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P0420 - 2002 Toyota Camry

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.

1 Like

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