Malfunction determination 1

If the difference between the current measured engine coolant temperature at the radiator (ECT 2) and the initial engine coolant temperature at the radiator (ECT 2) is at least 18 °F (10 °C) when the estimated engine coolant temperature at the engine (ECT 1) reaches 67 °F (20 °C), a malfunction is detected (thermostat stuck open); or if the engine coolant temperature at the radiator (ECT 2) only reaches 160 °F (72 °C), a malfunction is detected (thermostat malfunction).