Abstract: A method and apparatus for diagnosing a failure of an output shaft speed sensor of an automatic transmission is provided, which comprises: determining whether a current transmission is a forward driving range; determining whether a failure criterion exists based on a current gear, an input shaft speed, an output shaft speed, and an engine speed, if the current transmission is the forward driving range; and maintaining the current gear if a downshift criterion exists, or upshifting a gear if a upshift criterion exists, if the failure criterion exists.

Abstract: A method for controlling a damper clutch of an automatic transmission that can perform a normal shifting quality by selecting a correction value according to an outside air temperature for direct connection of the damper clutch and delaying the direct connection of the damper clutch until the operational oil temperature rises by considering the correction value to thereby enable it to get to an appropriate degree of operational oil temperature, a normal state of operational oil, the method for controlling a damper clutch of an auto transmission comprising the steps of: detecting the outside air temperature; correcting oil temperature to determine a point of time for direct connection of the damper clutch according to the determined outside air temperature; and performing controlling operations for direct connection of the damper clutch with a requirement that the operational oil temperature reaches to the correction value.

Abstract: A fault diagnosis method is provided in which it is possible to determine whether the input shaft speed sensor of the automatic transmission is faulty by using the signals of the output shaft speed sensor, the brake switch, the engine speed sensor and so on, without making use of the signal of the vehicle speed sensor. Moreover, even if there are faults in the output shaft speed sensor or if the shift lever is positioned in the parking P range or the neutral N range, or if the engine speed is lower than the stall speed, the fault diagnosis method for the input shaft speed sensor can be performed, and additionally, a possibility of a misjudgment caused by a bad N-D hydraulic pressure response at an extremely low temperature can be removed.