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Home >> Hyundai >> 2017 >> Sonata Base >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 39 (Engine Control System Diagnosis - 1.6L (2 Of 3) (Except HEV)) >> DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1) >> System Inspection

System Inspection

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  1. Visual check
    • Check air leakage at junction of HO2S or Catalyst converter.
    • Check looseness, poor connection, or damage.
  2. Is there something wrong?

    YES 

    NO