Engine coolant gauge

Perhaps the thermostat is stuck open.

I have a 2012 Cruze, with the same issues.. I had a "ac off due to high engine temp" flash on the dash and it stopped reading the engine temp all together. I reset it with a obd reader and it started working again. I've recently changed the coolant temp sensor and thermostat 2x . It use to run 210* now it won't get over 179* doesn't blow the same heat it use to. I GAVE UP .. put cardboard in the radiator, Just make sure you don't block off the condensers!!

Change the thermostat and the coolant temp sensors...$ 200.00

i guess I was lucky. Had the same warning, changed the sensor near the thermostat and problem solved. I did lose the stupid retainer clip though, and had to get another. Hint...make sure the washer from the old sensor is out or the clip won't line up and click on.. Took me a long frustrating time to figure that out.