Preliminary Tests
ROAD TESTING VEHICLEThe following Shift Point Road Test and Torque Converter Clutch Operation Test provide diagnostic information on transmission shift controls and torque converter operation.
SHIFT POINT ROAD TEST
NOTE: Always drive the vehicle in a safe manner according to driving conditions and obey all traffic laws.
This test verifies that the shift control system is operating properly.
1. Bring engine and transmission up to normal operating temperature.
2. Operate the vehicle with the transmission range selector lever in (D).
3. Apply minimum throttle and observe the speeds at which the upshift occurs and the torque converter engages.
4. With the transmission in OVERDRIVE (fourth gear), depress the transmission control switch. The transmission should downshift to third gear. Remove foot from accelerator pedal; engine braking should occur.
5. Press the accelerator pedal to floor (wide-open throttle). The transmission should shift from third to second gear or third to first, depending on vehicle speed. Torque converter clutch should disengage and then reapply.
6. With vehicle (D) range above 80 km/h (50 mph) and less than half throttle, move the transmission range selector lever from (D) range to MANUAL 2 range and remove foot from the accelerator pedal. The transmission should immediately downshift into second gear. With the vehicle remaining in MANUAL 2 range, move the transmission range selector lever into MANUAL 1 range. Transmission should downshift into first gear at speeds below 48-56 km/h (30-35 mph).
7. If the transmission fails to upshift/downshift or the torque converter clutch does not apply and release, refer to Diagnosis by Symptom Index.
APPLICATIONS SHIFT SPEEDS-APPROXIMATE* MPH
NOTE: Vehicles equipped with an OSS sensor will have new adaptive shift strategies. Whenever the vehicles battery has been disconnected for any type of service or repairs the strategy parameters that are stored in the Keep Alive Memory (KAM) will be lost. The strategy will start to learn once the battery is reconnected and the vehicle is driven. This is a normal condition and will go away once the PCM learns all the parameters from the driving conditions. There is no time frame set to this learning process. If this concern is present during down shifts or converter clutch apply, it is not the shift strategy and will require diagnosis. The customer needs to be notified that they may experience slightly different upshifts either soft or firm and that this condition is normal and will eventually go away.
NOTE: D is the same as (D) with the transmission control switch actuated (light on).
*(1) Nominal shift speed at sea level is shown. Actual shift speed will depend on tire size, brand, and altitude.
TORQUE CONVERTER DIAGNOSIS
Prior to torque converter replacement, 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 replace the torque converter.
Begin with the normal diagnostic procedures as follows:
1. Preliminary Inspection.
2. Know and Understand the Customer's Concern.
3. Verify the Concern-Perform the Torque Converter Clutch Operation Test.
4. Perform Diagnostic Procedures.
- Run on-board diagnostics.
- Repair all non-transmission-related Des first.
- Repair all transmission Des.
- Rerun on-board diagnostics to verify repair.
- Perform Line Pressure Test.
- Perform Stall Speed Test.
- Perform Diagnostic Routines.
- 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.
TORQUE CONVERTER OPERATION TEST
This test verifies that the torque converter clutch control system and the torque converter are operating properly.
1. Perform Quick Test. Check for codes.
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. 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 Torque Converter Clutch Operation Concerns in the Diagnosis by Symptom Index.
5. 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 Torque Converter Clutch Operation Concerns in the Diagnosis by Symptom Index. Repair as required. If the vehicle does not stall in (D), refer to Diagnosis by Symptom Index.