Torque Converter Diagnosis

Torque Converter Diagnosis





Prior to torque converter replacement, all diagnostic procedures must be followed. This is to prevent the unnecessary installation of new or remanufactured torque converters. Only after a complete diagnostic evaluation can the decision be made to install new or remanufactured torque converters.

NOTE: If equipped, turn the Power Take-Off (PTO) unit off for correct test results. For a description of PTO operation, refer to Transmission Electronic Control System Transmission Electronic Control System.

During PTO operation, the On-Board Diagnostic (OBD) will be disabled. However, the circuit checks made by the diagnostic system and the Failure Mode Effect Management will continue. The PTO must be turned off to do OBD test.

Begin with the normal diagnostic procedures as follows:

1. Preliminary Inspection.

2. Know and Understand the Customer Concern.

3. Verify the Concern - Carry out the Torque Converter Operation Test.

4. Carry out Diagnostic Procedures. Diagnostics
- Run OBD test. Refer to On-Board Diagnostics with Scan Tool. Diagnostics
- Repair all non-transmission-related DTCs first.

- Repair all transmission DTCs.

- Rerun the OBD test to verify repair.

- Carry out Line Pressure Test. Line Pressure Test

- Carry out Stall Speed Test. Stall Speed Test

- Carry out Diagnostic Routines. Diagnostic Routines
- Use the Diagnosis by Symptom Index to locate the appropriate routine that best describes the symptom(s). The routine will list all possible components that may cause or contribute to the symptom. Check each component listed. Diagnose and repair as required, before repairing the torque converter.


Torque Converter Operation Test

This test verifies that the Torque Converter Clutch (TCC) control system and the torque converter are operating correctly.

1. Carry out Self Test, refer to On-Board Diagnostic (OBD) with Scan Tool. Check for DTCs. Refer to Diagnostics Diagnostics.

2. Connect a scan tool and monitor engine parameters.

3. Bring the engine to normal operating temperature by driving the vehicle at highway speeds in the (D) position.

4. After normal operating temperature is reached, maintain a constant vehicle speed of about 80 km/h (50 mph) and tap the brake pedal with the left foot.

5. Engine rpm should increase when brake pedal is tapped and decrease about 5 seconds after pedal is released. If this does not occur, refer to Diagnosis By Symptom Diagnosis By Symptom - Torque Converter Clutch Operation Concerns.