Torque Converter Clutch Solenoid: Description and Operation

Part Throttle Unlock Solenoid (3 Speed Automatic):

This solenoid is controlled by the engine controller. The engine controller applies and removes the ground from this solenoid to engage or disengage the lock-up torque converter. The lock-up torque converter is only locked up when the transmission is in direct drive and when the throttle position is not fluctuating. If the engine controller receives a signal from the throttle position sensor that an increase or decrease in throttle is needed (when the transmission gear selector is in direct drive), the engine controller will disengage the part throttle solenoid causing the lock-up torque converter to be disengaged.