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Stage 2, downpipes, and NYS Inspection explained.

Posted on June 02 2020

Getting right down to brass tacks here about how all of this works - but first:

Disclaimer: The following information is presented in order to dispel myths and provide clear, factual information. We are not going to address any of the legality, as your application may vary. Titan Motorworks reminds you to follow all applicable state and federal motor vehicle codes/laws. What you do with this information is on you.

Glossary of terms:
NYSI: New York State Inspection
APR: Software tuning company
CEL: Check Engine Light
Readiness: a pass/fail state of your vehicle emissions self-test system.
Cat (catalyst): Emissions component that scrubs your exhaust gasses.
O2 sensor: Sensor that registers emissions information.
Downpipe: usually the exhaust section containing the catalyst and O2 sensor.
Catback: The second half of your exhaust; not emissions related

This is a book, here's the short answer: You CANNOT pass a *standard* NYSI on a Stage 2 testpipe file. Doesn't matter if you know someone. Below, you'll find every variable and explanation.

Stock Software/Stage 1 + Stock downpipe = Pass
Stock Software/Stage 1 + aftermarket downpipe = Fail
Stock Software/Stage 1 + aftermarket downpipe + spacer = Pass
Stage 2 + anything = Fail

For those of you learning, stage 1 software requires no hardware changes to your vehicle. It is the most popular software option we see. Stage 1 alone will not impact your ability to pass a NYSI, at all.

Stage 2, for *most* vehicles, implies upgrading the main exhaust component controlling flow - the catalyst section. This may be a singular compact unit (many 2.0T longitudinal), or a larger unit (most transverse 2.0T). In several cases, a manufacturer may include more than that -  APR's downpipe for the longitudinal 2.0T vehicles goes from the turbo all the way down below the car, to the OEM clamp at the catback. Meanwhile, EuroCode replaces just the upper catalyst section alone. This is frequently why we see such price discrepancy. Then, on other platforms like the B8 3.0T, the 'downpipes' are totally unrelated to the catalyst section, and really should be called link pipes. Anyway- be ready to ask the question of WHAT you're actually replacing.

Aftermarket downpipes may contain a catalyst, or may not. For the sake of the conversation, MOST aftermarket downpipes that DO have a catalyst... will still throw a check engine light. AWE, Milltek, and HJS are on a short list of brands that offer -specific- product that will NOT throw a CEL. So, for the real-world simplification, let us assume that all aftermarket downpipes will cause a CEL, ok?

If your car was stock, and you had no CEL on, you could get an inspection any day and pass with flying colors. Now, if you go Stage 1, you're still in that boat. Go get an inspection any time. If at this point, you add a downpipe, the car will soon thereafter, throw a CEL. That code is almost always a P0420, indicating "catalyst below efficiency threshold". This means your rear O2 sensor knows that factory cat isn't there any more. Now, you can't pass NYSI because your check engine light is on. Remember, NYS is a one-fault, no CEL state. You can have a single fault code as long as the CEL isn't on.

So here you are, with your new downpipe, and a check engine light. Sucks. What do you do? 

Well, a lot of people will say go Stage 2. They're sort of right. Stage 2 'testpipe' files from APR will disable the rear O2 sensor from reporting the code; yes. This will turn off the CEL for the P0420 code. For the record, if you get any other codes - lean, rich, stuck, etc... you've got a different problem. Cheap downpipes tend to leak, which means they either suck in extra air or leak it out. Same with bad gaskets or reusing the stock gasket during install. Anyway, different issue. Back on track: Going 'Stage 2 Testpipe' will turn off the CEL for the rear O2 sensor, and let you get back to seeing it come on for OTHER scenarios. So yes, this is why it's a good idea - so if a different issue were to occur, you wouldn't potentially ignore it, thinking it's just for the downpipe.

Downside- Stage 2 testpipe files will, by default, prevent you from passing NYSI. This is a computer issue, not an "I've got a buddy...." sort of scenario. The software will disable the readiness monitor system, which means at no point ever, is your car in the 'Ready' state it needs to be in for it to pass inspection. When you go somewhere for an inspection, they plug into the car for that test. A tech can't interfere with that. No amount of driving or code clearing will change it. You'll need to switch the software. We offer to flash a car back to stock at no charge for this sort of scenario, and yes, you can get your tune popped right back in at no charge afterwards. 
**The only exception to this is when a brand-new vehicle gets its first two inspections. In NYS, the first two are just 'safety' checks, which means as long as the CEL is visually off, they pass the car. This is frequently where people start to debate, saying that so-and-so passed while stage 2. This law came into effect in late 2014, so prior stories don't count either.**

Ok, so now you're sitting here, with your CEL-throwing downpipe and an expired inspection. Not great. But that's ok! Sure, you could remove the downpipe and go back to stock, drive a few days, set readiness, and pass inspection. Ehh, that's work. You can also find an O2 sensor spacer (we recommend a specific one I can't advertise here), which will convince the sensor to turn the CEL off. It is -real- important to recognize that MOST of the sensor spacers on the market do NOT work well. That's why we have a specific recommendation.

