Output shaft speed sensor failure diagnosing method for vehicles, involves determining whether failure criterion exist based on current gear, and maintaining current gear if downshifts criterion exists

摘要

The method involves determining whether transmission is in a forward gear, and whether a failure criterion exists based on a current gear, an input shaft speed, an output shaft speed, or an engine speed, if the transmissions in a forward gear. The current gear is maintained if a downshifts criterion exists, or the gear is up-shifted if an up-shift criteria exists, if their exist a failure criterion. An Independent claim is also included for a system for diagnosing a failure of an output shaft speed sensor of an automatic transmission.