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Home >> Buick >> 2002 >> Century Custom >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 3.1L Engine >> Inspection/Maintenance Procedures >> Inspection/Maintenance Complete 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, go to INSPECTION/MAINTENANCE SYSTEM CHECK .
    NOTE: Whenever ignition is turned ON, ignition positive voltage is supplied to HO2S heaters. After verifying the enable criteria, turn off the ignition for about 5 minutes to allow the sensors to cool before continuing with the test. Once engine is started, DO NOT turn engine off for the remaining portion of the set procedure.
  2. Preprogram the scan tool with the vehicle information before ignition is turned ON. Ensure that vehicle is within the Conditions for Running Test (Cold Start). See CONDITIONS FOR RUNNING TEST (COLD START) . Turn off all accessories, e.g., A/C, blower fan, etc. Set vehicle parking brake. Verify that transmission is in Park (A/T) or Neutral (M/T). Start and allow engine to idle for 2 minutes. When complete, go to next step.
    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.
  3. In order for the next group of tests to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 55 MPH. Maintain this speed without changing throttle position for 8-10 minutes until engine reaches operating temperature. Continue operating under these conditions for additional 6 minutes. When complete, go to next step.
  4. In order for this test to run, the vehicle must operate in the following conditions: The vehicle speed is reduced to 45 MPH with this speed maintained for one additional minute. Four decelerations of 25 seconds each from 45 MPH while the following criteria is maintained: The throttle is closed, no brake application on either manual or automatic transmissions, no clutch actuation (M/T), no manual downshifts, and vehicle speed remains greater than 25 MPH. After each deceleration period, vehicle is returned to 45 MPH under part throttle acceleration and speed is maintained for 15 seconds. When complete, go to next step.
  5. In order for the next group of tests to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 45-55 MPH and maintain this speed for 2 minutes, then decelerate to 0 MPH. With engine idling for 2 minutes, the following criteria should be maintained: Service brake depressed, transmission in Drive (A/T) or Neutral (M/T) with clutch pedal depressed. When complete, go to next step.
  6. With a scan tool, observe the I/M system Status display. Did all of the I/M system Status indicators update to YES? If yes, go to next step. If no, go to the I/M System Set Procedure for the indicated systems.
  7. Using scan tool, observe emission related DTC portion of I/M system status display. Does the scan tool indicate any emission related DTCs set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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