Torque Converter Clutch: Testing and Inspection

Chart C-8 - Transmission Converter Clutch (TCC):

Wiring Diagram For Chart C-8 - Transmission Converter Clutch:

CHART C-8 TRANSMISSION CONVERTER CLUTCH (TCC)


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 24 mph
- Engine at normal operating temperature (above 65~C).
- Throttle position sensor output not changing, indicating a steady road speed.
- Brake switch closed.


Test Description:

1. A test light on indicates battery voltage and continuity through the TCC solenoids is OK.

2. Checks for vehicle speed sensor signal to ECM. Voltage should vary from under 2 to over 8 volts.

3. Checks for 4th gear signal to ECM. This signal will not prevent TCC engagement, but could cause a change in the engage and disengage speed points.


4. Solenoids are turned "ON" or "OFF" by the ECM internal electronic switches called "drivers". Each driver is part of a group of four called "Quad-Drivers". Failure of one can damage any other driver within the set. Solenoid coil resistance must measure more than 20 ohms. Less resistance will cause early failure of the ECM "DRIVER". Using an ohmmeter, check the solenoid coil resistance of all ECM controlled solenoids and relays before installing a replacement ECM. Replace any solenoid or relay that measures less than 20 ohms resistance.