Chart C-8A, Torque Converter Clutch Electrical Diagnosis - 1991 E Body (Except ELDORADO) 3.8L PFI (VIN L): Notes

Fig 1: Chart C-8A, TCC Circuit Diagram (1991 E Body (Except Eldorado) 3.8L PFI VIN L)

Courtesy of GENERAL MOTORS CORP.

When solenoid coil is activated, TCC is applied which results in a straight through mechanical coupling from engine to wheels. When solenoid coil is deactivated, TCC is released which allows torque converter to operate in conventional manner. PWN solenoid varies hydraulic pressure to make locking and unlocking of TCC smoother. TCC will engage under the following conditions:

• Engine is warmed up.
• Vehicle speed above a calibrated value of about 28 MPH.
• Throttle position not changing, indicating a steady speed.
• Brake switch is closed.
  NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. This test checks fuse, brake switch and B+ circuit to TCC solenoid.
  2. This test checks availability of voltage on circuit No. 420.
  3. This test checks PCM's capability to pulse PWM solenoid on and off.
  4. Electrical circuits have checked out okay. See appropriate AUTO TRANS OVERHAUL article for hydraulic and mechanical diagnosis.