movement of a shift lever to various positions corresponding to the different shift ranges and outputs corresponding signals the throttle valve position sensor 200 detects throttle valve opening which varies according to driver manipulation of an accelerator pedal and outputs corresponding signals the atf temperature sensor 300 detects a temperature of automatic transmission fluid and outputs corresponding signals the turbine rpm sensor 400 detects rpm of a turbine of a torque converter and outputs corresponding signals and the transmission output sensor 500 detects output rpm of a transmission and outputs corresponding signals the transmission receiving an output of the torque converter through the turbine and varying this rotational force before outputting the same after receiving the signals from the inhibitor switch 100 the throttle valve position sensor 200 the atf temperature sensor 300 the turbine rpm sensor 400 and the transmission output sensor 500 the ecu 600 determines a present shift range of the vehicle and also whether roll over of the one way clutch has occurred if the one way clutch has undergone roll over the ecu controls the lrb driver 700 so that shifting into the second speed is realized fig2 shows a flow chart of a fail safe control method for an automatic transmission having a one way clutch according to a preferred embodiment of the present invention if the driver controls the shift lever into a drive d range in step s 100 the inhibitor switch 100 detects this re positioning of the shift lever and outputs a corresponding signal to the ecu 600 and the atf temperature sensor 300 outputs the change in atf temperature to the ecu 600 in step s 200 using these signals the ecu 600 determines that the shift lever has been positioned in the drive d range in particular.