Torque Converter Clutch Solenoid: Description and Operation

Torque Converter Clutch Solenoid:

PURPOSE
The Transmission Converter Clutch (TCC) feature eliminates the power loss of the torque converter stage when the vehicle is in a cruise mode.

OPERATION
The TCC system uses a solenoid operated valve in the automatic transmission to couple the engine flexplate 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, two hydraulic 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.

ECM control is based on the input of three sensors:
- Vehicle Speed Sensor (VSS): Vehicle equipped with A/C will allow TCC engagement at about 35 mph when the A/C is selected "ON". Engagement will occur at a vehicle speed of about 30 mph (25 mph for 92) when A/C is selected "OFF".
- Engine Coolant Temperature (ECT) Sensor: Engine at normal operating temperature (above 65°C/149°F).
- Throttle Position Sensor (TPS): Output not changing, indicating a steady road speed.

ECM is also controlled by these switches:
- Brake switch closed: 12 volts supplied when brake is depressed.
- 3rd gear switch applied.