Diagnostic apparatus and diagnostic method for belt squeezing force adjusting mechanism

摘要

A condition that a target speed ratio RATIOT be in a region less than a predetermined speed ratio c is a precondition for performing a diagnostic on a belt squeezing force adjusting mechanism (specifically, a solenoid valve) of a continuously variable transmission (S102). This region where RATIOT < c is a region that is outside of a region that can be reached when there is a malfunction in the solenoid valve. When RATIOT ‰¥ c (NO in S102), a diagnostic will not be performed on the belt squeezing force adjusting mechanism so that an erroneous diagnosis that the belt squeezing force adjusting mechanism is functioning normally even though it is not will not be made. If the actual speed ratio is not able to come close to the target speed ratio RATIOT (DWDLPR < e) when RATIOT < c and control is being performed to reduce the speed ratio (PDS1 ‰¥ 1) (YES in S104), a malfunction determination is made (S106). Also, if the actual speed ratio is able to come close to the target speed ratio RATIOT in the region where RATIOT < c (DWDLPR ‰¥ f, NO in S104, YES in S108), a normal determination is made (S110). In this way, an erroneous diagnosis can be prevented so the diagnostic can be performed accurately on the belt squeezing force adjusting mechanism.