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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls Self-Diagnostics - 4.3L >> Diagnostic Tests >> DTC P0440: EVAP System - Large Leak >> 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. 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  17. If no, go to next step.

  4. With a scan tool, capture and record the Failure Records data and clear the DTCs. Perform the Service Bay Test. See INSPECTION/MAINTENANCE EVAPORATIVE EMISSION SYSTEM SET PROCEDURE  under SELF-DIAGNOSTIC SYSTEM. Does the scan tool indicate that the Service Bay Test passed? If yes, see DIAGNOSTIC AIDS . If no, go to next step.
    5. NOTE: Always zero the EVAP pressure and vacuum (in. H2O) gages on the J 41413 EVAP Pressure/Purge Diagnostic Station before proceeding with diagnosis.
  5. 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 gage for 1 minute. Did you obtain and hold 5 in. H2O? If yes, go to next step. If no, go to step  8.
  6. 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  13.
  7. With the J 41413, pressurize the EVAP system to 5 in. H2O. Rotate the J 41413 rotary valve to the OFF/HOLD position. Monitor the pressure gage on J 41413. With a scan tool, command the EVAP canister purge valve to 50 percent. Does the EVAP system pressure decrease? If yes, go to step  9. If no, go to step  10.
    8. NOTE: The fuel tank may need to be partially lowered in order to inspect components located in the upper portion of the tank.
  8. 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  17. If no, see DIAGNOSTIC AIDS .

  9. Disconnect the EVAP purge pipe from the EVAP canister purge valve. Install the J 41413 vacuum hose on the EVAP canister purge valve port. Start the engine. Run the engine between 1200-1500 RPM. With a scan tool command the EVAP canister purge valve to 50 percent. Does the EVAP pressure/purge diagnostic station vacuum gage measure above 12 in. Hg? If yes, see DIAGNOSTIC AIDS . If no, go to step  15.
  10. Monitor the pressure gage 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  15. If no, go to next step.
  11. Monitor the pressure gage on the J 41413. Disconnect the purge pipe at the EVAP canister. Does the EVAP system pressure decrease? If yes, see EVAPORATIVE EMISSION SYSTEM CLEANING in REMOVAL, OVERHAUL & INSTALLATION. If no, go to next step.
  12. Monitor the pressure gage on the J 41413. Disconnect the EVAP vapor line from the EVAP canister. Does the EVAP system pressure decrease? If yes, go to step  16. If no, go to step  14.
  13. Replace the FTP sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  17.
  14. Repair for a pinched or obstructed EVAP vapor pipe. After repairs, go to step  17.
  15. Replace the EVAP purge valve. After repairs, go to step  17.
  16. Replace the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to next step.
  17. Perform the Service Bay Test. See INSPECTION/MAINTENANCE EVAPORATIVE EMISSION SYSTEM SET PROCEDURE  under SELF-DIAGNOSTIC SYSTEM. Does the scan tool indicate that the Service Bay Test passed? If yes, go to next step. If no, go to step  5.
  18. 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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