Chart C-8, Torque Converter Clutch - 2.5L & 2.8L LT. Trucks & Vans: Notes

Fig 1: Chart C-8, TCC Circuit Diagram 1991 (2.5L & 2.8L Lt. Trucks & Vans)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Chart C-8, TCC Circuit Diagram 1992 (2.5L & 2.8L Lt. Trucks & Vans)

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 convener 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
  NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. Check continuity through the brake switch and TCC solenoid.
  2. Check ability of ECM to energize the TCC solenoid. Grounding the diagnostic connector should energize the relay and cause the light to go out.
  3. This test by-passes the TCC solenoid and checks for an open or short in circuit No. 422