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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 263 (ENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L)DIAGNOSTIC TESTSDTC P0440: EVAP SYSTEMDIAGNOSTIC PROCEDURES
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Diagnostic Procedures

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2003 GMC Sonoma and 2003 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Inspect EVAP system for loose, missing, or damaged service port Schrader valve. Check for loose, incorrect, missing, or damaged fuel fill cap. Check for damaged EVAP canister purge valve. Raise the vehicle on a hoist. Inspect the EVAP system for disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses. Check for damaged EVAP canister vent valve or EVAP canister. Did you find and correct the condition? If yes, go to step  34 . If no, go to next step.
  3. Use scan tool in order to clear the DTCs. Command the EVAP canister purge valve to 50 percent and back to zero percent with scan tool. Do you hear or feel a clicking from the EVAP purge valve when it is commanded to 50 percent? If yes, go to next step. If no, go to step  5 .
  4. Command the EVAP canister vent valve ON and OFF with the scan tool. Do you hear or feel a click as the EVAP vent valve is commanded ON and OFF? If yes, go to step  9 . If no, go to step  7 .
  5. Disconnect the EVAP purge valve harness connector. Turn ignition on, with engine off. Connect a test light between the ignition voltage circuit of the EVAP purge valve and a known-good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  25 .
  6. Connect a test light between the ignition voltage circuit and the control circuit of the EVAP purge valve. Command the EVAP purge valve to 50 percent and then to zero percent with a scan tool. Does the test light illuminate or pulsate when the EVAP purge valve is commanded to 50 percent and turn OFF when the EVAP purge valve is commanded to zero percent? If yes, go to step  20 . If no, go to step  18 .
  7. Turn ignition on, with engine off. Disconnect the EVAP vent valve harness connector. Connect a test light between the EVAP vent valve ignition voltage circuit and a known-good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  26 .
  8. Connect the test light between the ignition voltage circuit and the control circuit of the EVAP vent valve. Command the EVAP vent valve ON, with a scan tool. Does the test light illuminate when the EVAP vent valve is commanded ON? If yes, go to step  21 . If no, go to step  19 .
    9. NOTE: Ensure that vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. System flow will be less with higher temperatures.
  9. Turn ignition off. Connect the Evaporative Emissions System Tester (J-41413-200) power supply clips to a known-good 12-volt source. Install the Fuel Tank Cap Adapter (J-41415-40) to the fuel fill pipe. Connect the fuel fill cap to the Fuel Tank Cap Adapter. Connect the Evaporative Emissions System Tester nitrogen/smoke supply hose to the Fuel Tank Cap Adapter. Turn ignition on, with engine off. Command the EVAP vent solenoid closed with a scan tool. Turn the nitrogen/smoke valve on the Evaporative Emissions System Tester control panel to SMOKE. Use the remote switch to introduce smoke into the EVAP system. Use the EVAP Service Port Vent Fitting (J-41413-VLV) to open the EVAP service port. Remove the EVAP Service Port Vent Fitting once smoke is observed. Continue to introduce smoke into the EVAP system for an additional 60 seconds. Inspect the entire EVAP system for exiting smoke with the High Intensity White Light (J-41413-SPT). Continue to introduce smoke at 15 second intervals until the leak source has been located. Did you locate and repair a leak source? If yes, go to step  34 . If no, go to next step.
  10. Disconnect the Fuel Tank Cap Adapter from the fuel fill pipe. Install fuel fill cap to the fuel fill pipe. Connect the Evaporative Emissions System Tester nitrogen/smoke supply hose to the EVAP service port. Use the remote switch to introduce smoke into the EVAP system. Inspect entire EVAP system for exiting smoke with the High Intensity White Light. Continue to introduce smoke at 15 second intervals until the leak source has been located. Did you locate and repair a leak source? If yes, go to step  34 . If no, go to next step.
  11. Use the remote switch to stop introducing smoke. Install the Fuel Tank Cap Adapter to the fuel fill pipe. Connect the Evaporative Emissions System Tester nitrogen/smoke supply hose to the Fuel Tank Cap Adapter. Connect the vehicle fuel fill cap to the Fuel Tank Cap Adapter. Command the EVAP vent solenoid open with a scan tool. Compare the fuel tank pressure sensor parameter with a scan tool, to the Evaporative Emissions System Tester pressure/vacuum gauge. Is scan tool fuel tank pressure sensor parameter within 1 in. H2O of the Evaporative Emissions System Tester pressure/vacuum gauge? If yes, go to next step. If no, go to step  22 .
