# Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has this DTC and wich DP/Cat



## 20V1.8Tnut (Dec 31, 2000)

I need some statistic on 16804 DTC here. Also, please post how you solved this issue or if you think there are some solutions for this DTC. Please post if you have an aftermarket DP/Cat combo and never had this DTC stating for how long you have you combo.


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## [email protected] (Jun 5, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

I know this isn't a choice, but I used the ATP 3" DP/Cat for 20,000+ miles in my AWD engine and never threw that code.


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## 20V1.8Tnut (Dec 31, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

bump


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## evilpat (Feb 26, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

My car threw that code just last night and I have a stock exhaust. Is it intermittent or does it come back as soon as you clear it?


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## 20V1.8Tnut (Dec 31, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (evilpat)*

It is never comes back immediately after you clear it, but will come back after ECU will detect this DTC a few times.


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## evilpat (Feb 26, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

So the CEL is intermittent but the DTC is pretty much always there? Have you tried putting the stock DP/cat back on? If it doesn't throw any codes then most likely it is a faulty cat IMO. Then you can just give them a call about it. http://****************.com/smile/emthup.gif


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## dbrowne1 (Oct 31, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (evilpat)*

My FM started doing this a few months ago after 8-9 months of no problems. I'm also getting an upstream O2 sensor code. CEL is intermittent, codes are there a day or two after clearing. No exhaust leaks (I checked carefully).
Think my O2 may be dying. MAF is cleaned regularly.


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## Audi tech (Jan 7, 2003)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (dbrowne1)*

Cat efficencly below threshold is usually an exhaust leak by the post O2 sensor, and it's usually at the clamp that connects the down pipe to the rest of the exhaust. If there is even a small leak, then under deacceleration there is a pressure gradient that is created. And, then the air outside is then "sucked" back in to the exhaust system for a split second.


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## LA Wolfsburg (May 8, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (Audi tech)*

GHL DP no CEL


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## Cypher2k (Nov 23, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (Audi tech)*

Mine is cause by cruising below 2500 rpm for too long with a 3" HF cat.


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## 9VW23yrs (Jun 22, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (Audi tech)*

Could this leak kill the catalyst or 02 sensor in the long term? 
quote:[HR][/HR]Cat efficencly below threshold is usually an exhaust leak by the post O2 sensor, and it's usually at the clamp that connects the down pipe to the rest of the exhaust. If there is even a small leak, then under deacceleration there is a pressure gradient that is created. And, then the air outside is then "sucked" back in to the exhaust system for a split second. [HR][/HR]​


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## Audi tech (Jan 7, 2003)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (9VW23yrs)*

In theory, it could destroy that cat over time. With the rapid heat and cool shocks that could happen, the substrate in the cat could deteriorate and break up. I've never seen it happen, becuase poeple usually get it fixed; that's stock of course. As far as the O2 sensor, it won't hurt it. All it's function in life is to sample the oxygen in the exhaust stream. The internal membranes are pretty stout until you drop one.


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## bedes (Nov 1, 2001)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

Currently, I have this code, among many others.







I have the TT CAT and the code is re-ocurring every 2-3 days. Is anybody getting misfire codes with this code also?
Im interested in the exhaust leak idea because my exhaust has gotten louder and I was thinking to myself that I might have a leak somewhere.







Only one way to find out I guess...
Jesse


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## bedes (Nov 1, 2001)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (bedes)*

Ok guys..
I just got back from the muffler shop. Had them look for leaks and they couldnt find any....their exact words were, "You have a solid system here." haha. So atleast for me an exhaust leak is not the problem.
Anyways, back to solving the problem. What data-blocks would one log to check for problems? I can do the data-logging if someone wants to tell me what blocks to log. 
Jesse


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## 20V1.8Tnut (Dec 31, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (bedes)*

bump


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## genxguy (May 26, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

Just got this a wk ago, after 10months of no problems with GHL 2.5" DP. cleared it earlier today, gonna see if it comes back. if it does, i'll check out the O2 sensor.


