My check engine light came on so I took it over to auto zone they told me the o2 sensor downstream was bad so I replaced it check engine light went out for a day came back on im lost...
Well what is the new code. If it is the same one then you will have to have the vehicle "live data" scanned, that way you will know if it is the new sensor or the catalyst going bad. If it is a new code then you will have to diagnosis that one and proceed from there.
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