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p0420 Catalyst System Efficiency Below Threshold (Bank 1)

NaturallySmashed

NaturallySmashed

New member
Just figured I'd make a post to see what you guys think.. I believe this code is usually for a bad catalytic converter.. I have no way to test it. Should I just change the o2 sensor first? Also, would that be the o2 after the cat?
 


The code tells you that the difference in readings before and after the cat do not have the necessary amount of change as expected by the pcm with a good functioning cat.

The sensors are seemingly reading ok. There shouldn't be a need to change a sensor.
 
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