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## syktek (Nov 23, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (genxguy)*

I had thrown this code with my GHL and my ATP...


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## 1.8Tango (Apr 18, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

I only got this after I got my 3" dp and ONLY after I put race gas in the tank. 
Doesn't happen all the time though and does go away after I start putting 93 back thru it.


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## Jeff'sGTIAWW (Jun 11, 2003)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (1.8Tango)*

I have this exact same problem w/ my APR downpipe/cat. I got it a few weeks ago and have had a check engine light since 3 days after i put it on (cat. below efficiency threshold) and it has been checked by 2 shops and both say the exhaust has no leaks. But i also have a slight ticking sound only under load, never when reving, that may have something to do with causing this problem


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## RABIDRABBIT1983 (May 13, 2003)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (Jeff'sGTIAWW)*

3" chris green DP/cat No CEL ever.......http://www.unforgettablesnp.com/
2003 awp GIAC


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## Schwagger (Jun 4, 2003)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (RABIDRABBIT1983)*

I hve never thrown a code with my tt turbo back. Hope I never do.


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## genxguy (May 26, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (genxguy)*

cleared my code with a VAGCOM, hasn't come back in a week.


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## Jeff'sGTIAWW (Jun 11, 2003)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (genxguy)*

i've been clearing mine w/ vag-com but it always comes back, i disconnected the battery for 30min. and after i reattached the negative it hasn't come back in almost a week (usually 3hrs. w/ vag.com.)


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## [email protected] (Jun 5, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (Jeff'sGTIAWW)*

I could have sworn there were other ATP owners who had thrown the code, but looks like none voted here. http://****************.com/smile/emthup.gif I wouldn't hesitate to get another ATP cat for my current application.


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## FrankiEBoneZ (Jun 4, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... ([email protected])*

I got this code after about 6-7 months of owning my GHL, no loss in performance though.


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## heysuperman (Aug 17, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

i put this up earlier this year. eurosport came up with a fix
http://forums.vwvortex.com/zerothread?id=766215
where is your pre-cat O2 sensor bung located?


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## [email protected] (Jun 5, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (heysuperman)*

ATP has theirs located here:


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## heysuperman (Aug 17, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... ([email protected])*

i believe that's the problem. the O2 bung on the stock downpipe is on the neck, not next to the cat. most of these people throwing these codes i suspect have that bung next to the cat.


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## [email protected] (Jun 5, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (heysuperman)*

No, that's the REAR O2 sensor. The front is here in the ATP DP:








FWIW, ATP seems to have the fewest (none in this survey) problems with that code.


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## heysuperman (Aug 17, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... ([email protected])*

yeah, mine's up on the neck now. it use to be next to the cat which caused 2 codes


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## Gatorfreak (Jan 14, 2001)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (Cypher2k)*


_Quote, originally posted by *Cypher2k* »_
Mine is cause by cruising below 2500 rpm for too long with a 3" HF cat.


Same here. I never get this code unless I drive like a grandma.


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## heysuperman (Aug 17, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (Gatorfreak)*


_Quote, originally posted by *Gatorfreak* »_
Same here. I never get this code unless I drive like a grandma.

personally i think that's crazy. people were saying that in my thread about the ES 2.5" DP. i'm thinking why would i buy a mod that would only work if i had to drive it hard everyday?


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## linh55 (Jul 25, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (heysuperman)*

3" GHL DP - 4000 miles no CEL


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## MRP2001GTi (Oct 6, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (heysuperman)*


_Quote, originally posted by *heysuperman* »_yeah, mine's up on the neck now. it use to be next to the cat which caused 2 codes


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## heysuperman (Aug 17, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (MRP2001GTi)*

it's been updated. eurosport should now be making DP with the O2 bung on the neck of the DP.


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## 20V1.8Tnut (Dec 31, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (heysuperman)*


_Quote, originally posted by *heysuperman* »_it's been updated. eurosport should now be making DP with the O2 bung on the neck of the DP.

TT DP and FM that I had both have the front O2 sensor port at the factory location, which did not stop them from throwing the CEL.


