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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 P0446: EVAP Vent System Performance >> 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. Did DTC P0443, P0449, P0452, or P0453 set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Inspect EVAP system for a damaged EVAP vent valve and a pinched EVAP fresh air vent hose. Did you find and correct the condition? If yes, go to step  15. 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. Disconnect purge line from EVAP purge valve. Turn ignition on, engine off. Using scan tool, observe FTP parameter. Does the scan tool indicate FTP near zero in. H2O? If yes, go to next step. If no, go to step  9.
    6. NOTE: Always zero EVAP pressure and vacuum (in. H2O) gauges on EVAP Pressure and Purge Station (J 41413) before proceeding with diagnosis.
  6. 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. Does the scan tool indicate FTP near zero in. H2O? If yes, see DIAGNOSTIC AIDS . If no, go to next step.
  7. Disconnect EVAP canister vent hose from EVAP canister vent valve. Does the scan tool indicate fuel tank pressure near zero in. H2O? If yes, go to step  11. If no, go to next step.
  8. Disconnect EVAP vent hose from EVAP canister. Does the scan tool indicate FTP near zero in. H2O? If yes, go to step  14. If no, go to step  12.
  9. Using scan tool, observe FTP sensor voltage. Is the FTP sensor voltage more than 4.3 volts? If yes, see DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE . If no, go to next step.
  10. Test for poor connections at the harness connector of the FTP sensor. Did you find and correct the condition? If yes, go to step  15. If no, go to step  13.
  11. Replace EVAP canister vent valve. After repairs, go to step  15.
  12. Replace EVAP canister. After repairs, go to step  15.
  13. Replace FTP sensor. After repairs, go to step  15.
  14. Repair blockage in EVAP vent hose. After repairs, go to next step.
  15. 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.
  16. 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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