Catalytic Converter and O2 Sensors p0420, 1166, 1167

[ace of spades]

a new secondary will still be cheaper than a cat so maybe I'll try that.

I'm at 94k now, so that's out.

[talonXracer]

LOL, it probably started going bad at 80,001 miles


BUT, what you can do, is get one of those secondary extensions and just fake the ECU/OBDII system into thinking the cat is good, the same as if you were to remove the cat and installed a race header without a cat.

[ace of spades]

LOL, it probably started going bad at 80,001 miles


BUT, what you can do, is get one of those secondary extensions and just fake the ECU/OBDII system into thinking the cat is good, the same as if you were to remove the cat and installed a race header without a cat.

also a good idea

[Tasteful]

Where could i get such an extension? I've heard mixed things about them, people saying they "dont do the trick". What are the odds it would get rid of my p0420 and 1166/67?

Thank you for all the explanations. i've learned alot in this thread so far!

[talonXracer]

The extensions do work, just not in all cases with every type of extension, the ones with a 90 degree offset seems to work fine, the DIY version made with defoulers can have questionable success.

[ep3jd]

My dad gave me one that's just a straight like 2"extension, didn't work.

[talonXracer]

If the bottom hole on the extension is too large then it doesnt isolate the secondary sensor. The entire purpose of the extension is to move the sensor far enough out of the direct exhaust gas flow that it THINKS the cat is operating normally. And seeing that every sensor reads slightly different, what works with one sensor MAY not work with another sensor due to that variance.

[Tasteful]

What would you recommend I do? Is there a specific one you'd recommend? with codes for o2 sensors following my code p0420, efficiency below threshold, should i get a secondary/post-cat sensor or just a simulator?

[Rasy]

I initially had a p1167 for the pre-cat A/F sensor, then it changed to an on/off p0420 for the cat.

Tried a secondary, post-cat sensor, disconnected and reconnect the battery to reset the ECU and clear the code, and my cel (p0420) went away for good since.

[SkareKrow]

swapping out the primary would do absolutely nothing for your issue other than to lighten your wallet.

Any CEL that is cat related is either the cat or the secondary sensor if there is no error codes for the primary at the same time.

These CEL's are generated when the temp of the exhaust gases are not lower at the secondary location when the ECU compares the temp between the primary and secondary sensors.


Your cat is covered by a 8 year 80K mile warranty, if you are below those points you can get a new one for free.

Is there a way to by pass the CEL from turning on? In other words if you have a "test pipe" What to do? just curious. :) Thanks Talon!

[ImportCustomx]

moved to the correct spot

[StockTexasEP3]

I have a test pipe and am throwing a few of these codes myself. I have a DIY defouler on the second sensor. Any ideas? Maybe a bad sensor?