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Home >> GMC >> 2003 >> Envoy RWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Self-Diagnostics - 4.2L >> Drive Cycles >> Inspection/Maintenance Catalyst System Set Procedure >> Diagnostic Procedures
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Diagnostic Procedures

  1. Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, see INSPECTION/MAINTENANCE SYSTEM CHECK .
    2. WARNING: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
  2. Ensure the vehicle is within the CONDITIONS FOR RUNNING . Turn OFF all of the accessories (e.g., A/C, blower fan, etc.). Start the engine and allow the engine to idle. For this test to run, the vehicle must operate in the following conditions:
    • Acceleration at part throttle to 55 MPH with this speed maintained for 5 minutes.
    • Deceleration to zero MPH.
    • Engine idling for 2 minutes while the following criteria is maintained:
      1. Service brake depressed.
      2. Automatic transmission in Drive.
      3. Manual transmission in Neutral with the clutch pedal depressed.

    With scan tool, observe the I/M System Status display. Did the Catalyst System Status update to YES? If yes, go to step  5. If no, go to next step.

  3. With scan tool, observe the DTC Information. Does scan tool indicate any failed DTCs? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  4. To determine which DTCs are required to run in order to complete this test, see INSPECTION/MAINTENANCE SYSTEM DTCS  table. With scan tool, observe the Not Ran Since Code Cleared display. Determine which of the DTCs required for a YES status has not run. Enter the DTC number in the Specific DTC menu of scan tool. Operate the vehicle within the Conditions For Running DTC, located in appropriate DTC test. Repeat the procedure until scan tool indicates the diagnostic test has run. Repeat steps 4-6 for any additional required DTCs that have not run. With scan tool, observe the I/M System Status display. Did the Catalyst System Status update to YES? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  5. With scan tool, observe the Emission Related DTC portion of the I/M System Status display. Does scan tool indicate any Emission Related DTCs set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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