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DTC P0420 - CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD Hyundai Sonata III рестайлинг

Testing & Diagnostics
  1. Install scan tool. Start engine and check if DTC P0420 is present. If DTC is present, go to next step. If DTC is not present, problem is intermittent. See INTERMITTENTS in «TESTS W/O CODES»(ref-16659) article.
  2. Check for exhaust leak before and after catalytic converter, especially near HO2S. Repair as necessary. If leaks are not present, go to next step.
  3. Check rear HO2S. For diagnosis, see DTC P0130/P0136. If HO2S sensor is okay, replace catalytic converter. Clear DTC. See CLEARING CODES under Self Diagnostic System section. Retest system. If DTC resets, replace ECM.

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