Why is my ETC light coming on?

What is your question?

I have a 2011 Dodge Nitro. Over the last two months my ETC light will periodically come on. No engine lag, sputtering or anything like that. Each time I start the car from being off it isn't on. Then I'll drive for a bit and the engine will heat up to between the quarter and halfway mark on the temp gauge then the temp gauge will slowly drop down all the way to cold. As soon as the temp gauge comes all the way down the ETC light will come on. Again no stuttering or stalling from the engine, just the light. The check engine light comes on but the only code that it's throwing is for low coolant/ thermostat reading error. I've checked and the coolant level is good, and I just changed the thermostat 7-8 months ago. Any help will be appreciated.

What makes this problem better or worse?

Light only comes on after the temp gauge raises and then lowers back to cold

How long has your 2011 Dodge Nitro had this problem?

A couple months