Torque Converter Clutch: Description and Operation

TCC Solenoid:

TORQUE CONVERTER CLUTCH SYSTEM

CIRCUIT DESCRIPTION
The 12 volt power supply for the solenoid in the transmission is provided through a normally closed switch located on the brake pedal linkage. When the brake pedal is depressed (switch open) the power supply to the Torque Converter Clutch (TCC) solenoid is interrupted and the TCC is disengaged regardless of any other conditions.

When the brake pedal is not depressed (switch closed), battery voltage will be fed to the TCC solenoid. If the ECM has determined that conditions are correct and the fluid pressure is below 415 kPa (60 psi), the circuit from the TCC solenoid will be completed to ground through the ECM and the TCC solenoid will be activated.

PURPOSE
The TCC system is designed to eliminate power loss by the converter (slippage) to increase fuel economy. By locking the converter clutch, a more effective coupling to the flywheel is achieved. The converter clutch is operated by an Engine Control Module (ECM) controlled solenoid.

OPERATION
Engagement of the TCC is accomplished by a solenoid operated valve within the transmission. The solenoid is activated when an internal switch in the ECM is grounded. Although the ECM may command the TCC "ON," the converter clutch will not apply until internal transmission fluid pressure requirements are met. Fluid pressure must be below 415 kPa (60 psi).

Before the ECM activates the TCC solenoid, several inputs must be monitored:

^ Vehicle Speed - Must be above a certain value before the TCC can be applied.
^ Engine Coolant Temperature - The Engine Coolant Temperature (ECT) must be above a certain value before the TCC can be applied.
^ Throttle Position (TP) Sensor - After the TCC is applied, during low engine load condition, the ECM uses the information from the TP sensor to release the clutch when the vehicle is accelerating or decelerating at a certain rate.