SENSOR DIAGNOSTIC DEVICE

A sensor diagnostic device for use in a vehicle including a first temperature sensor and a second temperature sensor includes a control system. The control system includes a processor and a memory communicably coupled to each other. The control system determines a sensor abnormality based on a detected temperature difference between a first detected temperature detected by the first temperature sensor and a second detected temperature detected by the second temperature sensor. After the vehicle is stopped, the control system calculates a decrease speed of the first detected temperature based on the first detected temperature, and calculate a decrease speed of the second detected temperature based on the second detected temperature, and if an absolute value of a decrease speed difference between the first and second detected temperatures is smaller than a threshold, determines whether the sensor abnormality has occurred, based on the detected temperature difference.