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Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Install scan tool. Check for DTCs. Is a DTC P0450 or P0451 present? If yes, go to DTC P0450: FUEL TANK PRESSURE SENSOR CIRCUIT  and DTC P0451: FUEL TANK PRESSURE SENSOR PERFORMANCE . If no, go to next step.
  3. Review freeze frame/failure records. Diagnose DTC captured in freeze frame/failure records first. Is DTC P0440 captured in freeze frame/failure records? If yes, go to next step. If no, go to step DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  4. Check EVAP system for the following conditions:
    • A loose, missing, or damaged service port Schrader valve.
    • A loose, incorrect, missing, or damaged fuel fill cap.
    • A damaged EVAP purge solenoid.
    Raise and support vehicle on a hoist. Check EVAP system for the following conditions:
    • Any disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses.
    • A damaged EVAP vent solenoid or EVAP canister.
    Did you find and correct the condition? If yes, go to step  44. If no, go to next step.
  5. Command EVAP purge solenoid ON and OFF using scan tool. Do you hear or feel a click as EVAP purge solenoid is commanded ON and OFF? If yes, go to next step. If no, go to step  8.
  6. Command EVAP vent solenoid ON and OFF using scan tool. Do you hear or feel a click as EVAP vent solenoid is commanded ON and OFF? If yes, go to next step. If no, go to step  10.
  7. Command EVAP pressure switching solenoid ON and OFF using scan tool. Do you hear or feel a click as EVAP pressure switching solenoid is commanded ON and OFF? If yes, go to step  14. If no, go to step  12.
  8. Disconnect EVAP purge solenoid. Turn ignition switch to RUN position, engine OFF. Connect test light between ignition positive voltage circuit of EVAP purge solenoid and a known-good ground. Does test light illuminate? If yes, go to next step. If no, go to step  35.
  9. Connect a test light between ignition positive voltage circuit of EVAP purge solenoid and control circuit of EVAP purge solenoid. Command EVAP purge solenoid ON using scan tool. Does the test light illuminate when EVAP purge solenoid is commanded ON and turn OFF when EVAP purge solenoid is commanded OFF? If yes, go to step  27. If no, go to step  24.
  10. Turn ignition switch to RUN position, engine OFF. Disconnect EVAP vent solenoid. Connect a test light between EVAP vent solenoid ignition positive voltage circuit and a known-good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  35.
  11. Connect a test light between EVAP vent solenoid ignition positive voltage circuit and control circuit of EVAP vent solenoid. Using scan tool, command EVAP vent solenoid ON. Does test light illuminate when EVAP vent solenoid is commanded ON and turn OFF when EVAP vent solenoid is commanded OFF? If yes, go to step  28. If no, go to step  25.
  12. Turn ignition switch to RUN position, engine OFF. Disconnect EVAP pressure switching solenoid. Connect test light between EVAP pressure switching solenoid ignition positive voltage circuit and a known-good ground. Does test light illuminate? If yes, go to next step. If no, go to step  35.
  13. Connect test light between EVAP pressure switching solenoid ignition positive voltage circuit and EVAP pressure switching solenoid control circuit. Using scan tool, command EVAP pressure switching solenoid ON. Does test light illuminate when EVAP pressure switching solenoid is commanded ON and turn OFF when EVAP pressure switching solenoid is commanded OFF? If yes, go to step  29. If no, go to step  26.
    14. NOTE: Ensure vehicle underbody temperature is similar to ambient temperature and allow surrounding air to stabilize before starting diagnostic procedure. System flow will be less with higher temperatures.
  14. Connect nitrogen/smoke supply hose of Evaporative Emission System Tester (EEST - J 41413-200), or equivalent, to EVAP service port. Turn nitrogen/smoke valve on control panel to SMOKE. Use remote switch to introduce smoke into EVAP system. Continue to introduce smoke until a steady flow of smoke is seen exiting the EVAP canister drain hose. See Fig 1. Plug EVAP canister drain hose using Plug (J 41413-301), or equivalent. Turn nitrogen/smoke valve on control panel to NITROGEN. Use remote switch to introduce Nitrogen gas into EVAP system for 60 seconds. Check entire EVAP system for exiting smoke with High Intensity White Light (J 41413-SPT), or equivalent. Continue to introduce smoke, then Nitrogen, at 60 second intervals, until source of leak has been located. Did you locate and repair a leak source? If yes, go to step  44. If no, go to next step.
  15. Remove fuel fill cap. Observe FTP sensor using scan tool. Is FTP sensor near 0.09 in. H2O? If yes, go to next step. If no, go to step  30.
