US Patent 7402123 Automatic transmission control method and system having fail-safe function

In an automatic transmission control system and method, an electronic control unit is programmed to output a command to establish another gear stage different from the gear stage at the time of occurrence of fault-induced disengagement by combination of engagements of the friction elements other than the friction elements to be engaged at the time of occurrence of fault-induced disengagement, and simultaneously output a plurality of commands to establish a plurality of gear stages corresponding to combination of engagements of the friction elements to be engaged and disengaged, respectively, at the gear stage at the time of occurrence of fault-induced disengagement, when the gear stage at the time of occurrence of the fault-induced disengagement is a predetermined gear stage and the friction element undergoing the fault-induced disengagement is not determined.