Torque Converter Clutch (TCC) Check

TCC Diagnostic Chart:

Torque Converter Clutch Circuit:

Circuit Description:
The purpose of the Torque Converter Clutch (TCC) 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.

Switched battery voltage is supplied to the TCC solenoid which is located on the valve body. When the PCM/TCM closes the TCC driver, the solenoid will activate a valve within the valve body. Pressure will then be applied to the [1][2]torque converter clutch. The PCM/TCM will continue to open and close the TCC driver very rapidly to modulated pressure.

TCC will engage when:
^ Vehicle speed is above 30 mph (48 km/h).
^ Engine at normal operating temperature (above 65°C) (149°F).
^ Transmission at normal operating temperature 95°C (195°F).
^ Throttle position sensor output not changing, indicating a steady road speed.
^ Brake switch closed.
^ 4th gear.
^ No codes stored.

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.

1. The first portion of the test checks for a shorted, internal transmission harness or TCC solenoid.

2. The second part of the test verifies power supply to the TCC solenoid.

3. This step checks CKT 422 for a short to ground.

4. The final step checks the PCM/TCM ability to control the TCC solenoid.


Diagnostic Aids:
Be sure to check all connections especially those at the transmission pass-thru connector.

If they are OK, - Intermittent Malfunctions

The TCC solenoid is pulse width modulated and designed to keep the TCC right at the point of engagement. Therefore, some slight slip is normal.