Transmission Stall Speed Test. Diagnosis and Testing

Stall Speed Test

To prevent damage to transmission components, the PCM will reduce engine output torque when a stall condition exists. Due to this torque reduction, the stall test cannot be used as a diagnostic test to determine the condition of the transmission clutches.

The PCM monitors clutch operation and sets one or more DTCs when undesired slippage is detected.

The torque converter stator one-way clutch should hold during idle and during acceleration. A one-way clutch malfunction can be determined if all of the following conditions/symptoms are present:

• Transmission fluid is clean and not excessively contaminated
• Normal/expected vehicle performance at cruising speed
• Poor engine idle quality. The engine may even stall
• Very poor acceleration/lack of power
• Very low stall speed: <1500 rpm. Perform the test procedure below:

1. 1
   Apply the parking brake.
2. 2
   Connect the scan tool. Go to Data Logger: PCM
3. 3
   Monitor PIDs: APP (%), RPM, LOAD (%) and GEAR_CMD.
4. 4
   Start the engine.
5. 5
   Select the Reverse gear range.
6. 6
   Start the data logger recording.
7. 7
   With the brake pedal firmly applied, depress the accelerator pedal to 100% for 2-3 seconds, until engine speed stabilizes. Release the accelerator pedal.
8. 8
   Place the transmission in the Neutral position.
9. 9
   Press the accelerator pedal to maintain 1500 rpm for 10 seconds to allow the torque converter to cool. Release the accelerator pedal.
10. 10
    Shift into gear.
11. 11
    With the brake pedal firmly applied, depress the accelerator pedal to 100% for 2-3 seconds, until engine speed stabilizes. Release the accelerator pedal.
12. 12
    Place the transmission in the Neutral position.
13. 13
    Press the accelerator pedal to maintain 1500 rpm for 10 seconds to allow the torque converter to cool. Release the accelerator pedal.
14. 14
    Turn the engine off.
15. 15
    Review the record. A properly functioning stator one-way clutch must meet the following specifications:
    

    • APP = 100%

    • RPM > 1500

    • LOAD < 100%

    • GEAR_CMD = Reverse or 1st gear command