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Home >> Pontiac >> 2002 >> Aztek FWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0449: 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. Turn ON the ignition, with the engine OFF. With the scan tool, command the EVAP vent valve ON and OFF. Do you hear or feel a click from the EVAP vent valve when the valve is commanded ON and OFF? If yes, go to next step. If no, go to step  4.
  3. Review the Freeze Frame/Failure Records data for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC or as close to the Freeze Frame/Failure Records data that you observe. Does this DTC fail this ignition cycle? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  4. Raise the vehicle. Disconnect the fuel tank wiring harness at the body pass-through connector. Probe the ignition voltage circuit of the EVAP vent valve at the body pass-through connector with a test lamp connected to a good ground. Does the test lamp illuminate? If yes, go to next step. If no, go to step  13.
  5. Connect a test lamp between the control circuit of the EVAP vent valve and the ignition voltage circuit of the EVAP vent valve at the body pass-through connector. With a scan tool, command the EVAP vent valve ON and OFF. Does the test lamp turn ON and OFF with each command? If yes, go to step  9. If no, go to next step.
  6. Does the test lamp remain illuminated with each command? If yes, go to step  8. If no, go to next step.
  7. Test the control circuit of the EVAP vent valve for a short to voltage or an open. Did you find and correct the condition? If yes, go to step  16. If no, go to step  12.
  8. Test the control circuit of the EVAP vent valve for a short to ground. Did you find and correct the condition? If yes, go to step  16. If no, go to step  12.
  9. Inspect for poor connections at the body pass-through connector. Did you find and correct the condition? If yes, go to step  16. If no, go to next step.
  10. Remove the fuel tank. Disconnect the EVAP vent valve electrical connector. Test the EVAP vent valve jumper harness circuits for an open or short to ground. Did you find and correct the condition? If yes, go to step  16. If no, go to next step.
  11. Inspect for poor connections at the harness connector of the EVAP vent valve. Did you find and correct the condition? If yes, go to step  16. If no, go to step  14.
  12. Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step  16. If no, go to step  15.
  13. Repair the ignition voltage circuit of the EVAP vent valve for an open or a short to ground. After repairs, go to step  16.
  14. Replace the EVAP vent valve. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  16.
  15. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  16. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  17. 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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