Chart C-8, Torque Converter Clutch - 4.3L, 5.0L, 5.7L: Notes

Fig 1: Chart C-8 - TCC Circuit Schematic (4.3L, 5.0L & 5.7L)

Courtesy of GENERAL MOTORS CORP.

The purpose of TCC is to eliminate the power loss of torque converter stage when vehicle is in "cruise" condition. This allows the use of an automatic transmission with the fuel economy of a manual transmission. Fused battery ignition power is supplied to TCC solenoid through the TCC brake switch. The ECM will engage TCC by grounding circuit No. 422 to energize the TCC solenoid. Engagement of torque converter clutch will be executed under the following conditions:

• Vehicle speed greater than 24 MPH.
• Engine temperature above 149°F (65°C).
• Steady TPS reading (not changing-steady road speed).
• Brake switch closed.
• Transmission in 3rd or 4th gear.

1. Glowing test light indicates that battery voltage and continuity through TCC solenoid are okay.
2. Checks for vehicle speed sensor (VSS) signal to ECM, using a SCAN tester.
3. Checks for 4th gear signal to ECM. This signal will not prevent TCC engagement, but could cause a change in engage/disengage speed points.