Torque Converter Diagnosis
Torque Converter Diagnosis
WARNING: If equipped with fire suppression system, refer to Fire Suppression System for Important Safety Warnings. Failure to follow this instruction may result in serious personal injury. Description and Operation
NOTE: Always drive the vehicle in a safe manner according to the driving conditions and obey all traffic laws.
The Torque Converter Operation Test provide diagnostic information on the transmission torque converter operation.
Prior to new torque converter installation, 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 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. Carry out diagnostic procedures.
- Carry out On-Board Diagnostic (OBD); refer to Diagnostics Diagnostics.
- Repair all non-transmission related DTCs first.
- Repair all transmission DTCs.
- Rerun OBD to verify repair.
- Carry out Line Pressure Test. Refer to Special Testing Procedures Special Testing Procedures.
- Carry out Stall Speed Test. Refer to Special Testing Procedures Special Testing Procedures.
- Carry out Diagnostic Routines. Refer to Diagnosis By Symptom Diagnosis By Symptom.
- Use the Diagnosis by Symptom Chart 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
This test verifies that the Torque Converter Clutch (TCC) control system and the torque converter are operating correctly.
1. Carry out Self Test with scan tool. Refer to the Computers and Control Systems. Check for DTCs.
2. Connect the scan tool.
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 the brake pedal is tapped, and decrease about 5 seconds after the pedal is released. If this does not occur, see torque converter operation concerns. Refer to Diagnosis By Symptom Diagnosis By Symptom.
6. If the vehicle stalls in (D) or manual 2 at idle with vehicle at a stop, move the transmission selector lever to the manual 1 position. If the vehicle stalls, see torque converter operation concerns. Refer to Diagnosis By Symptom Diagnosis By Symptom. If the vehicle does not stall in (D), refer to Diagnosis By Symptom Diagnosis By Symptom.
7. If the vehicle exhibits a vibration during the road test complete the Torque Converter Road Evaluation Form. This form will aid the technician in determining the source of the vibration.
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 information.
- Spark plugs - check for cracks, high resistance or broken insulators.
- Ignition coil-on-plug - short or open circuit.
- Fuel injector - filter may be plugged.
- Fuel contamination - engine runs poor.
- 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)/Mass Air Flow (MAF) sensor - improper 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.
