Cobb Downpipe Code P0421

[AhSaol]

Hi there, after installing the COBB Downpipe I get this P0421 Code sometimes. How can I get rid of it? I have no AccessPort. Would a defouler help on the second o2 sensor?
I searched a lot for an answer butr couldn't find anything really helpfully.
Regards

[RACER_X]

Um get an AP

[AhSaol]

I'm just wondering because the UR Downpipe did not throw a CEL

[MazdaBoy2.3]

Is it catted?

[AhSaol]

Yes, it's catted

[MOCO MS3]

Check the Downstream O2 Sensor.

[littleloogy]

Install a bung at the second o2 sensor.

Sent From a Galaxy, Far Far Away...

[Reggaeboy143]

Originally Posted by AhSaol I'm just wondering because the UR Downpipe did not throw a CEL

yeah my UR did it like two nights ago.

Originally Posted by littleloogy Install a bung at the second o2 sensor. Sent From a Galaxy, Far Far Away...

what kind of bung?

[g00s3y]

Just get an AP, if you already have internals and a DP, there is no reason not to tune...

[littleloogy]

Originally Posted by Reggaeboy143 what kind of bung?

A bung-hole. The Official Downpipe/Test Pipe/Race Pipe Thread

Sent From a Galaxy, Far Far Away...

[GregScuba]

@AhSaol; any word on how the bung extender worked? I also Installed a brand new catted DP from COBB recently, running stage 2 OTS map on the AP (see sig for other mods) , and am getting a p0241 code as well (catalyst warm up efficiency below threshold). It seems to pop up once or twice every few days. . I checked all of the connections and bungs for signs of leakage (carbon), nothing that I could see. Tried reseting the ECU, to no avail. I called and spoke with Adam at @Cobb;. He said it could be a bad cat, but highly unlikely given it being brand new. He said it could also be bad spark plugs or improper gap, and instructed me to check the plugs (brand new NGK Iridium 1 step colder, gapped to .026), and then if that doesn't work, to try replacing the secondary 02 sensor.

I'll check the plugs and report back. Might be a good time to check compression as well (95,xxx miles on the clock). Best price on the secondary 02 sensor seems to be at Rock Auto for around $70 for OEM NGK unit. The other alternative would be to just ignore it as a fluke if everything else checks out okay and untick the code in the AP. Thoughts?

[AhSaol]

It did not happen again to me, but it's warmer outside now. Maybe it will return in winter I don't know, I did not use the extender.

[mituc]

I went through the same issue and there's no clean way around it unless you simply deactivate that error from the Cobb AP or versatuner.
This spring I replaced the 400cel ceramic cat with a 200cel metallic cat with 60g load that are usually used around here for Porsche 991/996 sport exhaust systems and now I pass emissions and also reactivated that catalyst efficiency error checking when flashing the tune. All is great, emissions control system works like the factory.

[GregScuba]

Check the plugs, perfect gap and appearance, did a compression test, all cylinders between 195 and 200psi. Went ahead and unticked the code in Accesstuner. Something interesting I noticed, was that p0241 is already unticked in all the OTS maps for 91 octane fuel from Cobb. This leads me to wonder if maybe fuel quality may be a factor.

[mituc]

It's not the fuel, it's not the plugs, it's not the compression. It's the cat.
You can use a bung for the secondary O2 sensor and make the error appear a lot less often or not at all, you can suppress that error code in the tune or you can replace the cat with a proper one.

[GregScuba]

Yeah, that's kinda what I figured ultimately. Just doing as Cobb instructed, that way if any major issues come up, I've covered myself and followed through properly.

The whole thing just kinda took me by surprise, given the otherwise outstanding build quality and reputation of this DP. I'm pretty much over it though, and am content to just untick the code in AP and not look back or worry about it ever again... unless, of course, I move to a state with strict emissions testing in the future, then I'll look into a bung extender or changing out the cat at that time.

Thank you for your insight. It's very much appreciated.

[GregScuba]

Just a quick update... Since finishing up tuning with Stratified Automotive Controls last month, the problem no longer occurs at all, no codes, and no pending codes either (as one would see if it were unticked in the programming). All emissions systems pass my scan tool's testing. To those our there with a Cobb OTS map, please, do yourself a favor and get it properly tuned. It will run so much better, and will be far safer in the long run. The tune is well worth it, and a sound investment in your car's longevity.

[mituc]

Once you get a code you get a code, it's crystal clear, there's no way of tuning around it unless you disable the code from the ATR/Versatuner.

[allservice]

@mituc; , what exact part is that catalytic converted for Porsche you mentioned?

[MSMS3]

Originally Posted by allservice @mituc; , what exact part is that catalytic converted for Porsche you mentioned?

You do realize you are responding to a four year old post expecting a reply?

You might try PM’img him. I think he is still around.

[mituc]

Originally Posted by allservice @mituc; , what exact part is that catalytic converted for Porsche you mentioned?

That's ok, I'm still around.

So They didn't actually get a Porsche OEM, but something they replace the OEMs with. In the meanwhile I shattered that one, it was pretty weak. The high frlow cats the guys from Ultimate Racing are using in their DPs and TPs work fine for me. They are magnaflow 59959. However I noticed that the exhaust smell becomes more and more noticeable with time with these cats, so now I'm going to buy an EURO6 cat which will cost me about $900. From my knowledge I still have the record for the most powerful and quickest 2.3DISI-T powered car fully emissions compliant and I intend to keep it, so for me it worth the money. Otherwise the Magnaflows will be just fine.