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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 335 (Engine Controls - Self-Diagnostics - 3.0L) >> Diagnostic Tests >> DTC P0448: Control System - Vent Shorted >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Saturn Vue. 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, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS .
  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 solenoid when the solenoid is commanded ON and OFF? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records for this DTC with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions for Running the DTC. See 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? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  4. Turn ignition off. Disconnect the EVAP vent solenoid. Turn ignition on, with engine off. Measure the voltage on the EVAP vent solenoid control circuit. Is the voltage greater than 4.6 volts? If yes, go to next step. If no, go to step  6.
  5. Test the control circuit of the EVAP vent solenoid for a short to voltage. Did you find and correct the condition? If yes, go to step  10. If no, go to step  7.
  6. Test for an intermittent and for a poor connection at the EVAP vent solenoid. Did you find and correct the condition? If yes, go to step  10. If no, go to step  8.
  7. Test for an intermittent and for a poor connection at the control module. Did you find and correct the condition? If yes, go to step  10. If no, go to step  9.
  8. Replace EVAP vent solenoid. After replacing solenoid, go to step  10.
  9. Replace ECM. Perform ECM relearn procedures. See ENGINE CONTROL MODULE  under PROGRAMMING. After replacing ECM, go to next step.
  10. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions for Running the DTC. See 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? If yes, go to step  2. If no, go to next step.
  11. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are displayed, system is okay.
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