DIAGNOSTIC SYSTEM FOR AUTOMATIC TRANSMISSION

摘要

A diagnostic system for an automatic transmission is provided in which a microcomputer determines that torque that can drive the driving wheels of the vehicle is not transmitted to an output shaft of the automatic transmission when the vehicle is stopped and the ignition key is operated to the OFF position (steps S1OO, S11O), and performs forced energization of solenoids of solenoid valves associated with respective friction devices of the transmission (step S120), while monitoring current passing through the solenoid valves (step S130). If the current monitored does not match the current for energizing any of the solenoids, the microcomputer determines that the corresponding solenoid valve is at fault. Thus, the diagnostic system appropriately determines the presence of a fault of each solenoid valve for controlling the hydraulic pressure to each friction device, with increased flexibility and freedom.