Diagnostic Aids

A scan tool only indicates when ECM has turned on TCC driver and does not confirm TCC has engaged. To determine if TCC is functioning properly, test drive vehicle. Engine RPM should decrease when scan tool indicates TCC driver has turned on. An engine coolant thermostat stuck open or opens at too low a temperature may result in an inoperative TCC.

Fig 1: Chart C-8A, TCC Troubleshooting Chart - 1 of 2 (3.1L PFI A, J & L Bodies)

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