P0420 replaced O2 bank 1 came back on now what? - Ford Mustang Forum
 
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post #1 of 5 (permalink) Old 09-27-2019 Thread Starter
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P0420 replaced O2 bank 1 came back on now what?

I replaced O2 sensor 1 bank 1 after about 100 miles check engine light was back with exact code. Currently I am running a Ford Racing dual exhaust cat back. Driver's side is loose at the brackets in the rear. It rattles a little. Could that cause a problem with O2 sensors? What do I need to do next? I've heard of actually checking the cat, looking for an exhaust leak, and possibly cleaning the MAF (which is on a Ford Racing intake)? Anybody have some suggestions?

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post #2 of 5 (permalink) Old 09-27-2019
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In short, yes, an exhaust leak could trigger that code......


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post #3 of 5 (permalink) Old 09-27-2019 Thread Starter
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How do I check for an exhaust leak. If it's bank 1 the leak would have to be between engine and cat right?
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post #4 of 5 (permalink) Old 09-28-2019
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yes the leak would need to be upstream of the O2 sensors, or possibly at the O2 sensor itself . . . . here is the description I found on line that you probably already found too:

the P0420 code stands for “Catalyst System Efficiency Below Threshold (Bank 1).” When you receive a P0420 code it means your catalytic converter is not operating at maximum efficiency. Usually this means your catalytic converter needs to be replaced or there is a problem with your O2 (oxygen) sensors.

I doubt it is dirty MAF sensor, but that is a very easy thing to check -- it is in the intake tube just downstream of the filter, get some MAF cleaner (says on the can), remove the sensor, spray to clean; be careful you don't damage it and install it back in the correct orientation

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post #5 of 5 (permalink) Old 10-03-2019 Thread Starter
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How do I check for an exhaust leak?
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