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Discussion Starter · #1 ·
I know this problem is well covered in the forums. I'm a new member as well as a new owner. The info on this site is incredible. I'v already completed a couple projects with info from the forums.

I need to replace my cat. I'm getting the code 16804 "bank 1 efficiency below threshold". Most of the aftermarket cats I've seen have a bung for the O2 sensor in the cat. I've noticed mine has an O2 sensor before and after the cat.

I have already called VW and mine is out of warranty and I was planning on replacing the rear O2 sensor to see if that was the problem first. (all this thanks to info I found on the forums)

My Questions are... Am I looking at the wrong part or will these work and I just have to relocate the sensor? If sensor relocation, which one, front or rear?

If anyone can give me some advice, point me to the correct thread or correct part I would appreciate it. I've been looking for days, just can't seem to find the right info.

2004 GLS convertible, 6 speed triptronic, engine 2.0 code BGD.

Thanks!
 

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This diagram shows the front O2 sensor being mounted to the exhaust manifold:

Volkswagen Workshop Manuals > New Beetle L4-2.0L (BEV) (2004) > Engine, Cooling and Exhaust > Exhaust System > Exhaust Pipe > Component Information > Service and Repair > Page 2917

This is the way my AEG is: front O2 in the manifold, rear O2 is behind the catalytic converter. Are you sure that there are 2 mounted to the exhaust pipe?

The rear O2 sensors almost never fail. The only reason would be if it has been contaminated by bad gas or something. It is only used to check emissions, not to set mixture or anything.
 

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Discussion Starter · #3 ·
You're correct. There is one on the manifold and one after the cat. I guess I was just brain fried or something.

Thanks for the diagram.

Any suggestions on a good after market cat?
 

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Discussion Starter · #5 ·
Thanks.

I was thinking about dropping it out and having a welder friend of mine just cut out and replace the actual cat using the old down pipe. Do you know if people have problems with that flexible part in the down pipe with leaks?

Just trying to shave dollars where I can. This thing is a drive-able project right now. Seems like I have a laundry list and I've only had it about a month.
 
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