I've done a lot of research on this forum regarding the usual temp guage having no reading, fans stay on after car is off, CEL; which are all issues that I am having. A week ago I replaced the temp sensor and things seemed fine. The temp guage would read about at the halfway mark. Other times the guage would read at the quarter mark, which I think is low. SO I should replace the t-stat for starters since the sensor is new. I'm kickin' myself for not doing both at the same time!! The CEL code was P0420 which the temp guage is listed as a possible culprit along with O2 sensor, cat and some others. Would a stuck t-stat trip this code? The temp guage can't get a good reading on the coolant and throws the code? Should I also replace the wire connectors to the temp sensor? They looked ok. Would P0420 show because the engine is warm but because the temp guage isn't reading it runs the car rich? I did clear the code and then about an hour later the guage quitall together.
Thanks and I'm sure this is kind of beating a dead horse but I would besurprised ifa bad t-stat would cause the temp sensor to quit.I hope I'm wrong.

 

sounds like a tstat to me

 

Thanks Kweef for the reply. I think that youwere right. I changed out the t-stat and replaced the wire connection to the temp sensor and so far the car is running warmer and the guage is always working. So far no CEL either. Thanks to this forum for all the knowledge that I gained from having this issue. I'm still surprised a t-stat could cause so much hate and discontent.

 

Update! CEL light came back on for P0420 again. I changed the Cat out and she has been running great now for about 2 weeks. The old cat was an aftermarket universal fit oneand it probably didn't react too well to the car always running cool.I'm glad I've got connections to parts at cost!

 

Glad to hear you`re running again.
Did you clean out the sensor in the U-bend while replacing the cat? If your cat went bad, I would probably clean out that sensor as well. If you still have the actual sensor connected, that is.