Dtc p0128

Yesterday while driving on the highway the MIL light came up. I didn't notice any drivability problems or issues and performance has not changed at all.

I connected my ELM to read the DTC codes and this code P0128 - Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature) came up!

What are the causes, diagnostics and fixes to rid my self of this code? Thanks in advance.

It's taking too long for the engine to warm up, the coolant thermostat is probably sticking open. The engine has a window of time to get warm, if not a code is thrown.

1) New thermostat ; Reset clear code

Thanks for the info... appreciate your help! As soon as it starts warming up again, I'll look into it.