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OBD II P0420, Catalyst System Efficiency Below Threshold. In some cases, there may be some performance problems noticed by the driver such as a lack of power from a restricted and/or damaged Catalytic Converter.

Common Problems That Trigger the P0420 Code

  • Inefficient Catalytic Converter(s)
  • Defective Front or Rear Oxygen Sensor(s)
  • Misfiring engines

Common Misdiagnoses

  • Oxygen Sensors good-day ! hope this helps !
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13y ago

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