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P0420 - Cat Converter Efficiency error

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I've gotten the P0420 error a few times intermittently over the last couple of months, the latest being this morning. When I first received the error, I replaced the upper and lower Oxygen Sensors, mainly because I had around 240,000 miles on the car (2004 PT Cruiser) and figured they were due anyway. The car did run better and the error code didn't return for a while.

Now I have over 247,000 miles on the car and it is the original cat converter. I am assuming I am due to replace the converter. The car is running fine. The only thing I noticed was a couple of weeks ago, while driving from Florida to New Jersey and back, is that after stopping to refuel or at a rest stop, the car seemed to not have the acceleration it normally had when merging back onto I-95.

I'll probably be leaning towards changing the converter, but wanted to see if anyone had other thoughts.

Thanks,

Doug
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Discussion Starter · #3 ·
I wouldn't be surprised if your acceleration reduction, assuming it was just temporary, is unrelated to the error codes.
Given that they do seem temporary, I would tend to agree. I am wondering about the possibility the converter is somewhat blocked, and is worse after a short stop.

Thanks for the input.
 

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Discussion Starter · #6 ·
If the P0420 comes back a second time, it is very likely real and time for a cat.
I find 'direct fit' aftermarket converters the best combination of price and fit. 'Universal' cats may be cheaper, but require clamps and pipe cutting/bending and just are just more frustrating to make work right.
Thanks for the input. This is about the fourth time the code has shown up, twice since changing the oxygen sensors. I figured I would use the direct fit cat. Rock Auto has a direct fit from Eastern Catalytic for $196.

Any issues or secrets related to separating the cat from the exhaust pipe?
 
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