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## heysuperman (Aug 17, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

which cell did you throw? and how many others with this DP throw a CEL?


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## 20V1.8Tnut (Dec 31, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (heysuperman)*


_Quote, originally posted by *heysuperman* »_which cell did you throw? and how many others with this DP throw a CEL?

"efficiency below threshold"
See my poll above for see how many others wanted to vote.


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## Volksjager (Sep 10, 2003)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

i understand. use to throw 2 codes because if the DP. one was this and the other was O2. after the O2 dung was moved and codes cleared all is well. it is possible that you have a bad cat since there is no such thing as zero defect in manufacturing.


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## heysuperman (Aug 17, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (Volksjager)*


_Quote, originally posted by *Volksjager* »_i understand. use to throw 2 codes because if the DP. one was this and the other was O2. after the O2 dung was moved and codes cleared all is well. it is possible that you have a bad cat since there is no such thing as zero defect in manufacturing. 

http://****************.com/smile/emthup.gif what i meant. just forgot to say it


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## feuerdog (Feb 11, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (heysuperman)*

Ok,...i'm a bit late to this thread, but i'll add my .02.
APR DPP (Stock, 93, 100)
GHL 3" TB
CEL = everyday
It didn't start throwing codes daily until recently(last month), bu the same code keeps popping up.
1. I'll check the exhaust for leaks, and/or reseal the joints.
2. I'll check and clean/replace the O2 sensors if needed.
3. ......????
If this doesn't work, then what? Do I need to move the first O2 sensor bung closer up the DP?
Should I install an O2 sensor "reapeater/clone" in the second O2 bung?
I'm not worried about the engine not working right,.....but that CEL is irritating as he ll.


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## grateful1 (Jul 10, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (feuerdog)*

No choice for GHL and no codes? I am at about 2 months, with about 2000 miles, no cels yet.


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## JoeJetta1.8T (Mar 22, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (grateful1)*

It seems absolutely rediculous that an aftermarket company can sit there and tout a product as being so great, and then have intermittent CEL's from numerous vehicles with their product(s). 
I think the aftermarket companies should just include these lame ass things in the box with the DP/CAT's, and make it the customer's choice as to whether he/she wants to use them.
http://www.mileliminators.com


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## colin007 (Feb 14, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (JoeJetta1.8T)*

i had my milltek turboback for several months before my CEL came on (same code as all of you) and my bunghole








is on the neck of the downpipe also.
if i get it cleared it comes back w/in 3-4 days...


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## evilpat (Feb 26, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (colin007)*


_Quote, originally posted by *colin007* »_i had my milltek turboback for several months before my CEL came on (same code as all of you) and my bunghole







is on the neck of the downpipe also.
if i get it cleared it comes back w/in 3-4 days...

Hmm . . . so the $600+ Miltek DP does exempt you from this problem. Bloody Bosch ECUs . . .


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## feuerdog (Feb 11, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (JoeJetta1.8T)*

It's been said before,......they retaillers aren't responsible for everything that you do to your car.
There is no way they can test all of the possible different configurations of parts and pieces, and driving conditions.
My GHL never threw a code when I was stock programmed, and i'm sure that my APR programming wouldn't throw a CEL if I had the GHL 3" TB,.....but in combination together,....well, it happens.
I don't, and can't, hold either one of them responsible for _my_ alterations to the car.
At least I know what the problem is, and don't have to worry about it being any more than an irritating situation.
The search for the solution continues.


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## slugII (Apr 5, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (feuerdog)*


_Quote, originally posted by *feuerdog* »_It's been said before,......they retaillers aren't responsible for everything that you do to your car.
There is no way they can test all of the possible different configurations of parts and pieces, and driving conditions.
My GHL never threw a code when I was stock programmed, and i'm sure that my APR programming wouldn't throw a CEL if I had the GHL 3" TB,.....but in combination together,....well, it happens.
I don't, and can't, hold either one of them responsible for _my_ alterations to the car.
At least I know what the problem is, and don't have to worry about it being any more than an irritating situation.
The search for the solution continues. 


