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Home › Pontiac › 2002 › Firebird Formula, Automatic › Repair and Diagnosis › Engine Performance › System › Engine Control System Self-Diagnostics - 5.7L › Diagnostic Tests › DTC P0446: EVAP Vent Valve Performance › Diagnostic Procedures

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, P0452 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. With a scan tool, review and record the Freeze Frame/Failure Records data. With a scan tool, clear the DTC codes. Perform the Service Bay Test. See INSPECTION/MAINTENANCE EVAPORATIVE EMISSION SYSTEM SET PROCEDURE  under SELF-DIAGNOSTIC SYSTEM. Does the scan tool indicate that the Service Bay Test has passed? If yes, see DIAGNOSTIC AIDS . If no, go to next step.
  5. 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.
    6. NOTE: Always zero the EVAP pressure and vacuum (in. H2O) gauges on the EVAP pressure/purge diagnostic station before proceeding with diagnosis.
  6. 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. Disconnect the EVAP vent hose from the EVAP vent valve. Does the scan tool indicate that the FTP decreased? If yes, go to step  10. If no, go to next step.
  7. Disconnect the EVAP vapor pipe from the EVAP canister. Does the scan tool indicate that the FTP decreased? If yes, go to step  13. If no, go to step  11.
  8. With a scan tool, observe the fuel tank pressure 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 fuel tank pressure 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. After repairs, go to step  14.
  11. Replace the EVAP canister. After repairs, go to step  14.
  12. Replace the FTP sensor. After repairs, go to step  14.
  13. Repair for a blockage in the EVAP vent hose. After repairs, go to next step.
  14. Reconnect all of the EVAP hardware that was previously disconnected. Perform the Service Bay Test. See INSPECTION/MAINTENANCE EVAPORATIVE EMISSION SYSTEM SET PROCEDURE  under SELF-DIAGNOSTIC SYSTEM. Does the scan tool indicate that the Service Bay Test has passed? 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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