So I have not updated my profile so I will lead with my pickup is a 2015 Duramax 3500 4wd (I believe its an LML not positive), I started getting the code P01F0 last spring and after driving with the code for a bit I reset the code with a code reader, apparently the weather had warmed up to never trip the code again all summer. Now that the cold is back so is the code. Everything I have read online states it should be a bad Thermostat, I replaced both thermostats drained and put new coolant in the truck and reset the code again. Again as soon as we got another cool night the code popped up again. After some digging online someone recommended changing the coolant temp sensor. I did this and reset the code and again this morning the code popped up again. I have not actually read the code yet but I'm sure its the same one as the temps are cold again. I do not know what to do next any suggestions would be greatly appreciated. Trying to avoid taking it to the Stealer or a shop, as I try to fix anything I can to save myself a little $. Thanks in advance again.