The 4WD system is always active and requires no driver input. It is capable of handling all road conditions, including street and highway driving as well as off-road and winter driving. If the vehicle is equipped with the low range option, the driver can optimize more 4WD control by moving the terrain management switch for the correct terrain. See Off-Road Driving (page 193). Note:A warning message will be displayed in the information display when an 4WD system fault is present See Information Messages (page 80)..
A 4WD system fault will cause the 4WD system to default to rear-wheel drive only mode. When this warning message is displayed, have your vehicle serviced at an authorized dealer. Note:A warning message will be displayed in the information display if the 4WD system has overheated See Information Messages (page 80)..
This condition may occur if the vehicle was operated in extreme conditions with excessive wheel slip, such as deep sand. To resume normal 4WD function as soon as possible, stop the vehicle in a safe location and switch the engine off for at least 10 minutes. After the engine has been restarted and the 4WD system has adequately cooled, the warning message will turn off and normal 4WD function will return. Do not use a spare tire of a different size other than the tire provided.
If the mini-spare tire is installed, the 4WD system may disable automatically and enter rear-wheel drive only mode to protect the driveline components. This condition will be indicated by a warning in the information display See Information Messages (page 80).. If there is a warning message in the information display from using the spare tire, this indicator should turn off after reinstalling the repaired or replaced normal road tire and cycling the ignition off and on. It is recommended to reinstall the repaired or replaced road tire as soon as possible. Major dissimilarity in tire sizes between the front and rear axles could cause the 4WD system to stop functioning and default to rear-wheel drive or damage the 4WD system.
http://www.fordservicecontent.com/Ford_Content/Catalog/owner_information/Everest_U375_TEC_Australia_2015.pdf