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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 51 (Engine Control System - Self-Diagnostics - 4.2L) >> Diagnostic Tests >> DTC P0440: EVAP System - Large Leak >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. 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, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Are DTCs P0446, P0452, P0453, or P1441 also set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, go to next step.
  3. Inspect the EVAP system for the following conditions:
    • A loose, incorrect, faulty, or missing fuel tank fill cap.
    • Damaged or disconnected EVAP system purge lines.
    • A damaged EVAP system component.
    • A loose, missing, or damaged service port Schrader valve.

    Did you find and correct the condition? If yes, go to step  31 . If no, go to next step.

  4. Use the scan tool in order to clear the DTCs. Command the EVAP canister purge valve to 50 percent and back to 0 percent with the scan tool. Do you hear or feel a clicking from the EVAP purge valve when the purge valve is commanded to 50 percent? If yes, go to next step. If no, go to step  6 .
  5. Command the EVAP canister vent valve ON and OFF with the scan tool. Do you hear or feel a click as the EVAP vent valve is commanded ON and OFF? If yes, go to step  10 . If no, go to step  8 .
  6. Disconnect the EVAP purge valve harness connector. Turn ON the ignition, with engine OFF. Connect a test lamp between the ignition voltage circuit of the EVAP purge valve and a known-good ground. Does the test lamp illuminate? If yes, go to next step. If no, go to step  22 .
  7. Connect a test lamp between the ignition voltage circuit and the control circuit of the EVAP purge valve. Command the EVAP purge valve to 50 percent and then to 0 percent with a scan tool. Does the test lamp illuminate or pulsate when the EVAP purge valve is commanded to 50 percent and turn OFF when the EVAP purge valve is commanded to 0 percent? If yes, go to step  18 . If no, go to step  16 .
  8. Turn ON the ignition, with the engine OFF. Disconnect the EVAP vent valve harness connector. Connect a test lamp between the EVAP vent valve ignition voltage circuit and a good ground. Does the test lamp illuminate? If yes, go to next step. If no, go to step  23 .
  9. Connect the test lamp between the ignition voltage circuit and the control circuit of the EVAP vent valve. Command the EVAP vent valve ON with a scan tool. Does the test lamp illuminate when the EVAP vent valve is commanded ON? If yes, go to step  19 . If no, go to step  17 .
  10. Turn OFF the ignition. Disconnect the EVAP purge pipe from the EVAP purge valve. Connect a vacuum gauge directly to the EVAP purge port of the EVAP purge valve. Start and idle the engine. Command the EVAP canister purge valve to 50 percent with a scan tool. Is the vacuum equal to or more than 15 in. H2O? If yes, go to next step. If no, go to step  21 .
    11. NOTE: The following steps require the J 41413 EVAP Pressure/Purge Diagnostic Station, and the J 41415-40 Fuel Tank Cap Adapter. Always zero the EVAP pressure and vacuum (in. H2O) gauges on the EVAP pressure/purge diagnostic station before proceeding with diagnosis.
  11. Reconnect the EVAP purge pipe to the EVAP canister purge valve. Install the fuel tank cap adapter. Connect the EVAP pressure/purge diagnostic station to the fuel tank cap adapter. Turn ON the ignition, with the engine OFF. Use a scan tool in order to seal the EVAP system. Using the EVAP diagnostic station, attempt to pressurize the EVAP system to the specified value. Rotate the EVAP diagnostic station rotary switch to the OFF/HOLD position. Were you able to obtain and hold 5 in. H2O for 1 minute? If yes, go to next step. If no, go to step  13 .
  12. Compare the EVAP diagnostic station pressure gage value to the scan tool Fuel Tank Pressure (FTP) sensor value. Is the EVAP pressure/purge diagnostic station gage value near the FTP sensor scan tool value? If yes, go to step  14 . If no, go to step  29 .
    13. NOTE: It may be necessary to partially lower the fuel tank to inspect components located in the upper portion of the tank.
  13. With the pressure/purge diagnostic station, continuously attempt to 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 valves, and fuel tank.

    Did you find and repair the condition? If yes, go to step  31 . If no, see DIAGNOSTIC AIDS  .

  14. Observe the EVAP diagnostic station pressure gage. Disconnect the EVAP purge pipe from the EVAP canister. Does the EVAP pressure/purge diagnostic station gage decrease to near 0 in. H2O? If yes, go to step  24 . If no, go to next step.
  15. Observe the pressure gage on the EVAP diagnostic station. Disconnect the EVAP vapor pipe from the EVAP canister. Does the EVAP pressure/purge diagnostic station gage decrease to near 0 in. H2O? If yes, go to step  28 . If no, go to step  25 .
  16. Test the control circuit of the EVAP purge valve for an open or short to voltage. Did you find and correct the condition? If yes, go to step  31 . If no, go to step  20 .
  17. Test the control circuit of the EVAP vent valve for an open or short to voltage. Did you find and correct the condition? If yes, go to step  31 . If no, go to step  20 .
  18. Test for poor connections at the harness connector of the EVAP purge valve. Did you find and correct the condition? If yes, go to step  31 . If no, go to step  26 .
  19. Test for poor connections at the harness connector of the EVAP vent valve. Did you find and correct the condition? If yes, go to step  31 . If no, go to step  27 .
  20. Test for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step  31 . If no, go to step  30 .
  21. 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, to step  31 . If no, go to step  26 .
  22. Repair the ignition voltage circuit of the EVAP purge valve for an open or short to ground. Replace the fuse if necessary. After repair, go to step  31 .
  23. Repair the ignition voltage circuit of the EVAP vent valve for an open or short to ground. Replace the fuse if necessary. After repair, go to step  31 .
  24. Repair the restriction in the EVAP purge pipe. See EVAPORATIVE EMISSION SYSTEM CLEANING in REMOVAL, OVERHAUL & INSTALLATION. After repairs, go to step  31 .
  25. Repair the restriction in the EVAP vapor pipe. After repairs, go to step  31 .
    26. NOTE: Check for carbon release into the EVAP system. If carbon is present, see EVAPORATIVE EMISSION SYSTEM CLEANING in REMOVAL, OVERHAUL & INSTALLATION.
  26. Replace the EVAP canister purge valve. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  31 .
  27. Replace the EVAP vent valve. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  31 .
  28. Replace the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  31 .
  29. Replace the FTP sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  31 .
  30. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  31. Turn ON the ignition, with the engine OFF. Command the EVAP vent valve ON with a scan tool. Pressurize the EVAP system to 5 in. H2O with the EVAP pressure/purge diagnostic station. Place the control knob on the EVAP pressure/purge diagnostic station to the OFF/HOLD position. Monitor the EVAP system pressure on the EVAP pressure/purge diagnostic station for 5 minutes. Does the EVAP system pressure remain constant? If yes, go to next step. If no, go to step  4 .
  32. 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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