Would this work to turn off the p0420?

[guybo]

Deleting the primary cat produces a lot of power and deleting the secondary cat produces very little but can cut down on some of the noise of running an open header. Obviously, you need some sort of tuning solution. But of course, deleting the the primary cat throws a p0420 code.

Would this work- deleting the cat in the header and using a Subaru o2 sensor extension harness to move the o2 sensor to a new bung behind the secondary [intact] cat to make the p0420 monitor happy? The existing second o2 bung can be plugged. Would this work to make the power of a catless header but keep the p0420 code from popping up?

[guybo]

This would be for a setup with no ECU reflash so there's no way to turn off the 420 with software alone.

Don't say just get a reflash, this is about doing this some way other than flash or o2 spacer

[IceFyre13th]

Let me think......all this without a tune........OFT tunes for header have the code disabled......naw couldn't work, or will it.....................

[guybo]

Unichip can not turn off codes. I'm thinking out of the box

[Teseo]

Cut a little duct tape and put where on the CEL bright?

[Respect BRZ]

You would have to run both O2 sensors in the correct order via wiring. The code is saying that the cat is or isn't doing its job by comparing readings from the two sensors on either side of a cat. You would need an extention long enough to move the second sensor to behind the 2nd cat.

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[bababooey]

Originally Posted by Teseo

Cut a little duct tape and put where on the CEL bright?

haha, did exactly that cause a.m. wheels with no tpms

[guybo]

I've run with the CEL on with other cars and didn't care, but this car turns off the cruise control when the CEL is on so it has to be off (if I have to manually turn it off occasionally with Torque Pro that's ok but not every day).

I'm thinking of keeping the first o2 sensor in place. I'll plug my wideband a/f gauge into the existing second bung and have a bung welded into place AFTER the secondary cat and plug the second cat into the new bung. The order would be unchanged, just the placement of the second o2 sensor would change.

[mav1178]

Originally Posted by guybo

Would this work- deleting the cat in the header and using a Subaru o2 sensor extension harness to move the o2 sensor to a new bung behind the secondary [intact] cat to make the p0420 monitor happy? The existing second o2 bung can be plugged. Would this work to make the power of a catless header but keep the p0420 code from popping up?

In theory it could work, but you are assuming similar efficiency.

FWIW, the Apex'i setup relocates the secondary O2 sensor behind the cat, and it threw no CEL.



In the front there's a primary O2 sensor bung, as well as one for wideband O2 sensor.

-alex

[guybo]

The efficiency thing is what makes me think this wont work. The second cat just isn't as good at scrubbing the exhaust. The Apexi setup gives me hope it may work.

This is 100% theoretical since doing this would be illegal. Just so everyone knows...

[churchx]

Imho it's just reduced chances to throw CEL just as with "normal" catted aftermarket headers, but no 100% guaranteed CEL elimination.
But i like the idea of adding O2 bung to frontpipe after 2ndary cat to connect sensor with extension cable there. Makes a bit more sense then O2 spacers. As i wanted in future some good catless header + stock catted pipe, considering adding sensor bung to it in similar way.

[Cole]

Or you could just get a proper tune and throw the unichip in the trash, since that's where it belongs.

[Spartarus]

It's a narrow band sensor. The efficiency is not really relevant.

The short answer is yes, relocating the post-catalyst sensor will work.

@Cole, that is sage advice. That unichip does indeed belong in the trash.

What if I told you... Nothing is Illegal...

[ryoma]

it's only illegal if you get caught





(joke btw pls don't flame me)