Torque Converter: Description and Operation

Torque Converter Electronics
The torque converter contains a converter clutch mechanism. The converter clutch is an electronically controlled mechanism. It is engaged in fourth gear, and in third gear only when the overdrive control switch is in the OFF position, and also, in third gear over temp mode.

The torque converter is not a serviceable component. It should be replaced as an assembly when:
diagnosis indicates a malfunction has occurred, or when a major malfunction allows debris to enter the converter.