Vehicular automatic transmission equipped with failure detecting apparatus

A vehicular automatic transmission, comprising:

• a plurality of engaging elements;
• a shift gear mechanism in which combinations of engagement and release of the respective engaging elements are selected by means of hydraulic control section so as to perform a multiple range of gear shift;
• a hydraulic switching device that is installed in the hydraulic control section to prevent the shift gear mechanism from being interlocked;
• and
• a failure detecting apparatus to detect an occurrence of failure of the hydraulic switching device, the failure detecting apparatus including:
• a gear range determinator to determine in which gear range the present gear range of the automatic transmission falls;
• a failure detection start determinator to determine a start of the failure detection of the hydraulic switching device according to a result of determination by the gear range determinator;
• a memory storing parts of the engaging elements which are selected as the combinations of engagement for the respective gear ranges and other parts than those for the respective gear ranges in a table form;
• a hydraulic switching device checking device to intentionally output an engagement command signal to command to engage to each of the other parts of engaging elements which are not to be engaged and which are read from the memory;
• and
• a hydraulic switching device abnormality state determinator to determine through the checking device whether the hydraulic switching device is in an abnormal state depending on whether the hydraulic is transmitted to a corresponding one of the other parts of engaging elements in response to the engagement command signal.