Thermostat Monitor
WARNING: This page is about a different car, the 2021 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.
The thermostat monitor is designed to verify correct thermostat operation. The thermostat monitor checks for a thermostat that is operating correctly by estimating engine coolant temperature based on calibrated parameters of engine fueling and ambient temperature. The thermostat monitor compares the actual engine coolant temperature to the expected calibrated engine coolant temperature. If the actual engine coolant temperature is not within the calibrated value of the expected temperature, a DTC sets and the MIL is illuminated. This monitor is executed once per drive cycle.