Torque Converter Clutch: Testing and Inspection

Fig. 121 - Wiring Diagram for Chart C-8A Torque Converter Clutch. VIN R:

CHART C-8A

TORQUE CONVERTER CLUTCH (TCC) CIRCUIT


Circuit Description:
The purpose of the automatic transaxle torque converter clutch is to eliminate the power loss of the torque converter when the vehicle is in a cruise condition. This allows the convenience of the automatic transaxle and the fuel economy of a manual transaxle.
Fused ignition voltage is supplied to the TCC solenoid through the brake switch and transaxle third gear apply switch. The ECM will engage TCC by grounding CKT 422 to energize the solenoid.
TCC will engage under the following conditions:
- Vehicle speed is above 30 mph (48 km/h).
- Engine at normal operating temperature (above 70°C, 156°F).
- Throttle position sensor output not changing, indicating a steady road speed.
- Transaxle third gear switch closed.
- Brake switch closed.

Fig. 120 Chart C-8A Torque Converter Clutch:

Test Description:
Numbers below refer to circled numbers on the diagnostic chart.
1. Light "OFF" confirms transaxle third gear apply switch is open.
2. At 30 mph (48 km/h), the transaxle third gear switch should close. Test light will turn "ON" and confirm ignition voltage in circuit and close brake switch in closed position.
3. Grounding the diagnostic terminal with the engine "OFF" should energize the TCC solenoid. This test checks the capability of the ECM to control the solenoid.

Diagnostic Aids:
An engine coolant thermostat that is stuck open or opens at too low a temperature may result in an inoperative TCC.