I have a 1990 F250, the temperature gauge always reads hot and the check engine light will come on but as far as I can tell the truck is not overheating and still runs great. I have checked all the normal causes, any suggestions?

 

Replace the sending unit.

Which engine?

 

Already replaced sending unit.
Engine is a 5.8 351

 

Did you use the correct sender? There are different senders for gauge or light.