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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 EVAP 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 .
  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 engine. Important: In order for this test to run, vehicle must operate in the following conditions: Operate engine until it reaches operating temperature of at least 158°F (70°C). This may be up to 8-10 minutes depending on the start-up coolant temperature. Accelerate at part throttle to 30-50 MPH. Operate vehicle for 20 minutes at speeds of 30-50 MPH or more. Operate vehicle for 3 minutes at 30-50 MPH with throttle position steady. Using scan tool, observe the I/M system Status display. Did the EVAP system Status update to YES? If yes, go to step  5. If no, go to next step.
  3. Using a scan tool, select Special Functions. Determine if the vehicle is equipped with a Service Bay Test for the EVAP System. Is the vehicle equipped with EVAP Service Bay Test? If yes, go to step  8. If no, go to next step.
  4. Observe the scan tool Service Bay Test for an indication of why the test did not pass, e.g., failed DTC, test aborted, etc. Refer to the appropriate service information for diagnosis and repair of the condition as necessary. After repairs, go to INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE .
    NOTE: Once engine is started, DO NOT turn engine off for the remainder of the procedure until test is complete
  5. Ensure that 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. Accelerate at part throttle to 45 MPH and maintained speed until engine reaches operating temperature. This may be up to 8-10 minutes depending on the start-up coolant temperature. Continue the operating conditions for an additional 3 minutes after the engine reaches operating temperature, or until the I/M System Status indicator updates to YES. Decelerate to 0 MPH. Operate engine at idle 2 minutes. Did the EVAP System Status update to YES? If yes, go to step  8. If no, go to next step.
  6. With a scan tool, observe the DTC Information. Does the scan tool indicate any failed DTCs? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  7. Refer to the Inspection/Maintenance (I/M) System DTCs to determine which DTCs are required to run in order to complete this test. See INSPECTION/MAINTENANCE SYSTEM DTCS . With a 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 the scan tool. Operate the vehicle within the Conditions for Running Test. See CONDITIONS FOR RUNNING TEST . Repeat the procedure until the scan tool indicates the diagnostic test has run. Repeat  4 -  6 for any additional required DTCs that have not run. With a scan tool, observe the I/M System Status display. Did the EVAP System Status update to YES? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  8. With a scan tool, observe the Emission Related DTC portion of the I/M System Status display. Does the scan tool indicate any Emission Related DTCs set? If yes, DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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