So, you install your O2 sensor spacer on the DOWNSTREAM sensor, which is the one farthest away from the engine. Now you need to set readiness. If you're trying to do this as fast as possible, clearing the code is the first step. Some vehicles have different criteria to hit in order to set all the monitors. It's just JUST driving around. Typically you need your fuel level to be between 1/4 and 3/4 a tank, so not on fumes or recently filled. You'll need to log about 15 minutes of steady cruising at or above 50mph, withOUT using the cruise control. It will help to have the AC turned on (in the winter, just run the defroster, as that uses the AC to dry the air- which is also why you see the AC light on mid-winter). The vehicle will also need a cold-start, which means your coolant temp basically needs to be the same temp as the outside air. Park your car overnight and when you start it in the morning, you'll start that test automatically. Drive the car a mile or two now, and in MOST cases, you'll be ready to rock. Typically these same tests will not run below a certain temperature, so if its a frigid day in January in Rochester, you might be SOL. There can also be other underlying issues, or conditions not met. Like when you ignored me above, and got a crappy spacer, and it didn't work, and now you're late to work because you got stopped for an expired inspection. Told ya.

So now you've got no CEL, and you're looking good. Keep in mind that if you do not have a -visible- catalyst, you won't pass the -visual- inspection. If you're knowledgeable, this may not be an issue. Go get inspected. Got your sticker? Great, get reflashed back to stage 2. You can leave the spacer on, but they don't last very long. If you opt to leave it on, you can often add in APR's 'Switchable Program Feature' for an additional $149. This unfortunately is not available for all cars at the moment, but the range is expanding. Anywho, if it is, it will allow you to load up to 4 files on your car -- including the option for a Stock-Non-Test-Pipe file... which means you yourself can switch between the sensor-enabling-inspection-passing software, and the other stage 2 file, whenever you want. You'll still need to play by the above rules, but it saves you the multiple trips to us. Not that we don't like seeing you or anything. You know. 

Still have questions? Scroll back up - use the simple chart. Then call or email us and we'll confirm for you!



  • KDH: October 03, 2021

    Am I really stuck at APR stage 1 in my S8 D4? All information I have received is that I can’t get anything else from APR to update my tune unless I go DS1 or another software.

  • John Frame: December 10, 2020

    AJ, you are correct that Stage 2 “Non-Testpipe Files” will allow monitors to set, yes. However, not every vehicle has the option for non-testpipe files.. this is the safer explanatory answer. Beyond that, popular usage of the term ‘Stage 2’ would imply running a downpipe that would not naturally pass inspection, and thus running a file that disabled the readiness monitor. For the sake of clarity to the masses, it’s written the right way.

    Once you get down into the technical, and check availability, yes, the limited number of stage 2 non-testpipe files are great for exacting scenarios. We’re actually responsible for a mass of those non-testpipe files, as we started dealing with the 1-fault NYSI in 2014.

    Furthermore, as APR has discontinued all issuance of stage 2 files, this is only relevant now for existing, grandfathered-in users, who are certainly familiar with the hassle now.

  • AJ: September 28, 2020

    This is incorrect: “Stage 2 + anything = FAIL”

    With an APR downpipe, the APR stage 2 (non test pipe file) tune and an O2 spacer (that does what you need it to do), you will pass NY State emissions. The APR stage 2 non test pipe file enables the sensor/monitor – this is why without a spacer, you will get a CEL/code on this version of their tune.

    Two years ago I reflashed my APR stage 2 test pipe file tune to a non test pipe file tune and a CEL appeared. I proceeded to install an O2 spacer, reset the codes and drive 100~ miles in an attempt to pass emissions. No CEL after 100~ miles/no code, so I went to get emissions checked. Not only did I end up passing NY state emissions that year but a year later (this year) I passed again. I did not modify anything since the first time I passed. My car still has an APR downpipe, the APR stage 2 non test pipe file (confirmed by APR, provided them with the last six of my VIN over the phone) and an O2 spacer. I do not have a CEL/my car has never thrown a code since installing the O2 spacer after the reflash.

    Using VAGCOM I can see all monitors are in a READY state. So…

    APR stage 2 (NON TEST PIPE FILE) + APR downpipe + O2 spacer = PASS

    You should do a bit more research it seems :)

    2018 Volkswagen GTI DSG S

  • Franchesca Petersen: August 27, 2020

    Is there anyway you can divulge this sensor info. I’m in the situation as described but I didn’t do it to my car the previous owner did, so I’m trying to just make do with what’s been installed

  • Kelly : July 10, 2020

    When y’all come out with apparel please let me know!!!!!!

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