**CEL after catless downpipe install, HELP ME**

if the car was excessively rich or lean you would get a fault that specifically says so if it has to adjust the fuel trims to far from the normal operating range.

Stage 2 is optimized for having a higher flowing downpipe. Stage 2 does not get rid of the cat faults, a test pipe file does. You can get the stage 2 test pipe file and you will not get faults for the cat, but it's a federal crime to remove a cat from a car and the readiness monitors will never set which in means in most states you'll fail emissions. Or you can get a stage 2 non test pipe file and try different spacer setups until it stops throwing faults for the cat.

I would do spacers till you get the cat to pass to the test and not throw faults, then you can get an APR flash that will have a test pipe file for stage 2 but when you put it in stock mode it will look for the cat.

yeah, no inspection here tho so i should be ok. i may pick up a cat to swap in just whenever i want. i just ordered the die i need to make the M18 thread for the spacer. so i'll probably try makin it in the next couple days. but thanks for the reply, ur d best haha

DBESTGTI said:

if the car was excessively rich or lean you would get a fault that specifically says so if it has to adjust the fuel trims to far from the normal operating range.

Stage 2 is optimized for having a higher flowing downpipe. Stage 2 does not get rid of the cat faults, a test pipe file does. You can get the stage 2 test pipe file and you will not get faults for the cat, but it's a federal crime to remove a cat from a car and the readiness monitors will never set which in means in most states you'll fail emissions. Or you can get a stage 2 non test pipe file and try different spacer setups until it stops throwing faults for the cat.

I would do spacers till you get the cat to pass to the test and not throw faults, then you can get an APR flash that will have a test pipe file for stage 2 but when you put it in stock mode it will look for the cat.

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Good advice for anyone w/ emissions testing in their state. Unfortunately, playing w/ spacer setups is NOT fun.

DBESTGTI said:

The reson for the CEL is not because the exhaust moves to fast to read, that's completely false. The front 02 reads the air fuel ratio and relays it back to the engine constantly so it can adjust the fueling constantly. The rear 02 checks the exhaust again to make sure the catalytic converter burned up what the engine didn't. It monitors tha cat effeciency. You get a check engine light because you removed/downgraded the cat from OEM and its boy as clean and efficient anymore. The point of the spacer is so only a small bit of the exhaust makes it to the rear sensor so it's tricked it into thinking a small sample is clean exhaust.

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But now tell me is it better to get that spacer to trick the 2nd 02 sensor to get rid of the dash light or would it be better to just go stage 2 and leave the 2nd 02 sensor tucked away?

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sogeo09 said:

But now tell me is it better to get that spacer to trick the 2nd 02 sensor to get rid of the dash light or would it be better to just go stage 2 and leave the 2nd 02 sensor tucked away?

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Best bet would be to go stage 2 with the file that disables the sensor all together. However if you cant afford to go stage 2 or what have you you can try your luck with a spacer and see if it hold your CEL at bay for awhile. Or just live with the CEL.

sogeo09 said:

But now tell me is it better to get that spacer to trick the 2nd 02 sensor to get rid of the dash light or would it be better to just go stage 2 and leave the 2nd 02 sensor tucked away?

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If you need to pass inspection, you'll want to beat the code not skip it. Otherwise you'll need to go stock downpipe before you get inspected (if emissions is tested).

So I'm APR stage 2 but still get this code. Any help? Also BB catless exhaust, calling out bank 1 too rich

Flipper said:

So I'm APR stage 2 but still get this code. Any help? Also BB catless exhaust, calling out bank 1 too rich

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i think APR has 2 files one as a test pipe (disables the CEL from the cat) and one with readiness enabled used with a catted downpipe where the code can come up.

You can take it back to your APR dealer and have them re-flash it if thats the issue or they can better diagnose if something else is wrong.

For me, I finally found what works for my CBFA MKVI GTI with catless turbo back exhaust. The exhaust is from Baluga Racing and I had to modify it slightly to fit the CBFA engine. I have a straight spacer on senosr 2 like this Doorman.

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/161119594890

On sensor 3, I have the 90° spacer from ecs (style) like this one with the smallest inlet on it

https://www.ecstuning.com/b-vibrant-performance-parts/j-style-oxygen-sensor-bung-spacer/11619~vbp/

Now this setup threw a cell initially for cat inefficiency so I added a straight spacer to the 90°. It's been several thousand miles and I have not seen the light since. Everything shows ready and no light. Also my tune does not have the cel delete as it is useless to me in NY.

I actually made an account here just so I could post this because I know how frustrating it can be. Hope it helps someone.

I put a cheap $14 ebay unit on my 2nd, post-cat position, O2 when I went catless...it worked. Aimed it forward and up a bit. I do not think just a stage 2 tune will eliminate the code, but didn't read every post to see if this was eventually done and if it did work.

I did that in an Audi A4 that I owned previously and it worked great for years without a single CEL. The problem that I was having with my '13 GTI (as well as many other owners) is that I was "blessed" with the CBFA setup. This model was produced (I don't know how many years) with either CBFA or CCTA. I don't pretend to know all of the differences but the major one that pertains to a TBE is that there are 3 O2 senors on the CBFA as opposed to only two O2 sensors on the CCTA. On the CCTA you have one O2 sensor pre-cat and one O2 sensor post-cat (same on my old A4). You fool the post-cat O2 sensor by removing it from the stream with a spacer and all is good. on the CBFA you have one O2 sensor in the turbo housing, a second O2 sensor after the turbo muffler (looks like a small cat on the inside) this is also pre-cat, and a third O2 sensor post-cat. I assume ( I am by no means a pro so someone please feel free to correct me) the the first O2 sensor is sampling the raw exhaust. The second O2 sensor is making sure the turbo muffler is cleaning the gasses a little, and the third O2 sensor is making sure the cat is sufficiently cleaning the exhaust the rest of the way. I just figured that I would mimic that with spacers. So far the only thing that has worked and kept the cel off for me is the straight spacer on O2 sensor number 2 and the J spacer with smallest hole PLUS a straight spacer on O2 sensor 3. Hope this all makes sense.