Abstract: A coolant temperature sensor abnormality determination device includes a determination unit configured to determine whether or not two coolant temperature sensors, which are configured to detect the temperature of the coolant, have an abnormality. The determination unit has a determination permission condition under which a reference temperature is set to an estimated temperature of a present time point and the estimated temperature is then changed from the reference temperature by a determination temperature. The determination unit is configured to determine, when the determination permission condition is satisfied, that the two coolant temperature sensors are functioning normally if a discrepancy between detection values of the two coolant temperature sensors is less than a normal temperature that is less than or equal to the determination temperature.

Abstract: A throttle valve abnormality determination device includes a permission/rejection determination unit configured to determine whether or not to permit a sticking determination of a throttle valve. The determination unit is configured to prohibit the sticking determination if a first temperature, which is a temperature in a passage through which intake air flows, is less than or equal to a freezing temperature at which the throttle valve may be frozen when an engine is started and, after prohibiting the sticking determination, permit the sticking determination if an integrated value of a heat amount conversion value based on a second temperature, which is a temperature in the passage, and an intake air amount exceeds a threshold value when the second temperature is greater than or equal to a de-freezing temperature at which a frozen portion of the throttle valve is de-frozen.

Abstract: This thermostat abnormality determining device includes a cooling water temperature sensor, an estimated temperature calculating unit and a determining unit. The cooling water temperature sensor detects the temperature of cooling water that cools an engine. The estimated temperature calculating unit calculates an estimated temperature, which is an estimated value of the temperature of the cooling water. The determining unit determines if the thermostat has become stuck open after warming-up of the engine is complete.

Abstract: A throttle valve abnormality determination device includes a permission/rejection determination unit configured to determine whether or not to permit a sticking determination of a throttle valve. The determination unit is configured to prohibit the sticking determination if a first temperature, which is a temperature in a passage through which intake air flows, is less than or equal to a freezing temperature at which the throttle valve may be frozen when an engine is started and, after prohibiting the sticking determination, permit the sticking determination if an integrated value of a heat amount conversion value based on a second temperature, which is a temperature in the passage, and an intake air amount exceeds a threshold value when the second temperature is greater than or equal to a de-freezing temperature at which a frozen portion of the throttle valve is de-frozen.

Abstract: A coolant temperature sensor abnormality determination device includes a determination unit configured to determine whether or not two coolant temperature sensors, which are configured to detect the temperature of the coolant, have an abnormality. The determination unit has a determination permission condition under which a reference temperature is set to an estimated temperature of a present time point and the estimated temperature is then changed from the reference temperature by a determination temperature. The determination unit is configured to determine, when the determination permission condition is satisfied, that the two coolant temperature sensors are functioning normally if a discrepancy between detection values of the two coolant temperature sensors is less than a normal temperature that is less than or equal to the determination temperature.

Abstract: This thermostat abnormality determining device includes a cooling water temperature sensor, an estimated temperature calculating unit and a determining unit. The cooling water temperature sensor detects the temperature of cooling water that cools an engine. The estimated temperature calculating unit calculates an estimated temperature, which is an estimated value of the temperature of the cooling water. The determining unit determines if the thermostat has become stuck open after warming-up of the engine is complete.