GM Failsafe Limp Mode on 2015 GMC 1500 3.6L

About two weeks ago my dad’s truck went into limp mode while on the way to the store. Everything pointed to thermostat sensor or thermostat. Fans kicked on with no boiling. We cleaned the sensor and the truck was back to normal. About two days afterwards the problem happened again so we changed the sensor. Come present day the problem has popped back up after running perfectly fine for weeks. When my dad turned on his truck this morning the fans instantly kicked on. His coolant levels are good and wiring seems to be good at least on the top part of the engine I haven’t gone under yet. We did have flooded roads a while ago that he had to drive through to make it back home. So i’m thinking maybe the corrosion and buildup is finally taking place? Any advice or information would be insanely helpful as this has me stumped.