Abnormal state diagnosis method for oil temperature sensor of automatic transmission

An abnormal state diagnosis method for an oil temperature sensor of an automatic transmission, the abnormal state diagnosis method comprising:

• performing, in an engine control module configured to control an engine, a warm-up judgment comprising judging whether or not a sensor value from an engine side temperature sensor during an engine warm-up state indicates the engine warm-up state;
• performing, in the engine control module, a sensor normal operation judgment comprising:
• reading a result of the warm-up judgment in the engine control module when the engine is restarted after waiting for an engine cold state from a stopping of the engine after the engine warm-up state, and
• starting to judge whether or not the engine side temperature sensor, accounting for the result of the warm-up judgment, performs an engine side temperature detection operation in a normal state;
• performing, in an automatic transmission control unit configured to control the automatic transmission, a provisional judgment comprising:
• receiving the sensor value from the engine side temperature sensor in the automatic transmission control unit configured to control the automatic transmission, which is connected with the engine when the engine is restarted after waiting for the engine cold state from the stopping of the engine after the engine warm-up state, and
• judging whether or not an upper deviation width or a lower deviation width between the sensor value of the engine side temperature sensor and an oil temperature sensor value from the oil temperature sensor of the automatic transmission is equal to or smaller than a predetermined threshold value;
• and
• performing, a final judgment comprising determining a result of the provisional judgment in the automatic transmission control unit when the automatic transmission control unit receives a permission signal outputted from the engine control module based on a judgment that the engine side temperature sensor is operated in the normal state.