Sorry man but that doesn't fly.
When a company like APR sells a chip and also a dp as an upgrade refered to as stage 1+, they should work in together without a CEL.
The dp is clearly understood by tuners to be the next step to a chip.


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## Dr. Edlocks (Mar 8, 2001)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

GHL 2.5" DP/cat. CEL since 2nd week of ownership. Performance is great, but not at all thrilled with a constant CEL that may cause me to fail inspection when the time comes. I mentioned this to Jeff at GHL in an IM quite some time ago, but nothing ever came of it.








It would be nice if the fix is something simple like 02 sensor placement needing to change. Then GHL could offer a trade-in for a revised DP/cat. (hint, hint







) Of all the companies out there I bet they'd do it first without even blinking. http://****************.com/smile/emthup.gif


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## feuerdog (Feb 11, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (slugII)*


_Quote, originally posted by *slugII* »_
Sorry man but that doesn't fly.
When a company like APR sells a chip and also a dp as an upgrade refered to as stage 1+, they should work in together without a CEL.
The dp is clearly understood by tuners to be the next step to a chip.

Just because the parts work, and fit, and provide more power, doesn't mean that the car is designed to be able to compensate for the changes.
Tuners are as competitive as we are, except they have to make money. If people buy the stuff then tuners will provide it.
If you throw codes, then that's YOUR problem, not thiers. 
ECU tuning is a seperate matter. But like I said, there is no freekin way that a tuner can possibly forsee the multide of individual configurations of mods on a car.
I have never read anything documented that guarantees otherwise.

Just because you wear a bulletproof vest, doesn't make you bulletproof.


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## slugII (Apr 5, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (feuerdog)*


_Quote, originally posted by *feuerdog* »_
Just because the parts work, 

To many getting a CEL does not constitute a part working properly.


feuerdog said:


> If you throw codes, then that's YOUR problem, not their's.
> I have never read anything documented that guarantees otherwise.
> QUOTE]
> This is a "buyer beware attitude" and although this type of attitude does occur in business it is not considered generally ethical.
> ...


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## [email protected] (Jun 5, 2002)

My personal feeling is that companies selling performance parts should disclose any known problems or faults that may occur. It's not necessarily good advertising, showing your limitations, but it does show honesty on the part of the vendor. Now, if the vendor has never encountered the problem themselves, and customers have not given them feedback, there is no way to know the problem is real. So, the customer's first responsibility is to contact the vendor to let them know they found the problem, then if the customer wants to post the problem on forums, newsgroups, etc. it is their choice. But, it isn't fair to the vendor to have their first notification of a problem be a post on VWVortex or elsewhere.
Just to show I am not taking a "Do as I say not as I do attitude", here are the known problems with VAG-COM:
http://www.ross-tech.com/vag-com/issues.html


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## SlvrBllt (Oct 15, 2001)

*Re: ([email protected])*


_Quote, originally posted by *[email protected]* »_My personal feeling is that companies selling performance parts should disclose any known problems or faults that may occur. It's not necessarily good advertising, showing your limitations, but it does show honesty on the part of the vendor. 


Just for the record, I was told _prior_ to purchasing my DP that it would cause a soft code, but NOT a CEL.


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## trbochrgm02 (Dec 11, 2002)

*Re: (SlvrBllt)*

I have a 3"ATP with the 3" cat and my CEL has been on since the first day I put it on


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## feuerdog (Feb 11, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (slugII)*

I was told by GHL when I ordered my exhaust that it would not throw codes on my car the way it was when I ordered the part(s).
And it didn't.
I was told by APR that the programming _might_ not throw codes, but it depended on the car and the other parts installed,.......I accepted that as reasonable because of the ability to erase codes with the APR programming.
I don't, and can't, and won't blame them for the mods that _I_ did to my car.
You have to assume some responsibilty on your own part as to what you add and are going to tolerate as far as the products that you add to your car. The manufacturer is and can only be responsible for the installation and product use based on a certain point of reference,....ie; a stock or slightly modified car of a particular type.
I don't see how I can hold them solely responsible,.....or even partially,...it doesn't make sense.








