One problem related to o2 sensor has been reported for the 2014 Ford Focus. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2014 Ford Focus based on all problems reported for the 2014 Focus.
The engine light came on stating that it is a O2 sensor issue. I've replaced the O2 sensor several times. I've had mechanics and the dealership look at it with no ability to figure out what it is. It is believed to be electrical, most likely the wire harness. My alternator was affected as well by this electrical issue. I have had to put in a few new O2 sensors, two new alternators, and a battery.