Question

2000 Chevrolet Blazer Vortec 4.3L with engine code P0420 Replaced Cat Converter and Oxygen Sensors and I still have the same code.

Answer 1

Did you use a factory Catalytic converter? and are you using high-octane gas? I have seen some new aftermarket Catalytic converters not working to factory standards.

P0420 Chevrolet Code - Catalyst System Low Efficiency Bank 1
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