2001 mpv fan/overheating smell/temp gauge
 

I have a 2001 Mazda MPV with 90,000 miles recently it has started to have an odor like it's overheating while driving or while turning the vehicle off it seems to be running rough and it is getting terrible gas mileage I went to AutoZone and put the code reader on it and the code reader cannot pick up the vehicle so I'm trying to figure out how to dress this issue it doesn't appear to be losing fluid but I have a feeling it's the temperature gauge that is just staying in the same position not giving an accurate reading any suggestions would be greatly appreciated