Abnormality determination apparatus and abnormality determination method for coolant temperature sensor, and engine cooling system

摘要

When a temperature difference between intake air temperature that detected by an intake air temperature sensor and engine coolant temperature thw1 detected by an engine coolant temperature sensor is greater than a threshold value, a coolant temperature sensor abnormality determination apparatus opens a changeover valve to cause the coolant to flow into an engine coolant passageway, thereby mixing the coolant in an engine and the coolant in a heater passageway (bypass passageway). If the temperature difference between the engine coolant temperature thw1 and a heater inlet coolant temperature (bypass coolant temperature) thw2 occurring after the changeover valve opens is less than or equal to a predetermined value, the apparatus determines that the engine coolant temperature sensor is normal. If the temperature difference is greater than the predetermined value, the apparatus determines that the engine coolant temperature sensor is abnormal.