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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls - Self-Diagnostics - 4.3L >> Diagnostic Tests >> DTC P0455: Evaporative Emission Control System Leak Detected (Gross Leak/No Flow) >> Diagnostic Procedures

Diagnostic Procedures

  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Inspect the evaporative emission (EVAP) system for loose, missing, or damaged service port Schrader valve. Inspect for loose, incorrect, missing, or damaged fuel fill cap, or a damaged EVAP purge solenoid. Raise vehicle on a hoist. Inspect the EVAP system for disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses. Inspect for damaged EVAP vent solenoid or EVAP canister. Did you find and correct the condition? If yes, go to step  16. If no, go to next step.
    3. 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.
  3. 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 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  16. If no, go to next step.
  4. Disconnect the Fuel Tank Cap Adapter from the fuel fill pipe. Install the 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 the 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  16. If no, go to next step.
  5. 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 and 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 the scan tool fuel tank pressure sensor parameter within 1 in. H2O of the pressure/vacuum gauge? If yes, go to next step. If no, go to step  12.
  6. 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 13 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  12.
  7. 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.
  8. 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  13. If no, go to next step.
  9. Disconnect the EVAP purge pipe at the EVAP canister. Is the fuel tank pressure sensor parameter less than 1 in. H2O? If yes, go to step  14. If no, go to next step.
  10. Disconnect the EVAP vapor pipe at the EVAP canister. Is the fuel tank pressure sensor parameter less than 1 in. H2O? If yes, go to step  15. If no, go to next step.
  11. Repair pinched or obstructed EVAP vapor pipe. After repairs, go to step  16.
  12. Replace FTP sensor. After replacing sensor, go to step  16.
  13. Replace EVAP purge solenoid. After replacing solenoid, go to step  16.
  14. Repair restriction in the EVAP purge pipe. After repairs, go to step  16.
  15. Replace EVAP canister. After replacing EVAP canister, go to next step.
    16. NOTE: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
  16. 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  3.
  17. Observe the fuel tank pressure sensor parameter with a scan tool. Is the scan tool fuel tank pressure 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  5.
  18. Replace PCM. See appropriate REMOVAL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  19. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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