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.
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.
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