2007 Ford Fusion Plate Light Keeps On Off Hit Bumps Shut Trunk Would Cause This

my plate light keeps going on and off when i hit bumps or shut my trunk what would cause this and my check engine light is on and the code tells me coolant temp lower than it should be i replaced the thermostat sensor light never went out so i erased the code to see if that would help but it came back on a day later so reading the same code is there another one i need to replace or is the sensor i bought just junk from get go just ben trying to figure this out and no one has an idea and nearest ford dealer is like an hour from me any advice would be nice thanks