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Home >> Buick >> 2001 >> Regal LS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 3.8L >> Diagnostic Tests >> DTC P0446: EVAP Vent System Performance >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
  2. If DTCs P0443, P0449, P0452, or P0453 are set, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If DTCs P0443, P0449, P0452, or P0453 are not set, go to next step.
  3. Inspect EVAP system for a damaged EVAP vent valve and a pinched EVAP fresh air vent hose. If problem was found, repair as necessary. After repairs, go to step  14. If problem was not found, go to next step.
  4. Disconnect purge line from EVAP purge valve. Turn ignition on, engine off. Using scan tool, observe FTP parameter. If scan tool indicates FTP about zero in. H2O, go to next step. If scan tool does not indicate about zero in. H2O, go to step  8.
    5. NOTE: Always zero EVAP pressure and vacuum (in. H2O) gauges on EVAP Pressure and Purge Station (J 41413) before proceeding with diagnosis.
  5. Turn ignition off. Reconnect all previously disconnected components. Install Fuel Tank Cap Adapter (J 41415-40). Connect EVAP pressure and purge station 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 EVAP system to 5 in. H2O. Rotate EVAP pressure and purge station rotary switch to OFF/HOLD position. Using scan tool, command EVAP canister vent valve off. If scan tool indicates FTP about zero in. H2O, see DIAGNOSTIC AIDS . If scan tool does not indicate FTP about zero in. H2O, go to next step.
  6. Disconnect EVAP canister vent hose from EVAP canister vent valve. If scan tool indicates fuel tank pressure about zero in. H2O, go to step  10. If scan tool does not indicate fuel tank pressure about zero in. H2O, go to next step.
  7. Disconnect EVAP vent hose from EVAP canister. If scan tool indicates FTP about zero in. H2O, go to step  13. If scan tool does not indicate FTP about zero in. H2O, go to step  11.
  8. Using scan tool, observe FTP sensor voltage. If FTP sensor voltage is more than 4.3 volts, see DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE . If FTP sensor voltage is not more than 4.3 volts, go to next step.
  9. Check FTP sensor connector for poor connections. If problem was found, repair as necessary. After repairs, go to step  14. If problem was not found, go to step  12.
  10. Replace EVAP canister vent valve. After repairs, go to step  14.
  11. Replace EVAP canister. After repairs, go to step  14.
  12. Replace FTP sensor. After repairs, go to step  14.
  13. Repair blockage in EVAP vent hose. After repairs, go to next step.
    14. NOTE: DO NOT exceed specified value in this step. Exceeding specified value may produce incorrect test results.
  14. Turn ignition on, engine off. Using scan tool, command EVAP canister vent valve on. Using EVAP pressure and purge station, pressurize EVAP system to 5 in. H2O. Turn EVAP pressure and purge station rotary valve to OFF/HOLD position. Monitor EVAP pressure and purge station pressure gauge. Using scan tool, command EVAP canister vent valve off. If EVAP system pressure decreases, go to next step. If EVAP system pressure does not decrease, go to step  3.
  15. Using scan tool, observe stored information. If scan tool displays any DTCs that have not been diagnosed, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If scan tool does not display any DTCs, system is okay.
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