Chart C8A - TCC: Notes

The purpose of the Torque Converter Clutch (TCC) feature is to eliminate the power loss of the transmission 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. Electrical power from the ignition circuit is supplied to the TCC solenoid through the brake switch and transmission 3rd gear switch. The ECM will engage TCC by grounding circuit No. 422 to energize the solenoid.

1. If test light is off, this confirms 3rd gear switch is open.
2. At 25 MPH, the 3rd gear switch should close. Test light will come on and confirm battery supply and closed brake switch.
3. Grounding the diagnostic "test" terminal with ignition on and engine off should energize the TCC solenoid when ECM grounds circuit No. 422. This test checks the ability of the ECM to supply a ground to the TCC solenoid. The test light connected from 12 volts to ALDL terminal "F" will turn on as circuit No. 422 is grounded.