| 摘要 |
A transmission diagnostic control effective when there is an apparent loss of the transmission output speed signal for determining if failure is real, and if so, the cause of the failure. When an apparent loss of the output signal is observed, the transmission is successively upshifted through its various forward speed ratios while the transmission input speed is monitored to detect the occurrence of an upshift-related reduction thereof. If the shifting fails to produce a reduction in the transmission input speed by the time the transmission has been shifted to the highest available speed ratio, a total transmission failure is indicated. If the shifting produces a decrease in the transmission input speed, a total failure of the transmission is ruled out, and the diagnostic control determines if the failure is transmission or sensor related. If the output speed signal is still absent and the input speed is still high enough, after a shift-related reduction, to generate vehicle motion, a speed sensor related failure is indicated. If the output speed signal indicates normal vehicle movement, the diagnostic control is terminated and all forward ratios lower than the current ratio are indicated as failed. |