I took the chance of mixing parts, I assumed that reponsibilty.
Many parts are designed to work together because of STANDARDS in the industry:
Wipers, tires, glass, paint, shocks, coils, oils, seatbelts, etc.
All of these parts are manufactured with a standard of compatibility in mind. Some are relatable components, some are not. 
But in an engine situation there are far many more variables to deal with. The OBD system, in intake capacity, the exhaust restriction, the fuel quality, the plugs, the sensors, the ECU, the turbo, etc.,.....it can all be changed. How in the FRIGG do expect a maker to anticipate all of the possible configuarations? There's no way.








Why do think VW voids warantees when you start modifiyng major parts?








The Vag Com gurus have an excellent system going, sure, and an open discussion of features and troubleshooting,.......great.
Call GHL and you will be treated to some of the best customer service on the planet(the best I have ever experienced).
Even APR, with all of the nightmare situations it dealt with at Waterfest 2003, has some really good service.
And no, I am not a manufacturer or even a vendor.
If you have problems, return the part, by all means go ahead. I'm just sharing my opinion like everyone else.
A'd like to diagnose then problem first, and see if I can troubleshoot the issue here,......and if I can't, THEN i'll go to the manufacturer and see if they can be any help. But even then, I won't hold them responsible unless it has to do with the quality and munction of the part itself,.......compatibility with modified systems is another subject.
That's all I gotta say.


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## Mk418TDUB (Jun 10, 2003)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (feuerdog)*

My APR just started to thorw this code at the beginning of the week....i clear it with APR FCE and it pops back up i start the car back up and drive for a little while














Ive just stopped wasting my time clearing it http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif


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## colin007 (Feb 14, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (Mk418TDUB)*

does this code mean that there is any performance loss?


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## feuerdog (Feb 11, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (colin007)*

No,...not really.
We understand basically _why_ it is happening, it's just that it's annoying.
It won't directly affect power output to my knowledge, unless the ECU is trying to compensate for the Cat not working right







,...which wouldn't make sense. 
(But who knows for sure







)


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## UVAJetta (Mar 14, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (feuerdog)*

What about if you don't have an aftermarket DP/cat and also have a VR6 engine with stock exhaust and you get this code. 
I am hoping it is exhaust leakage, otherwise, I am at a loss.


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## 4string (Sep 26, 2001)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

I have Revo software and a GHL 2.5" downpipe and got a softcode for 'Cat efficiency below threshold', only once no MIL but it stored the code as intermittent. I know what caused it was letting my car warm up for 15 minutes in 15 degree F temp in the morning. Letting the engine idle for long periods of time can possibly generate this code when it is cold outside. Lately in the morning (it's been 10-20 degees F lately) I get in the car and just go......no DTC's as of yet. Just crank up the heated seats.


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## UVAJetta (Mar 14, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (4string)*

Mine takes about 40 min of driving to come on. Do mostly highway driving so I must have a bad cat or sensor. Car doesn't sound louder. Not primary driver so can't figure out other patterns.


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## UVAJetta (Mar 14, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (UVAJetta)*

It was my Cat afterall. Ran the tests with the VAG-Com. I am over 80K miles so it is up to me to fix it. Figures!


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## not_too_shabby (Apr 30, 2001)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (UVAJetta)*

so what's going to happen when you guys go in for emmissions testing. Many states are scanning obd-II ports for codes instead of doing the dyno testing. You can't just clear your code before you drive up because you readiness codes will not be set. This will be a big problem in a couple years after everybodies new car exemptions run out.


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## 9VW23yrs (Jun 22, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (not_too_shabby)*

This is the solution ....








our cars need a California OBDII compliant cat...
All the current aftermarket cats are old EPA standard ...


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## FlashRedGLS1.8T (Apr 17, 2001)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (9VW23yrs)*


_Quote, originally posted by *9VW23yrs* »_This is the solution ....








our cars need a California OBDII compliant cat...
All the current aftermarket cats are old EPA standard ...









