Diagnostic Aids

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

Fig 1: Chart C-8A, TCC Troubleshooting Chart 1 Of 2 (3.8L PFI VIN L) W Body)

Courtesy of GENERAL MOTORS CORP.

Each gear switch opens when appropriate clutch is applied. All gear switches are open in 4th gear.

1. Scan tool should display NO for 2nd, 3rd and 4th gear, indicating all switches are closed.
2. This test determines whether switch of signal circuit is open. circuit can be checked for an open by measuring voltage with a DVOM at TCC connector. Voltage should be about 12 volts.
3. Because switch should be grounded in this step, disconnecting TCC connector should cause displayed switch states to change.
4. Switch state should change when vehicle shifts into 3rd gear.

If vehicle is road tested because of a TCC related problem, ensure switch states do not change while in 4th gear. TCC will engage. If switches change state, carefully check wire routing and connections. If ECM, TCC solenoid and control circuitry are functioning correctly and 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 2 Of 2 (3.8L PFI VIN L - W Body)

Courtesy of GENERAL MOTORS CORP.