Diagnostic Aids

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

If ECM TCC solenoid and control circuitry are functioning correctly but TCC still does not apply properly, problem may be hydraulic or mechanical. See appropriate AUTO TRANS OVERHAUL article.

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

Courtesy of GENERAL MOTORS CORP.