engine comes on yellow periodically. adding coolant seems to make it go off. to

If the fan is running excessively after the key is off then that is another indication that it may be engine temp./coolant related. If the coolant is low then you should look for a leak both when the engine is cold and after it gets warmed up, as a coolant leak can happen at different temps sometimes. If the engine symbol is coming on then a code will be stored in the cars computer. It should be checked by a professional or at a minimum get a cheap code scanner to check the code yourself. St. Joseph Automotive & Diesel can check it out for you 217-469-2018.