My temperature guage keeps going to 0 and the engine fans come on. I have checked and I have 5 volts to the sensor and I have checked the ohms resistance of the sensor and it is good. What else can I check?

This problem started after I put a overflo tank on the car it had a bolt in the hose with a clamp on it. After the guage drops it sets the code and once I erase the code the guage pops back up. Mabe I have a air pocket I cant get rid of.

Maybe some one will post an answer to your problem. I have a 2001 malibu that does the same thing. It will actually fix itself for a while then it will quit working again, seems to be worse when its cold weather. It has been doing it for over two years. I could live with it but it really makes my MPG suck and runs both cooling fans continuosly. Good luck.

It was the thermostat. I was told that when the pcm does not recieve the right temp signal it defaults the guage to zero and turns the engine fans on and that is why you are getting the bad mileage is because the pcm controls all of the engine adjustments do to what it thinks the engine temp is.