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George H.
George H., ASE Certified Technician
Category: Car
Satisfied Customers: 18697
Experience:  ASE Master Tech 15+ yrs, AAS Automotive Technology, Factory trained Asian specialist
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2005 kia rio: engine code..cyl..check engine light..engine light comes

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I have an engine code in my 2005 kia rio 4 cyl that says [ catylist performance below threshold/ bank 1. I replaced upstream 02 sensor but check engine light comes back on with same code.

Hello I will help you with your question,


If you are the original owner you may still be covered under the powertrain warranty for this. You need to replace the catalytic converter as it has failed.


How many miles do you have and are you the original owner?



Customer: replied 7 years ago.
not original owner 98000miles this all started the next day after i sprayed engine off at carwash airflow sensore went bad at same time .I replaced airflow sensore and 02 sensore .airflow code left but not catylist perforemance below threshold/bank1.also replaced sparkplugs egine was missing really bad seems to drie alright now.

If the engine was missing and you have a P0420 code the cat needs replacement as the miss killed it. I'm pretty sure you are out of warranty on this one so you should use an OEM replacement if you want the repair to last. The aftermarket replacements are cheaper for a reason, they only last a few months to a year as they don't have enough rare metals applied to them


Let me know what I can do to help you with this


Thank you



George H. and 2 other Car Specialists are ready to help you
Customer: replied 7 years ago.
is there 2 cats on this car i noticed one on the manifold and one mid way under the car?

There are two cats on your vehicle, the warmup cat in the exhaust manifiol assembly and the main cat under the vehicle.


Which cat is to be replaced depends on which code was retreived fon the computer. Do you know the code?



Customer: replied 7 years ago.

P0420 is the code.

That code is for the cat under the car (Main cat)



Customer: replied 7 years ago.

I would like to thank you for your professionalisam. I could have saved a lot of money if i would have came to you first instead of listening to all the shade tree machanics. If i have any problems with any of my other vehicles i will come to you first.


Glad to help and please let me know if you have further questions


Thanks for using JA!!



Customer: replied 7 years ago.
graphicHi Goerge its me again I was working on my 05 Kia I took cat off and looked inside it seems to be clean i can see threw it good. I went to look inside pipe toward rear 02 sensor leading up to manifold and found this piece of carbon i guess lodged behind rear 02 sensor it also dented rear 02 sensor its about 3" long and 2" round i pryed it out i'm going to see if that was the problem it had to come from manifold cat.

It could be that the manifold cat came apart and damaged the O2 and that is why the code set but it is not likely as the way the code sets is when the front and rear sensors mirror each other in their pattern. If the rear (behind the cat under the car) sensor were dead it would look like normal operation as far as the P0420 code but would set a P0136 code for dead sensor.


Here is what you would expect to see




Your graphic did not come through so if it is a JPG or GIF under 1MB in size please repost using this process. The key is to wait until you see the file appear in the dialog boxes befor pushing the insert button





Customer: replied 7 years ago.

This is what i found and i am hoping it was the problem and that i don't need to replace the cat but i'm not sure what it is and if it would have been blocking things if it would cause the code P0420 to come up?


That is a piece of the ceramic substrate that makes up the active part of the cat.


This is behind the front cat or the rear cat?


Use a flashlight to inspect the inside of the cat and it should be a flat miniture honeycomb that fills the steel casing. If it is melted or broken the cat needs to be replaced



Sorry but it is the only solution.