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P code powertrain Medium severity

P1408 EGR Flow Out Of Self Test Range

The OBD2 code P1408 indicates that the Engine Control Module (ECM) has detected that the EGR (Exhaust Gas Recirculation) flow is outside the expected range during a self-test, suggesting a potential issue with the EGR...

Definition

The OBD2 code P1408 indicates that the Engine Control Module (ECM) has detected that the EGR (Exhaust Gas Recirculation) flow is outside the expected range during a self-test, suggesting a potential issue with the EGR system's performance or components

Common causes

  • Faulty EGR valve
  • Blocked EGR passages
  • Vacuum leaks
  • Faulty EGR position sensor
  • Wiring issues or poor connections
  • Malfunctioning PCM (Powertrain Control Module)
  • Carbon buildup in the EGR system
  • Incorrectly installed or damaged EGR components

Common misdiagnoses

  • Faulty EGR valve
  • Clogged EGR passages
  • Vacuum leaks
  • Faulty EGR pressure sensor
  • Faulty engine control module (ECM)
  • Incorrectly installed EGR system components
  • Exhaust leaks
  • Faulty intake manifold pressure sensor

Troubleshooting steps

  1. 1. Check for Additional Codes

    Before proceeding, check for any other related trouble codes that may provide more context or indicate other issues with the EGR system or related components

  2. 2. Inspect the EGR Valve

  3. 3. Visually inspect the EGR valve for any signs of damage, carbon buildup, or blockage

  4. 4. Ensure that the valve is not stuck open or closed

  5. 5. Test the EGR Valve Operation

  6. 6. Use a scan tool to command the EGR valve to open and close. Observe the response to ensure it operates correctly

  7. 7. If the valve does not respond as expected, it may need to be replaced

  8. 8. Check EGR System Components

  9. 9. Inspect the EGR passages for blockages or restrictions. Carbon buildup can impede flow

  10. 10. Check the EGR solenoid (if equipped) for proper operation and ensure it is receiving the correct signals from the ECM

  11. 11. Inspect Vacuum Lines

  12. 12. If the EGR system is vacuum-operated, check for any leaks or cracks in the vacuum lines that could affect EGR operation

  13. 13. Test the EGR Pressure Feedback Sensor (if applicable)

  14. 14. Some vehicles have a pressure feedback sensor that monitors EGR flow. Test the sensor for proper operation and check for any wiring issues

  15. 15. Check for Exhaust Leaks

  16. 16. Inspect the exhaust system for leaks that could affect EGR flow readings. A leak can cause incorrect readings and trigger the code

  17. 17. Inspect Electrical Connections

  18. 18. Check the wiring and connectors related to the EGR system for corrosion, damage, or loose connections

  19. 19. Clear the Code and Test Drive

  20. 20. After performing any repairs or adjustments, clear the trouble code using a scan tool and take the vehicle for a test drive to see if the code returns

  21. 21. If the issue persists, refer to the vehicle's service manual for specific diagnostic procedures and specifications related to the EGR system. 1

  22. 22. Professional Diagnosis

  23. 23. If you are unable to resolve the issue, consider seeking help from a professional mechanic who has experience with EGR system diagnostics. By following these steps, you should be able to identify and address the cause of the P1408 code