US Patent 11174777 Abnormality detection system of engine cooling water recirculation system

To estimate an engine cooling water temperature, four learned neural networks (150A, 150B, 150C, and 150D) are stored, in which weights are learned for the four states of whether the grille shutter (50) is opened and whether air blown by the blower (63) circulates through the air-conditioning use heater (65). The engine cooling water temperature is estimated using any one of the learned neural networks selected from among the four learned neural networks (150A, 150B, 150C, and 150D). An abnormality of the engine cooling water recirculation system is detected based on the estimated value of the engine cooling water temperature.