Failure determination system for stepless speed changer and failure determination device for start clutch

摘要

There is provided a failure determination system for a continuously variable transmission of a belt type, which is capable of determining failure of control valves for performing speed varying operation, and enhancing maintainability. An ECU controls a transmission ratio of the transmission to a fixation-determining LOW-side range when the vehicle is standing. When the transmission ratio during stoppage of the vehicle is within a stop-time OD-side range if engine torque≧OD-time DR-side reference torque and at the same time the transmission ratioDN-side reference value hold, the ECU determines that the DR solenoid valve is faulty, and if the throttle valve opening≧OD-side reference value, the transmission ratio≧DN-side reference value, and at the same time a vehicle speedOD-side reference value hold, the ECU determines that the DN solenoid valve is faulty.