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Home >> Chevrolet >> 2002 >> Impala LS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 3.8L >> Diagnostic Tests >> DTC P0440: EVAP System >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing Diagnostic System Check - Engine Controls, go to next step.
  2. Does the scan tool indicate DTC P0443 or DTC P0449 are also set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Inspect EVAP system for the following conditions:
    • Loose, missing, or damaged service port Schrader valve.
    • Loose, incorrect, missing, or damaged fuel fill cap.
    • 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  19. If no, go to next step.

  4. With a scan tool, capture and record the fail record data and clear the DTCs. Perform the SERVICE BAY TEST using scan tool. 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 EVAP pressure and vacuum (in. H2O) gauges on EVAP pressure and purge station before proceeding with diagnosis.
  5. Install Fuel Tank Cap Adapter (J 41415-40). Connect EVAP Pressure and Purge Station (J 41413) and vehicle fuel fill cap to fuel tank cap adapter. Turn ignition on, engine off. Using scan tool, seal EVAP system. Using EVAP pressure and purge station, pressurize system to 5 in. H2O. Rotate EVAP pressure and purge station rotary switch to OFF/HOLD position. Monitor pressure gauge for one minute. Was 5 in. H2O obtained and held? If yes, go to next step. If no, go to step  8.
  6. Compare the EVAP pressure and purge station value to the scan tool FTP sensor value. Does EVAP pressure and purge station value measure near the scan tool value? If yes, go to next step. If no, go to step  12.
  7. Monitor pressure gauge on EVAP pressure and purge station. Disconnect EVAP purge pipe from EVAP purge valve. Does the EVAP system pressure decrease? If yes, go to step  9. If no, go to step  10.
    8. NOTE: Fuel tank may need to be partially lowered to inspect components located in upper portion of tank.
  8. Using EVAP pressure and purge station, continuously pressurize EVAP system. Using Ultrasonic Leak Detector (J 41416), inspect for leaks in the following locations:
    • EVAP system purge pipe.
    • EVAP vapor pipe.
    • EVAP vent hose/pipe.
    • Fuel fill pipe/hose and fuel fill cap.
    • EVAP canister.
    • EVAP canister vent valve.
    • EVAP canister purge valve.
    • Fuel sender assembly and/or seal.
    • FTP sensor seal.
    • Fill limiter vent valve, pressure relief valve, rollover valve, or fuel tank.

    Did you find and correct the condition? If yes, go to step  19. If no, see DIAGNOSTIC AIDS .

  9. Attach a vacuum gauge to EVAP purge valve purge pipe port. Start engine and allow engine to idle. Using scan tool, command EVAP purge valve to 50 percent. Does the vacuum gauge show vacuum more than 10 in. H2O? If yes, see DIAGNOSTIC AIDS . If no, go to step  13.
  10. Monitor pressure gauge on EVAP pressure and purge station. Disconnect EVAP purge pipe from EVAP canister. Does the EVAP system pressure decrease? If yes, go to step  15. If no, go to next step.
  11. Monitor pressure gauge on EVAP pressure and purge station. Disconnect the EVAP vapor pipe from the EVAP canister. Does the EVAP system pressure decrease? If yes, go to step  18. If no, go to step  14.
  12. Using scan tool, monitor FTP sensor voltage. Is FTP sensor voltage more than 4.3 volts? If yes, see DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE . If no, go to step  16.
  13. Check vacuum source to EVAP purge valve for blockage, cuts, or disconnects. Repair as necessary. Did you find and correct the condition? If yes, go to step  19. If no, go to step  17.
  14. Repair pinched or obstructed EVAP vapor pipe. After repairs, go to step  19.
  15. Repair restriction in EVAP purge pipe. After repairs, go to step  19.
  16. Replace FTP sensor. After repairs, go to step  19.
  17. Replace EVAP purge valve. After repairs, go to step  19.
  18. Replace EVAP canister. After repairs, go to step  19.
  19. With a scan tool, capture and record the fail record data and clear the DTCs. Perform the SERVICE BAY TEST using scan tool. Does the scan tool indicate that the service bay test passed? If yes, go to next step. If no, go to step  5.
  20. Using scan tool, observe stored information. Does scan tool displays any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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