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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 377 (Engine Controls - Self-Diagnostics - 4.3L) >> Diagnostic Tests >> DTC P0446: EVAP Vent Valve Performance >> Diagnostic Procedures

Diagnostic Procedures

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  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. Inspect the EVAP system for a damaged EVAP vent solenoid, pinched EVAP vent hose, or damaged EVAP canister. Did you find and correct the condition? If yes, go to step  12. If no, go to next step.
  3. Turn ignition off. Disconnect the purge line from the EVAP purge solenoid. Turn ignition on, with engine off. Is the fuel tank pressure sensor parameter within -1 to 1 in. H2O? If yes, go to next step. If no, go to step  8.
    4. NOTE: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
  4. Turn ignition off. Connect the EVAP purge pipe. Connect the Evaporative Emissions System Tester (J-41413-200) power supply clips to a known good 12-volt source. Install Fuel Tank Cap Adapter (J-41415-40) to the fuel fill pipe. Connect the fuel fill cap to the Fuel Tank Cap Adapter. Connect the Evaporative Emissions System Tester nitrogen/smoke supply hose to the Fuel Tank Cap Adapter. Turn ignition on, with engine off Command the EVAP vent solenoid closed with a scan tool. Turn the nitrogen/smoke valve on the Evaporative Emissions System Tester control panel to NITROGEN. Use the remote switch to pressurize the EVAP system to 5 in. H2O. Observe the fuel tank pressure sensor in. H2O with a scan tool. Command the EVAP vent solenoid open with a scan tool. Is the fuel tank pressure sensor parameter less than 1 in. H2O? If yes, go to DIAGNOSTIC AIDS . If no, go to next step.
  5. Disconnect the EVAP vent hose from the EVAP vent solenoid. Is the fuel tank pressure sensor parameter less than 1 in. H2O? If yes, go to step  10. If no, go to next step.
  6. Disconnect the EVAP vent hose from the EVAP canister. Is the fuel tank pressure sensor parameter less than 1 in. H2O? If yes, go to next step. If no, go to step  11.
  7. Repair the pinched or restricted EVAP vent hose. After repairs, go to step  12.
  8. Test for poor connections at the harness connector of the FTP sensor. Did you find and correct the condition? If yes, go to step  12. If no, go to next step.
  9. Replace FTP sensor. After replacing sensor, go to step  12.
  10. Replace EVAP vent valve. After repairs, go to step  12.
  11. Replace EVAP canister. See appropriate REMOVAL & INSTALLATION article. After repairs, go to next step.
  12. Turn ignition off. Disconnect the purge line from the EVAP purge solenoid. Refer to Evaporative Emission (EVAP) Canister Purge Valve Replacement. Turn ignition on, with engine off. Is the fuel tank pressure sensor parameter within -1 to 1 in. H2O? If yes, go to next step. If no, go to step  2.
    13. NOTE: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
  13. Turn ignition off. Reconnect all disconnected components. Connect the Evaporative Emissions System Tester to the fuel fill pipe. Turn ignition on, with engine off. Command the EVAP vent solenoid closed with a scan tool. Turn the nitrogen/smoke valve on the Evaporative Emissions System Tester control panel to NITROGEN. Use the remote switch to pressurize the EVAP system to 5 in. H2O. Observe the fuel tank pressure sensor in. H2O with a scan tool. Command the EVAP vent solenoid open with a scan tool. Is the fuel tank pressure sensor parameter less than 1 in. H2O? If yes, go to next step. If no, go to step  2.
  14. 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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