Unfortunately.


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## 20V1.8Tnut (Dec 31, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (FlashRedGLS1.8T)*


_Quote, originally posted by *FlashRedGLS1.8T* »_








Unfortunately.

No worky?
Got CEL, or you just can't get it?


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## heysuperman (Aug 17, 2002)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

get some thermal wrap and wrap the cat in it.


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## JettaRed (Aug 14, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

I replaced the rear o2 sensor (for about $22) and it seems to have fixed the problem. I suspect swapping the original o2 sensor over may have damaged it in some way. For the price they are now, it's worth installing new with a new dp--even getting a couple spares!


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## screwball (Dec 11, 2001)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (JettaRed)*

i've had the o2 sensor replaced as well and it didn't affect the two codes i'm throwing.


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## JettaRed (Aug 14, 2000)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (screwball)*


_Quote, originally posted by *screwball* »_i've had the o2 sensor replaced as well and it didn't affect the two codes i'm throwing.

Hmmm. I know of a local tuner who is in the process of developing an o2 modification that will fix this problem. He's not ready for prime time yet, but will be soon. Apparently, this has already been done for BMWs and just needs some modification to work on VWs.
I'm sure he will be posting as soon as he's ready to go on sale. (Hint: Read my signature.)


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## GTIGuy01 (Apr 19, 2001)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (JettaRed)*


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## Holksvagon (Jun 13, 2003)

I have this "Cat below Effeincy threshold" code but at the same time as this is happening I can only spike up to 15 lbs. it seems as though there is a leak somewhere or something restricting the flow.. would a faulty cat cause this... I have an Up chip and usually spike to 21lbs and settle to 16-17.. Now its just a slow rise up to 15 lbs and then nuthin more.... any one?


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## Holksvagon (Jun 13, 2003)

Well just got CAT replaced by VW and POOF all is better now... they said the cat was all clogged up... just some info for ya


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## Uszatek (Sep 4, 2004)

*Re: (Holksvagon)*

Do we have a solution for this problem then people? Espeically APR dp?


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## URO5TYL (Mar 11, 2003)

*Re: (Uszatek)*


_Quote, originally posted by *Uszatek* »_Do we have a solution for this problem then people? Espeically APR dp?


yes do we... i need some help wit my apr dp thats throwing that damn code.. let me know thanks, peace


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## Padlock (Mar 30, 2003)

*Re: (URO5TYL)*

any new info?!


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## feuerdog (Feb 11, 2002)

There is the "spark arrestor/spacer" mod that has been known to fix this issue.

Or, get a higher count/higher efficiency cat(non-high flow).


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## rneedham1979 (Apr 8, 2006)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (20V1.8Tnut)*

my cel cam e on today after i installed a ghl 3" and 2.5 inch cat back a week ago. i reset it at advanced auto but what is the correct fix?


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## RussellsGTI (Sep 2, 2005)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (Cypher2k)*


_Quote, originally posted by *Cypher2k* »_
Mine is cause by cruising below 2500 rpm for too long with a 3" HF cat.



just yesterday, crusin it 2 hour traffic just like 2500rpm and guess what....CEL saying catalyist effiency below threashold.


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## RussellsGTI (Sep 2, 2005)

*Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (RussellsGTI)*

oh and i have a 3'' TB GHL exhaust.


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## 1.8T_CR (Oct 24, 2003)

*Re: (Holksvagon)*

I have the same problem 
Did you fix it?


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## RussellsGTI (Sep 2, 2005)

*Re: (1.8T_CR)*

yeap mine just went away. after all the ice melted and it takes like 3 cold starts and cruszin over a certain mileage to reset the ecu to check if the problem still consists and my cel just went away. some people have to do the O2 spacer mod. search for that there a DIY for that. i just lucked out.


