Diagnostic Aids

A scan tool only indicates when ECM has turned on the TCC driver and does not confirm TCC has engaged. To determine if TCC if functioning properly, test drive vehicle. Engine RPM should decrease when Scan tool indicates TCC driver has turned on.

If ECM, TCC solenoid and control circuitry are functioning correctly and TCC still does not apply properly, problem may be hydraulic or mechanical.

Fig 1: Chart C-8A, 3T40 Troubleshooting Chart (3.3L PFI N Body)

Courtesy of GENERAL MOTORS CORP.