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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 89 (Engine Controls And Fuel - 3.6L (LF4 LGX) - DTC P0121 LF4 To DTC P0685 LF4) >> Diagnostic Information and Procedures >> DTC P0420 or P0430: Catalyst System >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2016 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition ON.
  2. Verify there are no other DTCs set.
    • If a DTC is not 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. Monitor the scan tool Catalyst Monitor Test State parameter. When the parameter indicates Active, the Catalyst Monitor Test is running.
    6. NOTE:

    When the test has completed, the Catalyst Monitor Test Counter Bank 1 and Bank 2 parameters will increment by one and the Catalyst Monitor Test Result Bank 1 and Bank 2 parameters will indicate Passed, Failed or No Decision.

  6. Continue to monitor the parameter. When the parameter indicates Inactive, the Catalyst Monitor Test has completed.
    • If the Catalyst Monitor Test Result Bank 1 or Bank 2 parameter indicates No Decision 

      Repeat steps 3-6 until the Test Result parameters indicate Passed or Failed

    • If the Catalyst Monitor Test Result Bank 1 or Bank 2 parameter indicates Failed 

      Refer to Circuit /System Testing

    • If the Catalyst Monitor Test Result Bank 1 and Bank 2 parameters indicate Pass 
  7. All OK.
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