  12. Seal the EVAP system using the EVAP Purge/Seal function with a scan tool. Turn the nitrogen/smoke valve on the Evaporative Emissions System Tester control panel to NITROGEN. Use the Evaporative Emissions System Tester to pressurize the EVAP system to 10 in. H2O. Is the fuel tank pressure sensor parameter more than 5 in. H2O? If yes, go to next step. If no, go to step  22 .
  13. Use the remote switch to stop introducing nitrogen into the EVAP system. Increase the EVAP purge solenoid to 100 percent. Is the Fuel Tank Pressure Sensor parameter less than 1 in. H2O? If yes, go to DIAGNOSTIC AIDS  . If no, go to next step.
  14. Disconnect the EVAP purge vacuum source from the EVAP purge solenoid. Is the Fuel Tank Pressure Sensor parameter less than 1 in. H2O? If yes, go to step  24 . If no, go to next step.
  15. Disconnect the EVAP purge pipe from the EVAP purge solenoid. Is the fuel tank pressure sensor parameter less than 1 in. H2O? If yes, go to step  29 . If no, go to next step.
  16. Disconnect the EVAP purge pipe at EVAP canister. Is the fuel tank pressure sensor parameter less than 1 in. H2O? If yes, go to step  27 . If no, go to next step.
  17. Disconnect EVAP vapor pipe at the EVAP canister. Is the fuel tank pressure sensor parameter less than 1 in. H2O? If yes, go to step  31 . If no, go to step  28 .
  18. Test control circuit of the EVAP purge solenoid for an open or for a short to voltage. Did you find and correct the condition? If yes, go to step  34 . If no, go to step  23 .
  19. Test control circuit of the EVAP vent solenoid for an open or for a short to voltage. Did you find and correct the condition? If yes, go to step  34 . If no, go to step  23 .
  20. Test for an intermittent and for a poor connection at the EVAP canister purge solenoid. Did you find and correct the condition? If yes, go to step  34 . If no, go to step  29 .
  21. Test for an intermittent and for a poor connection at the EVAP vent solenoid. Did you find and correct the condition? If yes, go to step  34 . If no, go to step  30 .
  22. Test for an intermittent and for a poor connection at the FTP sensor. Did you find and correct the condition? If yes, go to step  34 . If no, go to step  32 .
  23. Test for an intermittent and for a poor connection at the control module. Did you find and correct the condition? If yes, go to step  34 . If no, go to step  33 .
  24. Repair pinched or obstructed EVAP purge solenoid vacuum source. After repairs, go to step  34 .
  25. Repair open or short to ground in the ignition 1 voltage circuit of the EVAP purge solenoid. Replace the fuse as necessary. After repairs, go to step  34 .
  26. Repair open or short to ground in the ignition 1 voltage circuit of the EVAP vent solenoid. Replace fuse as necessary. After repairs, go to step  34 .
  27. Repair restriction in the EVAP purge pipe. After repairs, go to step  34 .
  28. Repair restriction in the EVAP vapor pipe. After repairs, go to step  34 .
  29. Replace EVAP purge solenoid. After repairs, go to step  34 .
  30. Replace EVAP vent solenoid. After repairs, go to step  34 .
  31. Replace EVAP canister. After repairs, go to step  34 .
  32. Replace FTP sensor. After repairs, go to step  34 .
  33. Replace PCM. See appropriate REMOVAL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
    34. NOTE: Do not exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
  34. Connect the Evaporative Emissions System Tester to the fuel fill pipe. Turn the nitrogen/smoke valve to NITROGEN. Seal the EVAP system using the EVAP purge/seal function with a scan tool. Pressurize the EVAP system to 5 in. H2O. Observe the Evaporative Emissions System Tester pressure/vacuum gauge for 5 minutes. Does the pressure/vacuum gauge remain constant? If yes, go to next step. If no, go to step  2 .
  35. Using scan tool, observe stored information and capture information. Does the scan tool display any DTCs that you have not diagnosed? If yes, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, system is okay.
RENDER: 1.0x

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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.