2002 Buick Century LimitedFACTORY OEM SERVICE PROCEDURE

Diagnostic Procedures

  1. Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, go to INSPECTION/MAINTENANCE SYSTEM CHECK .
    WARNING: Road test 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 Test. See CONDITIONS FOR RUNNING TEST . Turn off all of the accessories, e.g., A/C, blower fan, etc. Start and idle the engine. Important: In order for this test to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 55 MPH. Maintain this speed without changing the throttle position for 5. Decelerate to 0 MPH. Operate engine at idle for 2 minutes while the following criteria is maintained: Service brake depressed, and transmission in Drive (A/T). Using 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. Using scan tool, observe DTC Information. Does the scan tool indicate any failed DTCs? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
    NOTE: Refer to INSPECTION/MAINTENANCE SYSTEM DTCS  to determine which DTCs are required to run in order to complete this test.
  4. Using scan tool, observe the NOT RAN SINCE CODE CLEARED display. Determine which of the DTCs required for a YES status has not run. Enter DTC in Specific DTC menu on scan tool. Operate vehicle within Conditions for Running Test. See CONDITIONS FOR RUNNING TEST . Repeat procedure until scan tool indicates the diagnostic test has run. Repeat this step for any additional required DTCs that have not run. Using scan tool, observe I/M system Status display. If yes, go next step. If no, see DIAGNOSTIC AIDS .
  5. Using scan tool, observe emission related DTC portion of I/M system Status display. Does scan tool indicate any emission related DTCs? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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