UEL Catless header + oft ST2 fail smog
 

Im failing smog with this tune is what I am being told, I did 3 drive cycles fully, hoping to pass emissions. I'm wondering if I flash back to stage 1 and do a drive cycle with the uel catless header still on my car, is that possible? I don't want to damage my car. Or do I have to take the the header off and put my stock back in?? which I really dont want to do...
sorry i am very new to this, any help is appreciated, thank you

If they are looking for readyness checks to show pass you willlikely never get all readyness checks to pass with any tune that disables the P0420 cel code. And with a catless header fitted.

I believe disavling ghe P0420 cat efficiency code will cause some readness never to pass, also readyness actually analysises the signals from front and rear 02 sensors amd want to see certian patterns.

You might be avle to fool system by flashing a tune without P0420 disavled, but you might need to install an 02 spacer in rear 02 sensor to fool the checks as well

In the end you may need to install stock header and tune to pass

So is this an issue a lot of people deal with? I’m pretty sure in the county I live in they don’t even plug into the obd2 port. There are no emissions checks in the county I live in.

Mostly a California thing. In fact from what I understand he is illegal with just the header installed, even if it had a cat in it.

Yup. No ARB EO, not legal in CA. Highly doubt even when aftermarket companies make catted headers that do pass, that they would bother to pay for the testing to get it stamped. Filling for an EO is free otherwise.

I can pass the visual inspections, its just that im having the oxygen sensor code with another error. Is it safe to go back to Stock tune or should I go to stage 1 tune with my catless uel header? I might try that to see if i can pass. but i dont want to tune my car if its going to hurt it, please let me know, thank you

No you are gettin lucky you pass with a visual! Sounds like it is just a matter of time before someone knows what a stock header looks like.

so i cant change my tune to stage 1 or oem tune with my catless headers?

to answer your question from what i have read, it seems others have not been hesitant to have aftermarket headers & ran either a stock tune or stage 1 tune. some even claiming they didnt get cel, but those reports were the minority and depended on what brand was used. i'd suspect it would not grenade your engine running it short term, just dont get crazy on the rpms/ load.

You can. What everyone is saying is you likely still won't pass. If you have your stock header why even mess around, just swap it out for your smog test. The stock tune with still throw the CEL for the O2 anyway.

Until you disable the CEL for the O2 sensor you will never pass.

i live in vegas so they dont really care for visual testing, im wondering if i can still pass the codes if i retune it back,

If you are getting the CEL on your tune now, you will still likely get it with your stock tune unless you disable it, or put the stock header on.

I'm confused. OP says he's in OFT Stage 2 tune which disables the CEL. He does not have a CEL. The problem is that despite this, the OBD shows a readiness fault.

So the only way to pass is to put on a stock header and flash back to a stock tune/tune that does mot disable the CEL.

Right?

yea i have the stage 2 tune with tomei uels catless, no cel, everythings fine, but the smog says other wise. i dont have my stock header anymore, so last thing i want to do is find one to switch it out, trying to avoid that. visual testing is fine i passed, but the smog doesnt pass me for readiness. i have 2 errors