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Home >> Buick >> 2015 >> Regal GS, AWD >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls And Fuel - 2.0L (LTG) - DTC P0335 To DTC P2635 And Diagnostic Information And Procedures >> Diagnostic Information and Procedures >> DTC P0420: Catalyst System Low Efficiency >> Circuit/System Verification

Circuit/System Verification

  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. Verify the Catalyst Monitor Test Result parameter displays Passed when performing the steps listed below:
    1. Monitor the scan tool Catalyst Monitor Test State parameter. When the parameter indicates Active, the Catalyst Monitor Test is running.
      2. NOTE:

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

    2. Continue to monitor the parameter. When the parameter indicates Inactive, the Catalyst Monitor Test has completed.
    3. Verify the scan tool Catalyst Monitor Test Result displays Passed.
    • If No Result is displayed 

      Repeat steps 3-5 until the Test Result parameter indicates Passed or Failed

    • If Failed is displayed 

      Refer to Circuit/System Testing

    • If Passed is displayed 
  6. All OK.
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