Torque Converter Diagnosis

Torque Converter Diagnosis





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

Begin with the normal diagnostic procedures as follows:

1. Preliminary inspection.

2. Know and understand the customer concern.

3. Verify the condition - carry out the Torque Converter Operation Test.

4. Perform diagnostic procedures.

- Perform On-Board Diagnostic (OBD) test. Refer to Diagnostics Diagnostics. Visual Inspection
- Repair all non-transmission related DTCs first.
- Repair all transmission-related DTCs.
- Rerun OBD test to verify repair.

- Perform Stall Speed Test. Refer to Special Testing Procedures Special Testing Procedures.
- Perform Diagnostic Routines. Refer to Diagnosis By Symptom Diagnosis By Symptom. Diagnostic Routines
- Use the Diagnosis by Symptom 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 changing the torque converter.


Torque Converter Operation Test

The Torque Converter Operation Test verifies that the Torque Converter Clutch (TCC) control system and the torque converter are operating correctly.

1. Perform a Self Test with the scan tool. Refer to Computers and Control Systems Information. Check for DTCs.

2. Connect a scan tool to the vehicle.

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 speed of about 56 km/h (35 mph) in 5th gear for 10 seconds.

5. Release the accelerator pedal and monitor the scan tool Throttle Position (TP) voltage to approximately 1.25 volts or 25% throttle.

6. Monitor the TCC and RPM TCM PID. The TCC should release and engine rpms should increase before the 5-4 shift occurs.

NOTE: The following is a list of common vehicle concerns that have been misdiagnosed as TCC shudder. For diagnosis of the following items, refer to the appropriate systems of the diagnostic/repair information and Computers and Control Systems Information.

- Spark plugs - check for cracks, high resistance or broken insulators
- Spark plug wires
- Fuel injector - filter may be plugged
- Fuel contamination - engine driveability concerns
- EGR valve - valve may let in too much exhaust gas and cause engine to run lean
- Vacuum leak - engine will not get correct air/fuel mixture
- Manifold Absolute Pressure (MAP) and Mass Air Flow (MAF) sensor - incorrect air/fuel mixture
- Heated Oxygen Sensor (HO2S) - too rich/lean air/fuel mixture
- Fuel pressure - may be too low
- Engine mounts - loose/damaged mounts can cause vibration concerns
- Axle joints - check for vibration