P0420 code after installing header on my kia

[vg_Ace]

So I am not finding any answers on my kia forums so I thought I would ask you guys. Besides owning a 91 crx HF I also own a 2005 Kia spectra 5. I recently bought a header and midpipe for the car. After waiting 5 months I finally get it. The stock setup was as follows:

Exhaust manifold with 1st 02 sensor, catalytic converter, downpipe, midpipe with Flex part and after that 2nd 02 sensor, cat, resonator, more pipe and muffler.

The header and midpipe eliminated both of the cats. Not only was this freakishly loud, but it is also now throwing a P0420 code. I was advised to buy an 02 extender off of ebay. It costs $9 and $4 to ship. Needless to say it is crap and does not do anything. It may work for your car but it did not work for mine. I already had my stock cat welded back onto a section of the midpipe closer than it was during stock configuration but it is still behind the 2nd 02. What I am going to do now is go to the same exhaust shop and have them drill a 02 bung behind the cat. Then I will ahve to cut and splice in more wire to physically extend the 2nd 02 sensor BEHIND the cat. I was told that the distance matters by some and that it doesn't matter if it is right behind by others. Anyways I will see what the shop says.

My question is this: what care should I take when extending the wires? I already have the correct gauge wire, and I am going to solder and heat shrink the wires to give a good connection, but is there anything else I should worry about? I mean has anybody that owns a Honda ever had a P0420 code thrown for something like this? What did you do? Thank you all for reading.

 

[AHHVTEC]

i have no clue what that code is but i bet its just saying hey wheres the cat at, so its no big deal, the 1st o2 sendor needs to go before the cat the 2nd on needs to go after, then the light should go away after you reset the ecu, those o2 sensor de fouler sometimes they work sometimes they dont..

 

[vg_Ace]

I have been doing some research and there are multiple ways to solve this problem. I already bought a 02 extender which didn't work. It keeps throwing codes. The ebay seller told me to buy another extender at an autoparts store and that will move the 02 sensor further away from the pipe. This will cost me about 5 bucks max. Or I could go and get a 02 bung drilled and just extend the wires and move the sensor behind the cat and let the sensor do what its supposed to do.

 

[AHHVTEC]

well if you have a cat on your car then i would just let the sensor do whats it needs to

 

[LS_VTEC]

Some aftermarket headers will only have one bung for an o2 sensor. Depending on whether your car has two o2 sensors is the question. The first o2 sensor (near the manifold), is bank1 sensor 1. Usually a heated oxygen sensor at that. That is what sends signals to the ecu/pcm and lets it know if it is running rich/stoich/lean. The second o2, which is bank1 sensor 2, is just to send a signal to the ecu/pcm and let it know that the cat is functioning properly. Has to do with NOX and emissions. Just make sure it has both o2 sensors in, and in tight.

 

[vg_Ace]

ok another update. I have solved the p0420 code. If you buy a 02 extender like I said off of ebay it will not work. It wil still throw the code. This is because it is still getting enough exhaust to read that there is no catalytic converter. BUT if you buy a small spark plug nonfouler and extend it even FURTHER out it will stop the P0420 code. In fact it works so well that it will throw a P0140 code. This means that there is simply not enough flow of exhaust for the 2nd 02 sensor to read anything. Here is what i am going to do then. I am going to drill out the spark plug nonfoulers in hopes that the 02 sensor will still read exhaust, but that it will different enough from the first 02 sensor so that it won't throw a P0420 code.

Heres a pic of the non-fouler