How to repair catalyst system efficiency below threshold bank 1 & 2?

Question

what causes catalyst system efficiency below threshold bank 1 & 2 and how to repair

Answer 1

P0420 Catalytic below threshold Bank 1

P0430 Catalytic below threshold Bank 2

This all depends, the most common is the function of the 02 sensor, The CK ENG LT program was built on the 02 sensor, which is the main management. Some of the causes for a catalytic to go below the threshold is a degraded catalytic convertor,

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Here is a 02 sensor that set a P0420, A good catalytic converter downstream   02 sensor voltage would be above 650 mv.  here it goes below, this is what a catalytic below the threshold

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Here a faulty rear 02 sensor set a catalytic below threshold code condition