Torque Converter Clutch Solenoid: Description and Operation

Torque Converter Clutch Solenoid:

The purpose of the Transmission Converter Clutch (TCC) feature is to eliminate the power loss of the torque converter stage when the vehicle is in a cruise mode. The TCC system uses a solenoid operated valve to couple the engine flywheel to the output shaft of the transmission through the torque converter. This reduces the slippage losses in the converter, which increases fuel economy. For the converter clutch to apply, at least two conditions must be met.

^ Internal transmission fluid pressure must be correct.
^ The ECM completes a ground circuit to energize the TCC solenoid in the transmission, which moves a check ball in the fluid line and allows the converter clutch to apply..

The ECM controls the TCC apply solenoid by looking at several sensors.

^ Engine must be in closed loop operation.
^ Vehicle Speed Sensor (VSS). Speed must be above a certain value before the clutch can apply.
^ Coolant Temperature Sensor (CTS). Engine must be warmed up before the clutch can apply.
^ The 3T40 transmission uses 2nd, 3rd gear switches which are direct inputs to the ECM. The ECM uses the switch signals for TCC engage and disengage points.
^ Throttle Position Sensor (TPS). After the converter clutch applies, the ECM uses the information from the TPS to release the clutch when the car is accelerating or decelerating at a certain rate.
^ Another switch used in the TCC circuit is a brake switch which opens the 12 volt supply to the TCC solenoid when the braske is depressed.