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Home >> Pontiac >> 2002 >> Aztek FWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0440: EVAP System - Large Leak >> Diagnostic Procedures
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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. Does the scan tool indicate DTC P0443 or DTC P0449 are also set? If yes, see DTC P0443: EVAP PURGE SOLENOID CONTROL CIRCUIT  or DTC P0449: EVAP VENT VALVE PERFORMANCE  . If no, go to next step.
  3. Inspect the EVAP system for the following conditions:
    • Loose, missing, or damaged service port Schrader valve.
    • Loose, incorrect, missing, or damaged fuel fill cap.
    • A damaged EVAP canister purge valve.

    Raise the vehicle on a hoist. Inspect the EVAP system for the following conditions:

    • Disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses.
    • A damaged EVAP canister vent valve or EVAP canister.

    Did you find and correct the condition? If yes, go to step  18. If no, go to next step.

    4. NOTE: Always zero the EVAP pressure and vacuum (in. H2O) gauges on the J 41413 EVAP Pressure/Purge Diagnostic Station before proceeding with diagnosis.
  4. Install the J 41415-40 Fuel Fill Cap Adapter. Connect the J 41413 and the vehicle fuel fill cap to the J 41415-40. Turn ON the ignition, with the engine OFF. With the scan tool, seal the EVAP system. With the J 41413, pressurize the system to 5 in. H2O. Rotate the J 41413 rotary switch to the OFF/HOLD position. Monitor the pressure gauge for 1 minute. Did you obtain and hold 5 in. H2O? If yes, go to next step. If no, go to step  7.
  5. Compare the J 41413 value to the scan tool FTP value. Does EVAP pressure/purge diagnostic station value measure near the scan tool value? If yes, go to next step. If no, go to step  11.
  6. Monitor the pressure gauge on the J 41413. Disconnect the EVAP purge pipe from the EVAP purge valve. Does the EVAP system pressure decrease? If yes, go to step  8. If no, go to step  9.
    7. NOTE: The fuel tank may need to be partially lowered in order to inspect components located in the upper portion of the tank.
  7. With the J 41413, continuously pressurize the EVAP system. With the J 41416 Ultrasonic Leak Detector, inspect for leaks in the following locations:
    • The EVAP system purge pipe.
    • The EVAP vapor pipe.
    • The EVAP vent hose/pipe.
    • The fuel fill pipe/hose and fuel fill cap.
    • The EVAP canister.
    • The EVAP canister vent valve.
    • The EVAP canister purge valve.
    • The fuel sender assembly and/or seal.
    • The FTP sensor seal.
    • The fill limiter vent valve, pressure relief valve, rollover valve, or fuel tank.

    Did you locate and repair the system? If yes, go to step  18. If no, see DIAGNOSTIC AIDS .

  8. Attach a vacuum gauge to the purge pipe port of the EVAP purge valve. Start the engine and allow the engine to idle. Command the EVAP purge valve to 50 percent with a scan tool. Does the vacuum gauge show vacuum more than 10 in. H2O? If yes, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM. If no, go to step  12.
  9. Monitor the pressure gauge on EVAP pressure/purge diagnostic station. Disconnect the EVAP purge pipe from the EVAP canister purge valve. Does the EVAP system pressure decrease? If yes, go to step  14. If no, go to next step.
  10. Monitor the pressure gauge on EVAP pressure/purge diagnostic station. Disconnect the purge pipe at the EVAP canister. Does the EVAP system pressure decrease? If yes, go to step  17. If no, go to step  13.
  11. Monitor the FTP sensor voltage with a scan tool. Is the FTP sensor voltage more than 4.3 V? If yes, see DTC P0453: FUEL TANK PRESSURE SENSOR - HIGH VOLTAGE . If no, go to step  15.
  12. Inspect the vacuum source to the EVAP purge valve for blockage, cuts, or disconnects. Repair as necessary. Did you find and correct the condition? If yes, go to step  18. If no, go to step  16.
  13. Repair pinched or obstructed EVAP vapor pipe. After repairs, go to step  18.
  14. Repair the restriction in the EVAP purge pipe. After repairs, go to step  18.
  15. Replace the FTP sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  18.
  16. Replace the EVAP canister purge valve. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  18.
  17. Replace the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
    18. NOTE: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
  18. Turn ON the ignition, with the engine OFF. Command the EVAP canister vent valve ON with a scan tool. Pressurize the EVAP system to 5 in. H2O with the J 41413. Place the control knob on the J 41413 to the OFF/HOLD position. Monitor the EVAP system pressure on the J 41413 for 5 minutes. Does the EVAP system pressure remain constant? If yes, go to next step. If no, go to step  7.
  19. Monitor the pressure gauge on the J 41413. Command the EVAP purge valve to 50 percent with a scan tool. Does the EVAP system pressure decrease? If yes, go to next step. If no, go to step  9.
  20. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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