Mr. Detail--AJU could be right after my lengthy post on being careful removing the thermostat housing to get to the temp sensor. Most temp sensors do not bottom out suddenly, but become erratic. It never hurts to take the thermostat housing loose to keep the two torx bolts from seizing. Reinstall with anti-lock. You will see though white corrosion around the leads of the temp sensor, but they go inside a housing that is sealed and you can't tell if the corrosion has followed the leads inside or not. Dick