Torque Converter Operation Test
4R70E/4R75E
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 Computers and Control Systems Information. 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 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 systems of the diagnostic/repair information and Computers and Control Systems 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.
