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Home >> Buick >> 2016 >> Cascada Base >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls And Fuel - 1.6L (LWC) - DTC P0300 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(s):
    • 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(s).

      • 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 warm up three-way catalytic converter and the exhaust front pipe.
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