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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 100 (Engine Control System Self-Diagnostics - 3.8L) >> Diagnostic Tests >> DTC P0449: EVAP Vent Solenoid Valve Control Circuit >> Diagnostic Procedures

Diagnostic Procedures

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  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. Turn ignition on, engine off. Using scan tool, command EVAP vent valve on and off. Does the EVAP vent valve turn on and off when commanded? If yes, go to next step. If no, go to step  4.
  3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within Conditions for Running DTC or as close to FREEZE FRAME/FAILURE RECORDS data as possible. Does this 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 EVAP vent valve. Turn ignition on, engine off. Probe the ignition voltage circuit of the EVAP vent valve at the EVAP vent valve harness 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  11.
  5. Connect a test lamp between the control circuit of the EVAP vent valve and ignition voltage circuit of the EVAP vent valve at the EVAP vent valve harness 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 solenoid 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 control circuit of the EVAP vent valve 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. 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  14. If no, go to step  12.
  10. Inspect for poor connections at the harness connector of PCM. Did you find and correct the condition? If yes, go to step  14. If no, go to step  13.
  11. Repair the ignition voltage circuit of the EVAP vent valve for an open or a short to ground. After repairs, go to step  14.
  12. Replace EVAP vent valve. After repairs, go to step  14.
  13. Replace PCM. Program replacement PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  14. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within Conditions for Running DTC. Does DTC run and pass? If yes, go to next step. If no, go to step  2.
  15. 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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