My engine runs stone cold all the time, I unplug the motor at the radiator to warm engine enough to make check engine light go out long enough to re-register. I've replaced the thermostat
and temp sensor twice, replaced the relays in the under the hood fuse box. Sometimes when it's humid or raining the a/c snowflake light comes on and nothing I do shuts it off. In the summer it's very hot where I live but all winter I have the check engine light and code telling me I need a stat or sensor. Could it be in the controls in the dash? Sticking or making contact when it's moist enough.