All fluids could be correct but if the cooling system thermostat or radiator cooling fan is not operating at the right time the vehicle could over heat. The temperature gauge I believe receives its input to the instrument cluster from the powertrain control module via a CAN network. It uses a temperature sensor in the engines cooling system to control air/fuel mixture. If that sensor fails the Check Engine Light would be on. What should be simple may be complex, find a Ford specialist in your area may need Ford enhanced scan tool to diagnose system.