Catalytic Converter P0420

[JBs02]

Hello,

My CEL went on which I had checked is P0420 code. My car runs perfect, just had the timing belt and fuel filter replaced last month for state inspection.

My question is will it do any damage to the car if I don't fix right away? I won't need an inspection until next April, so I just would like to wait to replace the converter.

2002 S60 Non Turbo, 106K miles

[matthew1]

I've seen this P0420 a few times, I reset it and forgot it. No problems. False positive.

[JBs02]

Thanks for the reply. How do you reset it?

[jpr0204]

Jbs02,

Just becuase you threw a "P0420" code for Cat Efficiency Below Threshold doesn't always mean the converter is bad.

Here is little info that may help:

Converts don't go bad or "die", they are "murdered". Converters are designed to last the life of the vehicle. If one should fail it is becuase something else wrong with the vehicle made it fail.

There are several engine management components that can help lead to converter failure. For example, an upstream oxygen sensor may be giving a poor air/fuel reading to the computer thus the computer may be richening up the fuel mixture and dumping fuel into the engine will will contaminate the converter and make it fail. However, it may not set a check engine light for the O2 sensor becuase it is still getting a reference signal from the PCM and it isn't out of it's "parameter window" far enough to cause the check engine light to come on.

What I would do is if you know how or know someone who does hook a scanner up to the car and look at the "live data" which is real time data this is going on at the exact moment the car is running and look at the different components, like the 02 sensors, if you pull them up and they aren't "switching" or you don't see a waveform pattern and they are "flatlined" they are working poorly and should replaced BEFORE the converter.

Hopefully this gives you a better understanding of the dreaded "P0420" code.

- Joe

[JRL]

Add to the above.
Buy yourself an inexpensive code reader. You can check your own codes and clear this one
I've had this code one of my Volvos for going on three years
Clear it, it comes back. Clear it again and it stays off for 6 months!
Some 99s and 2000s just do this.

(With my car it probably went off at 48K miles because the PO had a new converter and both O2 sensors replaced a bit before we bought it
I can't believe anything is wrong with the R but after 45K miles since the new converter was installed it started doing this again.
Now almost 15,000 miles later, it still goes off every 6 months or so but will clear and stay cleared