Theory Of Operation

The purpose of the diagnostic is to detect malfunctions which lead to an unexpected transmission ratio (e.g. slipping clutches, hydraulic or mechanical defects, etc.). The monitoring is done by an out-of-range check by comparing the actual gear ratio (i.e. the ratio of input speed to output speed) to a minimum and maximum calibrated gear ratio threshold. The function monitors the gear ratio while driving in a fixed gear, during gear engagement and during shifting from one gear to another.