The contact owns a 2011 Ford F-150. The contact stated while driving at an undisclosed speed, the transmission unintendedly downshifted to first gear, causing the vehicle to lose motive power. The check engine warning light was illuminated. The vehicle was able to restart and reset. The contact stated that the failure had recurred several times while driving. The vehicle was taken to an independent mechanic, where it was diagnosed with an output shaft speed sensor failure. The contact was informed that the transmission lead frame needed to be replaced. The vehicle was not repaired. No further information was available. The manufacturer was made aware of the failure, but no assistance was provided. The manufacturer advised the contact to report the failure to the NHTSA Hotline. The failure mileage was approximately 133,456.