  16. Install fuel fill cap on fuel fill pipe. Turn EEST nitrogen/smoke valve on control panel to NITROGEN. Use EEST to pressurize 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  19.
  17. Use remote switch to stop introducing nitrogen into EVAP system. Command EVAP purge solenoid ON. Is FTP sensor parameter less than one in. H2O? If yes, go to step  21. If no, go to next step.
  18. Disconnect EVAP purge vacuum source from EVAP purge solenoid. Is FTP Sensor parameter less than one in. H2O? If yes, go to step  34. If no, go to step  39.
  19. Disconnect EVAP canister vapor line. Does EEST gauge indicate zero in. H2O? If yes, go to step  36. If no, go to next step.
  20. Disconnect EVAP canister purge line. Does EEST gauge indicate zero in. H2O? If yes, go to step  23. If no, go to step  37.
  21. Disconnect EVAP solenoid vent hose at EVAP canister. Command EVAP vent solenoid ON (closed). Install a vacuum pump to vent hose, and apply a vacuum. Did you achieve a vacuum? If yes, go to next step. If no, go to step  32.
  22. Command EVAP vent solenoid OFF (open). Does vacuum decrease? If yes, go to next step. If no, go to step  33.
  23. Check for a faulty EVAP canister. See EVAPORATIVE EMISSION CONTROL SYSTEM DIAGNOSIS under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 1.8L VIBE article. Did you replace EVAP canister? If yes, go to step  44. If no, go to step  38.
  24. Check EVAP purge solenoid control circuit for an open, short to ground, or short to voltage. Did you find and correct the condition? If yes, go to step  44. If no, go to step  38.
  25. Check EVAP purge solenoid control circuit for an open, short to ground, or short to voltage. Did you find and correct the condition? If yes, go to step  44. If no, go to step  31.
  26. Check EVAP pressure switching solenoid control circuit for an open, short to ground or short to voltage. Did you find and correct the condition? If yes, go to step  44. If no, go to step  31.
  27. Check EVAP canister purge solenoid for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step  44. If no, go to step  39.
  28. Check EVAP vent solenoid for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step  44. If no, go to step  40.
  29. Check EVAP pressure switching solenoid for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step  44. If no, go to step  41.
  30. Check FTP sensor for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step  44. If no, go to step  42.
  31. Check PCM for an intermittent and for a poor connection. Did you find and correct the condition? If yes, go to step  44. If no, go to step  43.
  32. Check for a leak source in EVAP solenoid vent hose. Repair as necessary. Did you find and correct the condition? If yes, go to step  44. If no, go to step  40.
  33. Check for a pinched or obstructed EVAP vent hose. Repair as necessary. Did you find and correct the condition? If yes, go to step  44. If no, go to step  40.
  34. Repair pinched or obstructed EVAP purge solenoid vacuum source. After repair, go to step  44.
  35. Repair open or short to ground in EVAP solenoid ignition positive voltage circuit. Replace fuse as necessary. After repair, go to step  44.
  36. Repair restriction in EVAP vapor pipe. After repair, go to step  44.
  37. Repair restriction in EVAP purge pipe. After repair, go to step  44.
  38. Was a DTC P0446 also set? If yes, go to DTC P0446: EVAP VENT SYSTEM PERFORMANCE . If no, go to DIAGNOSTIC AIDS 
  39. Replace EVAP purge solenoid. After repair, go to step  44.
  40. Replace EVAP vent solenoid. After repair, go to step  44.
  41. Replace pressure switching solenoid. After repair, go to step  44.
  42. Replace FTP sensor. After repair, go to step  44.
  43. Replace PCM. After repair, go to next step.
    44. NOTE: Ensure vehicle underbody temperature is similar to ambient temperature and allow surrounding air to stabilize before starting the diagnostic procedure. System flow will be less with higher temperatures.
  44. Connect nitrogen/smoke supply hose of EEST to EVAP service port. Plug EVAP canister drain hose using Plug (J 41413-301), or equivalent. See Fig 1. Turn nitrogen/smoke valve to NITROGEN. Pressurize EVAP system to 5 in. H2O. Observe EEST pressure/vacuum gauge for 5 minutes. Does pressure/vacuum gauge remain constant? If yes, go to next step. If no, go to step  14.
  45. Using scan tool, observe CAPTURE INFO. Are there any DTCs that have not been diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
Fig 1: Identifying EVAP Components & Hose Routing
G00180693Courtesy of GENERAL MOTORS CORP.
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