Diagnostic Aids

A scan tool only displays if transaxle mode switch is on or off. If information displayed is correct, solenoid "A" is off and transaxle is not in 2nd gear, refer to appropriate automatic transmission article for hydraulic or mechanical diagnosis.

Fig 1: Chart C-8B, 4T60 Transaxle Troubleshooting 1 Of 4 (3.4L PFI W Body)

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. TCC will engage on a warm engine under given road load in 2nd, 3rd and 4th gears. 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 number refers to test number on diagnostic chart.
  1. This test checks functional operation of TCC circuit.
  2. This test checks TCC control driver in ECM.
  3. This test determines if voltage is present at terminal "A". If there is no voltage, check 10 amp fuse.
  4. This test confirms ECM has ability to turn TCC on.

A scan tool only indicates when ECM has turned on the 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.

Fig 1: Chart C-8B, 4T60 Transaxle Troubleshooting 2 Of 4 (3.4L PFI W Body)

Courtesy of GENERAL MOTORS CORP.

1. If there are any codes present, those codes must be repaired first. Transaxle will default to 3rd gear if Codes 21, 22, 24, 53 and 55 are present.
2. This test checks 1st gear switch status.
3. This test verifies 1st gear switch status change.
4. This test checks 4th gear switch status.

Fig 2: Chart C-8B, 4T60 Transaxle Troubleshooting 3 Of 4 (3.4L PFI W Body)

Courtesy of GENERAL MOTORS CORP.

The 4T60 transaxle uses 2 solenoids to control shifting: Shift solenoid "A" and shift solenoid "B". ECM monitors TPS and vehicle speed versus engine speed to determine correct shift points.

Fig 3: Chart C-8B, 4T60 Transaxle Troubleshooting 4 Of 4 (3.4L PFI W Body)

Courtesy of GENERAL MOTORS CORP.