Torque Converter Clutch: Testing and Inspection

Chart C-8A:

Wiring Diagram For TCC:

CIRCUIT DESCRIPTION:

The purpose of the automatic transmission Torque Converter Clutch (TCC) feature is to eliminate the power loss of the torque converter when the vehicle is in a cruise mode. This allows the convenience of the automatic transmission and the fuel economy of a manual transmission. Fused ignition voltage is supplied to the TCC solenoid through the brake and third gear switches. The ECM will engage the TCC by grounding circuit 422 to energize the solenoid.

The TCC will engage when the following conditions exist:

1. Vehicle speed above is between 26 and 40 mph (42 and 64 km/h).
2. Engine at normal operating temperature (above 70°C, 156°F).
3. Throttle position sensor output not changing, indicating a constant road speed.
4. Transaxle third gear switch closed.
5. Brake switch closed.


TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. A light "OFF" confirms transaxle third gear apply switch is open, which is OK in this step.
2. At 48 km/h (30 mph), the third gear switch should close. The test light will turn "ON" and confirm ignition voltage in the circuit, and close the brake switch.
3. Grounding the diagnostic terminal with the engine "OFF" should energize the TCC solenoid. This checks the capability of the ECM to control the solenoid.


DIAGNOSTIC AIDS:

An engine coolant thermostat which is stuck open or opens at a low temperature may result in an inoperative TCC. If electrical checks show that the circuit appears to be operating normal and a complaint still exists, check the TCC wiring inside the transmission, TCC solenoid, or check for an internal hydraulic problem.