The contact owns a 2016 Ford F-150. The contact stated that while driving 20 MPH, the transmission downshifted to a lower gear while attempting to stop at a traffic light. The check engine and the service engine warning lights were illuminated. The contact stated that the transmission occasionally downshifted unexpectedly. The vehicle was taken to an independent mechanic however, the vehicle was not diagnosed. The independent mechanic was unable to duplicate the failure. There were no warning lights illuminated at the time the vehicle was taken to the independent mechanic. The dealer was not made aware of the failure. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 112,000.