To detect high-temperature sticking abnormality, the resistance of water temperature sensor is stuck to the resistance value associated with high temperature.

When cooling water has a high temperature (curve L2) in starting an engine, no significant fluctuation is observed in an output from a water temperature sensor like high-temperature sticking abnormality (curve L3). Namely, no high-temperature sticking abnormality in the water temperature sensor is detected in high-temperature starting, where an engine suspension duration before starting the engine is measured. The engine suspension duration exceeding the given value determines low cooling water temperature in starting the engine. The output from the water temperature sensor is monitored, after starting the engine to detect a difference in water temperature between the maximum and the minimum water temperature. The water temperature difference lower than the given determination standard value determines the presence of the abnormality in the water temperature sensor to detect the high-temperature sticking abnormality.