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 unit off for correct test results. For a description of PTO operation, refer to Transmission Electronic Control System.

During PTO operation, the on-board diagnostics will be disabled. However, the circuit checks made by the diagnostic system and the FMEM will continue. The PTO must be turned off to do on-board diagnostics.
Begin with the normal diagnostic procedures as follows:

1. Preliminary Inspection.
2. Know and Understand the Customer's Concern.
3. Verify the Concern - Carry out the Torque Converter Clutch Operation Test.
4. Carry out Diagnostic Procedures.
^ Run on-board diagnostics. Refer to On-Board Diagnostics with diagnostic tool. Displaying & Reading Trouble Codes
^ Repair all non-transmission-related DTCs first.
^ Repair all transmission DTCs.
^ Rerun on-board diagnostics to verify repair.
^ Carry out Line Pressure Test. Line Pressure Test
^ Carry out Stall Speed Test. Stall Speed Test
^ Carry out Diagnostic Routines. 4R100
^ 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. 4R100

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, refer to On-Board Diagnostics with diagnostic tool. Check for DTCs, refer to the Diagnostic Trouble Code Chart. Trouble Code to Pinpoint Test Charts
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 (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 brake pedal is tapped and decrease about five seconds after pedal is released. If this does not occur, refer to Diagnosis By Symptom - Torque Converter Clutch Operation Concerns. Torque Converter Clutch Operation Concern 240-242/340-324
6. If the vehicle stalls in (D) or MANUAL 2 at idle with vehicle at a stop, move the transmission range selector lever to MANUAL 1 position. If the vehicle stalls, refer to Diagnosis By Symptom - Torque Converter Clutch Operation Concerns. Repair as required. If the vehicle does not stall in (D), refer to Diagnosis By Symptom. 4R100