95 Grand Prix GTP cooling issue

I have a 3.4l engine in my 95 Grand Prix that I have replaced the head gaskets (and all gaskets above) on my car with the help of my friend, and have two symptoms with cooling. I also replaced the coolant sensor during re-assembly. My dash light <check engine> is always on, and the radiator fans come on immediately even after sitting outside in 30 degree temps all night. Also, my temp gauge for the coolant indicates its its almost red line hot (it has a new 180 degree thermostat in)--and i've bled both coolant bleeders of air. I don't think I have a plugged/clogged coolant system, as I also flushed it before putting it back together. Ok what am I missing? Your help is greatly appreciated and Happy Turkey Day :)

Welcome to AF!!

When you installed the sensor did you use teflon tape? If so remove the sensor and replace the tape with a conductive sealant and the problem should go away. You may also want to put a new sensor on when you replace the tape just to be on the safe side since, if the sensor is bad, then you won't have to replace it twice. Obviously the sensor is sending incorrect temps to the PCM causing the fans to come on when not needed.

I'm sure we used something other than teflon tape, but I'm sure its same problems/different sealant. It amazes me that something so minor could be at fault--. I really appreaciate your wisdom!!!!!!!!!!!! Thanks again and i'll try your suggestion.