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Discussion Starter · #1 ·
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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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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Discussion Starter · #5 ·
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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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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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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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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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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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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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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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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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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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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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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