# 16804 - Catalyst System; Bank 1: Efficiency Below Threshold



## cdotter (Apr 26, 2010)

After noticing a CEL I scanned my '03 Audi A4 1.8T and came up with this:



> Address 01: Engine Labels: 06B-909-518-AMB.lbl
> Part No SW: 8E0 909 518 AF HW: 8E0 909 018 A
> Component: 1.8L R4/5VT G 0003
> Coding: 0016701
> ...


Ross-tech wiki says it could be a lot of things, mainly O2 sensors or the catalytic converter. I don't want to spend blindly and hopefully nail the problem. Does anyone know of a test I could do (readiness test?) to pinpoint the problem?

I noticed this, too:



> Readiness Status: 0110 1101
> Exhaust Gas Recirculation: Passed
> Oxygen Sensor Heating: Failed or Incomplete
> Oxygen Sensor(s): Failed or Incomplete
> ...


I'm guessing they're all "incomplete" because everything failing at once seems highly improbable.


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## [email protected] