OEM Catalytic Converter vs. aftermarket?

Question

I replaced the CC on my 2001 Grand Prix about one year ago. I now have a 0420 code once again. I have been assured that this code only relates to the CC & that a faulty O2 sensor would not send this code. Flow was mentioned though. That the flow through an aftermarket converter may give the O2 sensor the bad reading, or the converter could actually be bad again. I don't want to go to the dealer so how do I find what exact CC was OE to my vehicle? Or any other thoughts besides the OE Converter are appreciated...

Answer 1

I could very possibly be a collapsed muffler, especially on a GM. This would cause too much back-pressure and heat, and bad readings.Stand behind it and feel the exhaust. Or the top speed would be affected.

Answer 2

you have a o2 sensor before and after the CC. If the computer thinks the o2 sensors are operating correctly then it says the CC must be to blame. But that does not mean the o2 sensors are really operating correctly.

The manufacturers suggest you change o2 sensors every so many miles--i guess theres a reason for that.

I dont have all the answers, but thats how i see it.

Answer 3

the cat.is essentially an oxygen generator.once it is depleted of oxygen generation ability it may post a P0420 code.This does not mean that the cat. is bad!.Anything that can cause a rich running condition IE worn spark plugs and wires are a major cause,because weak spark will not burn all yhe fuel supplied.Vacuume leaks or lazy upstream 02 sensors can also cause problems.                                                                                              The cat can only generate so much oxygen to oxidize un-burned fuel and once you surpass the capacity the computer "assumes" the cat.is "worn out or bad" if all the basics are good,IE complete tune up,no vacuume leaks 02s check good then maybe you can condemn the cat.You may need to have a professional diagnose the causeto be sure.Besides most aftermarket cats.carry a 50,000 mile replacement warranty.

Answer 4

Aftermarket converters contain a lower percentage of the precious metals needed for a cat conv. to function properly. As an example take an original equiptment converter to a recycle (scrap) yard and see how much more it is worth versus an aftermarket conv.

There are things that could have caused this conv. to fail prematurely also, such as a cylinder misfire  ..etc.

  Cat converters carry a warranty by law in the US, take it back to where you purchased it.

Answer 5

look on ebay for an oe CC but if the CC is bad it will make a wired Sound

Answer 6

That code means the O2 sensor is reading too much oxygen coming out of the back of the cat. It could be a bad cat or a bad sensor. It's a lot easier and cheaper replacing the sensor first