Theory Of Operation
WARNING: This page is about a different car, the 2016 Dodge Durango. However, it is still accessible from the selected car via links, so may be relevant.
The Transmission Control Module (TCM) monitors for conditions which lead to an unexpected transmission gear ratio (e.g. slipping clutches, hydraulic or mechanical defects, etc.). The TCM compares the actual gear ratio (i.e. the ratio of input speed to output speed) to a minimum and maximum calibrated gear ratio value. The TCM performs this comparison while driving in a fix gear, during gear engagement, and during shifting from one gear to another.