My 2020 Supercrew is back in the shop again. Literally a few days after getting it back from them replacing the wiring harness with the knock sensors and coolant sensor I noticed the engine was running cold and taking forever to warm up. Sometimes you will be sitting at a traffic light and the temperature gauge will just start dropping back down to the cold. And then to make things even more complex, there are days it is fine and runs between 190-200 degrees. Last Friday I drove the whole way home with no heat. The engine just would not get warm. Then the next day I ran some errands and it ran fine with temps between 190-200 degrees all day. Any help here would be appreciated because the dealership is perplexed why it's doing this. I have 3 hours of video on my phone of me driving with the temperature gauge barely moving off the cold. The shutters are working as they are supposed too. I even went as far as using the infrared temperature gun to check engine temperatures on days the temperature gauge was reading on the cold side to see if the engine was actually running cold and it was. After a half hour of driving I got a reading of 130 degrees off the front of the cylinder heads. The issue is, without the truck kicking a fault code they really can't do much. Also for those who don't know, the cooling system runs on a series of valves that open and close to control engine temperature. It's a very complex and overengineered system and the service manager said it could take days to figure out why somedays the truck runs cold and other days it runs hot. Anybody who has experienced this before or who might be able to help us out please feel free to comment.