P0128 DTC code

Anyone have any experience with this code on a Fusion? It's telling me the car isn't heating up fast enough and pointing to a thermostat problem. It has since reset and not returned but when or hopefully IF it returns I'd like to be "in the know" so to speak.

at some point the t-stat stuck open. I have replaced a couple for this.

The coolant sensor is telling the ECU, it's too cool for a period time while the engine is warming up!
It could be a bad sensor or a stuck thermostat.

Check coolant level when cold, and make sure the fan is'nt on, thus cooling the coolant system during warm up period.

If the Air cond is on during warm up period, the air condenser fan could be keeping the coolant colder in the system for a longer period of time.

Thanks for the info. The CE light has been off almost two months so still hoping this was a one off glitch.

Light finally stayed on long enough to let the dealer see it. They changed the T-stat. Fell under the emissions warranty so didn't pay a dime.

Have also had this code. Borrowed scan tool and went for a drive, both coolant temp senders tracked together and varied from 172F to 178F. Outside air temp was 79F. Have slightly over 100k on my 2007 4cyl. Assume this is outside of normal emissions warranty? Think California residents get a 150K mile warranty. Thermostat is buried under power steering pump. Is pump removal required? Thanks for any tips.