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Home >> Pontiac >> 2002 >> Aztek AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0446: EVAP Vent Valve Performance >> 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. Did DTC P0443, P0449 or P0453 set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Inspect the EVAP system for the following conditions:
    • A damaged EVAP vent valve.
    • A pinched EVAP vent hose.

    Did you find and correct the condition? If yes, go to step  14. If no, go to next step.

  4. Disconnect the purge line from the EVAP purge valve. Turn ON the ignition, with the engine OFF. With a scan tool, observe the FTP parameter. Does the scan tool indicate FTP near 0 in. H2O? If yes, go to next step. If no, go to step  8.
    5. NOTE: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
  5. Turn OFF the ignition. Reconnect all previously disconnected hardware. Install the J 41415-40 Fuel Fill Cap Adapter. Connect the J 41413 EVAP Pressure/Purge Diagnostic Station and the vehicle fuel fill cap to the J 41415-40. Turn ON the ignition, with the engine OFF. With a scan tool, seal the EVAP system. With the J 41413, pressurize the EVAP system to 5 in. H2O. Rotate the J 41413 rotary switch to the OFF/HOLD position. Command the EVAP canister vent valve OFF with a scan tool. Does the scan tool indicate FTP near 0 in.H2O? If yes, see DIAGNOSTIC AIDS . If no, go to next step.
  6. Disconnect the EVAP vent pipe from the EVAP canister. Does the scan tool indicate fuel tank pressure at -0.5-0.5 in. H2O? If yes, go to step  10. If no, go to next step.
  7. Disconnect the EVAP vent pipe from the EVAP canister. Does the scan tool indicate FTP near 0 in. H2O? If yes, go to step  13. If no, go to step  11.
  8. With a scan tool, observe the FTP sensor voltage. 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 next step.
  9. Test for poor connections at the harness connector of the FTP sensor. Did you find and correct the condition? If yes, go to step  14. If no, go to step  12.
  10. Replace the EVAP vent valve. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  14.
  11. Replace the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  14.
  12. Replace the FTP sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  14.
  13. Repair for a blockage in the EVAP vent hose. After repairs, go to next step.
    14. NOTE: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
  14. 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. Turn the J 41413 rotary valve to the OFF/HOLD position. Monitor the J 41413 pressure gauge. Command the EVAP canister vent valve OFF with a scan tool. Does the EVAP system pressure decrease? If yes, go to next step. If no, go to step  3.
  15. 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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