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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 405 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0449: EVAP Vent Valve Performance >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Cadillac Seville and 2003 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
  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 ignition on, with engine off. Command the EVAP vent solenoid on and off with a scan tool. 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. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition cycle? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  4. Turn ignition off. Disconnect the EVAP vent valve. Turn ignition on, with engine off. Probe the EVAP vent valve ignition 1 voltage circuit at the EVAP vent valve harness connector with a test light connected to a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  11.
  5. Connect a test light between the control circuit and ignition 1voltage circuit of the EVAP vent valve at the EVAP vent valve harness connector. Command the EVAP vent solenoid on and off with a scan tool. Does the test light turn on and off with each command? If yes, go to step  9. If no, go to next step.
  6. Does the test light remain illuminated with each command? If yes, go to step  8. If no, go to next step.
  7. Test the EVAP vent valve control circuit for a short to voltage or an open. Did you find and correct the condition? If yes, go to step  14. If no, go to step  10.
  8. Test the EVAP vent valve control circuit for a short to ground. Did you find and correct the condition? If yes, go to step  14. If no, go to step  10.
  9. Test for an intermittent and/or poor connections at the EVAP vent valve. Did you find and correct the condition? If yes, go to step  14. If no, go to step  12.
  10. Test for an intermittent and/or poor connections at the PCM. Did you find and correct the condition? If yes, go to step  14. If no, go to step  13.
  11. Repair the open or short to ground in the ignition 1 voltage circuit. Did you complete the repair? If yes, go to step  14.
  12. Replace the EVAP vent valve. See EVAP CANISTER VENT VALVE under MOTORS & SOLENOIDS in REMOVAL & INSTALLATION - DEVILLE & SEVILLE article. Did you complete the replacement? If yes, go to step  14.
  13. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - DEVILLE & SEVILLE article. Did you complete the replacement? If yes, go to next step.
  14. Clear the DTCs with a scan tool. Turn off the ignition for 30 seconds. Start the engine and operate vehicle within the Conditions For Running DTC. You may also operate vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition cycle? If yes, go to step  2. If no, go to next step.
  15. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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