Received PO128 Code Ford - Coolant Thermostat Issue, What’s the Fix?

[Nicko]

Hey guys, my 2012 Ford Explorer is giving me the PO128 code. From what I understand, it’s related to the coolant thermostat, but the car’s not overheating or anything. I’ve noticed the temperature gauge doesn’t reach the middle sometimes. Should I replace the thermostat, or could it be a sensor issue? Appreciate any advice