My check engine light came on and took it to Advance Auto to scan for codes. I received a P0128 code that says "coolant temp below thermostat regulating temp". Is this the thermostat or a sensor? Car is not running strange or hot everything is normal acting so far.

 

Needs a thermostate . It stuck open causing engine not to warm up. Causing that code

 

Jag_genius so just put in new thermostat and clear code? No need for the dealership? Thanks for you help.

 

just put an ew 1 in and clear, Im assuming you have the new multi piece t stat cause the old ones never kicked that code. They just overheated the engine sticking closed. Youll find when you pull it out that the rubber seal around the edge of the thermostat itself has a small tear or piece missing letting coolant bypass causing the threashold to not be met, Ide rather have a t stat stick open over closed any day