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Home >> Buick >> 2015 >> Regal GS, AWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 15 (Engine Controls And Fuel - 2.4L - DTC P0114 To DTC P0604) >> Diagnostic Information and Procedures >> DTC P0420: Catalyst System Low Efficiency (LEA) >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different variant/trim than selected.
  1. Ignition On.
  2. Verify there are no other DTCs set.
    • If no other DTCs are set 
  3. Operate the vehicle within the Conditions for Running the DTC.
  4. Verify the scan tool Catalyst Monitor Not At Idle Test Conditions Met parameter changes to Yes.
    • If Yes is not displayed 

      Refer to step 3.

    • If Yes is displayed 
  5. When the conditions are safe, stop and idle the vehicle in gear if equipped with automatic transmission or neutral if equipped with manual transmission.
  6. Verify the Catalyst Monitor Test Result parameter displays Passed when performing the steps listed below:
    1. Apply the service brake.
    2. Monitor the scan tool Catalyst Monitor Test State parameter. When the parameter indicates Active, the Catalyst Monitor Test is running.
      3. NOTE:

      When the test has completed, the Catalyst Monitor Test Counter parameter will increment by one and the Catalyst Monitor Test Result parameter will indicate Passed, Failed or No Result.

    3. Continue to monitor the parameter. When the parameter indicates Inactive, the Catalyst Monitor Test has completed.
    • If No Result is displayed 

      Repeat steps 3-6 until the Test Result parameter indicates Passed or Failed

    • If Failed is displayed 

      Refer to Circuit /System Testing

    • If Passed is displayed 
  7. All OK.
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