non-serviceable and must be replaced.
I feel you pain as this happened to me while driving through heavy rush hour traffic and going into full limp mode at speed, twice!!
I hope this helps.
2012 F-150 EcoBoost 4X4 (work truck)
Focus S #1, Sedan Revolution #192, Rally Revolution #8, March 2012 SOTM
Focal Distortion, a Ford licensed club and FSC member.
Sgt, USMC (1999-2003)