Position Sensor
The TCM uses the position of this switch housed on the TCM and main control valve body, to determine the selected gear range on the Automatic side of the selector lever.
The selector lever is connected to the transmission by a cable, which operates the transmission selector shaft between positions Park, Reverse, Neutral and Drive. The TCM detects the drivers choice of manual range selection (5,4,3,2) by means of a 3-bit code generated by the J-gate. This 3-bit code is then transformed in to a CAN message by the J-Gate module and transmitted on to the CAN bus where it is detected by the TCM.
The TCM uses this information to generate the CAN message "Gear Position Selected", which must not be confused with the similar message "Gear Position Actual" indicating the current mechanical gear ratio activated by the TCM.
Movement of the lever between Park, Reverse, Neutral and Drive manually controls the flow of transmission fluid, the TCM having control of the forward gear selected in Drive. Additional movement of the lever to 5,4,3 and 2 positions does not manually modify the fluid flow, the TCM detects these positions, and controls the gear selected electronically.