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## RussellsGTI (Sep 2, 2005)

*Re: (1.8T_CR)*


_Quote, originally posted by *1.8T_CR* »_I have the same problem 
Did you fix it?

you can maybe using this mod, or just delete it and see if it comes back.

http://forums.vwvortex.com/zerothread?id=1366095


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## 1.8T_CR (Oct 24, 2003)

*Re: (RussellsGTI)*

I tried but didn't work, still have the problem.
Another idea?


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## JettaGLI18t (Jun 28, 2004)

*Re: (1.8T_CR)*

back from the dead... I just got this today, driving a little slow due to construction... hope thats it.


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## sotiris (Sep 24, 2007)

*Re: (JettaGLI18t)*

when i put the 70mm exchaust and the tubular manifold with 200hjs cat and if i go slow i have this fault
to make me understand ....
this fault is for second sensor......
(the cat and second sensor are not to hot and they don't do their "work" ???)








and the solution is something like this (picture)???????
any other solution.....? 
(must we put the second sensor nearest the cat..?? more temp)











_Modified by sotiris at 10:45 AM 12-16-2007_


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## sotiris (Sep 24, 2007)

*Re: (sotiris)*

today i made this.....








tomorrow i put this and i will report !!!!


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## sotiris (Sep 24, 2007)

*Re: (sotiris)*

4 days / 400 klm slow (because break in the car)
with this "part" i made and nothing yet.......
this is my solution for 16804 fault ........


















































































_Modified by sotiris at 11:51 AM 12-21-2007_


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## Neil_Ireland (Aug 1, 2006)

*Re: (sotiris)*

This is exactly what I'm looking for, I have the same fault code.
What did you make the part from sotiris?
Thanks,
Neil.


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## dj givv (May 20, 2005)

*Re: (Neil_Ireland)*

wow....and to think i was the only one with this problem.








GOOD SOLUTION....i will give it a try


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## BassNotes (Mar 16, 2005)

I used to get a CEL with that code occasionally. It usually popped up at times when I was driving slowly, like in bumper-to-bumper traffic or while cruising around a crowded parking lot looking for an available space. 

Also, the readiness bit for the cat would not set. I tried running the readiness test cycle with VCDS but still only the cat would fail the test. 

Replacing the cat/DP with one from a low-mileage 1.8T solved the problem--readiness passed and no more CEL--and allowed my car to pass its biannual smog check easily.


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## gurupprasad (Mar 16, 2016)

*16804in my Octavia vRS 2005*

Hi,

I had a couple of fault codes in my 2005 Skoda Octavia vRS with respect to O2 Sensor.

on a suggestion from my mechanic, i removed the catalytic convertor. still the fault codes were recorded.

After a few trial & Errors, i did order a new O2 Sensor from EBay and the fault codes were gone.

after driving for about 100 kms (i Live in India), the CEL came up and VCDS pointed out to 16804.

my question here is

Is this Fault a result of me removing the Cat-Con?
do i have to do any ECU Coding to let the system know that i have removed the Cat-Con?
Will Fitting a Spacer for O2 Sensor Bank1 - Sensor1 solve this Issue?
Is this issue due to the second O2 Sensor? (I don't see any fault codes related to that)

Kindly help me in identifying the root cause so that i can solve this issue.

along with 16804, a few other codes were also recorded. - 17705 & 18074

Thanks in Advance.

Regards,
Gurupprasad B


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## Kemrick (Jun 5, 2020)

Audi tech said:


> *Re: Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has thi ... (dbrowne1)*
> 
> Cat efficencly below threshold is usually an exhaust leak by the post O2 sensor, and it's usually at the clamp that connects the down pipe to the rest of the exhaust. If there is even a small leak, then under deacceleration there is a pressure gradient that is created. And, then the air outside is then "sucked" back in to the exhaust system for a split second.


Coud that be why I continue to get the 420 code, below threshold, even after replacing the downstream O2 sensor, the upstream O2 sensor, and the cat? Everything seems as tight as it can be, how are you testing the connection for a leak?


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## Vegeta Gti (Feb 13, 2003)

Your software isn't properly setup for it, so you should try an O2 spacer.

Sent from my SM-N975U using Tapatalk


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