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Home >> Buick >> 2017 >> Verano Base, Gas >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls And Fuel - 2.4L (Lea) - DTC P0335 To DTC P2635 And Diagnostic Information And Procedures >> Diagnostic Information and Procedures >> DTC P0420: Catalyst System Low Efficiency >> Circuit/System Testing

Circuit/System Testing

  1. Verify the conditions listed below do not exist with the catalytic converter:
    • Dents
    • Severe discoloration caused by excessive temperatures
    • Road damage
    • Internal rattles caused by damaged catalyst substrate
    • Restrictions
    • If a condition is found 

      Replace the catalytic converter.

    • If no condition is found 
  2. Verify the conditions listed below do not exist with the exhaust system:
    • Leaks
    • Physical damage
    • Loose or missing hardware
    • If a condition is found 

      Repair or replace the component as necessary.

    • If no condition is found 
  3. Verify the conditions listed below do not exist with the B52B Heated Oxygen Sensor 2:
    • Incorrect torque
    • Damage
    • If a condition is found 

      Replace the B52B Heated Oxygen Sensor 2 or repair the condition as necessary.

    • If no condition is found 
  4. Test or replace the catalytic converter.
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