P0420

My 2005 Buick Century with 353k miles gets a recurring P0420 code, catalytic converter operating below efficiency level. Twice this year, I tried using Cataclean, but with no success. I noticed a small hole in my muffler at the seam. Could a lack of exhaust back pressure cause the CC to operate inefficiently or improperly? Can anyone recommend a catalytic converter cleaner? Or, is it all snake oil?

No, lack of backpressure has nothing to do with your issue. You need a new catalytic convertor most likely

I am trying to troubleshoot a 4runner with 135k miles, auto, 3.4 V6 California emissions. This is the freeze data: PID Description Value Units 0x02 Freeze frame DTC P0420 - 0x03 Fuel system status Closed-loop, using oxygen sensor feedback to determine fuel mix - 0x04 Calculated load value 34.12 % 0x05 Engine coolant temperature 197.6 F 0x06 Short term fuel % trim - Bank 1 0.78 % 0x07 Long term fuel % trim - Bank 1 3.91 % 0x0C Engine RPM 2287 RPM 0x0D Vehicle speed 68.97 MPH 0x0F Intake air temperature 95 F So far the front and back Ox sensor was replaced and the MAF cleaned to clear a P0171 co

Has DTC P0171 stayed clear after a 2 trip minimum? Did DTC P0420 come back after it had been erased? The freeze frame short and long term fuel trim is way out of wack. The PCM is trying its best to lean out the mixture but is close to its limit. You will have to find out where the extra fuel is getting into the engine – think leaking fuel pressure regulator, stuck fuel injector, leaking fuel injector, MAF out of calibration, etc. I would be striving to get the long term fuel trim close to 50% before I would condemn the catalytic converter. Can your scanner read the activity of the A/F and o2 sensors? If you have the equipment, use an dual trace oscilliscope to monitor the A/F and o2 voltage wave forms and see if they are similar in rich-lean-rich crossings. My research has led me to unders

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