6HP26 - Automatic Transaxle/Transmission

Torque Converter Diagnosis
Prior to torque converter installation, all diagnostic procedures must be followed. This is to prevent the unnecessary replacement 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. Preliminary Inspection
2. Know and understand the customer's concern.
3. Verify the condition - carry out the torque converter operation test.
4. Carry out diagnostic procedures.
^ Carry out On-Board Diagnostics. Refer to Diagnostics. Diagnostics
- Repair all non-transmission related DTCs first.
- Repair all transmission DTCs.
- Rerun on-board diagnostic to verify repair.
^ Carry out Stall Speed Test. Refer to Special Testing Procedures. Stall Speed Special Testing Procedures
^ Carry out 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. Diagnosis By Symptom

Torque Converter Operation Test
This test verifies that the torque converter clutch control system and the torque converter are operating correctly.
1. Carry out Quick Test with scan tool. Refer to Computers and Control Systems. Check for DTCs.
2. Connect a tachometer to the engine.
3. Bring the engine to normal operating temperature by driving the vehicle at highway speeds for approximately 15 minutes in DRIVE position.
4. After normal operating temperature is reached, maintain a constant 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 DRIVE or at idle with the vehicle at a stop, move the transmission range selector lever to the manual 1 position. If the vehicle stalls, see Torque Converter Operation Concerns. Refer to Diagnosis By Symptom. If the vehicle does not stall in DRIVE, refer to Diagnosis By Symptom. Diagnosis By Symptom

NOTE: The following is a list of common vehicle concerns that have been misdiagnosed as torque converter clutch shudder. For diagnosis of the following items, refer to Computers and Control Systems.

^ Spark plugs - check for cracks, high resistance or broken insulators
^ 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)/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