P0420 code “Catalyst System Efficiency Below Threshold (Bank 1).
Changed 02 upstream sensor
Reset code by disconnecting battery 1 hr
Check engine light has been going on and off since not blinking. But in for ahile then off. Usually comes on while driving then off next time I start it then back on as driving.
You probably need a new catalytic converter, but a shop can determine for sure. Not super expensive unless you live in California and have to buy a OEM spec part.
Does this vehicle have ANY exhaust leaks? You cannot have any leaks in the system.
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None that. I have noticed, I will definitely have to check thoroughly
The same code came up on my old 02 Camry. I replaced both o2 sensors and never had another problem. Gave the car away 75k miles later still no code.
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Replacing one of the two O2 sensors isn’t the way to go… the two sensors basically compare notes, so one can throw off the other.
I’d try what @PvtPublic did and see whatchagets