Component Tests and General Diagnostics

Chart C-8 "Torque Converter Clutch (TCC):

Wiring Diagram - Torque Converter Clutch (TCC):

CHART C-8

TORQUE CONVERTER CLUTCH (TCC) 200-4R (ELECTRICAL DIAGNOSIS)



Circuit Description:

The purpose of the automatic transmission torque converter clutch feature is to eliminate the power loss of the torque converter stage when the vehicle is in a cruise condition. This allows the convenience of the automatic transmission and the fuel economy of a manual transmission. Fused battery ignition is supplied to the TCC solenoid through the brake switch. The ECM will engage TCC by grounding CKT 422 to energize the solenoid.
TCC will engage when:

Vehicle speed above 38 mph.

Engine at normal operating temperature (above 70 degrees C, 150 F).

Throttle position sensor output not changing, indicating a steady road speed.

Brake switch closed.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Confirms 12 volt supply as well as continuity of TCC circuit.

2. Grounding the diagnostic terminal, with engine "OFF," should energize the capability of the ECM to control the solenoid.

3. The test light should go "OFF" if the circuit is OK as grounding terminal "P" shorts out the test light. Therefore, the quad-driver inside the ECM is faulty and the ECM must be replaced.

4. If the test light goes "OFF," the quad-driver inside the ECM is faulty and the ECM must be replaced.

5. Solenoid coil resistance must measure more than 20 ohms. Less resistance will cause the fault protected quad-driver to open repeatedly.


Diagnostic Aids:

An engine coolant thermostat that is stuck open, or opens at too low a temperature, may result in an inoperative TCC. If TCC engages before "Scan" indicates TCC "ON," wiring may be grounded between TCC solenoid and sump overtemperature switch or switch may be faulty. If "Scan" indicates TCC "ON" and test light goes out but TCC never engages, problem is hydraulic.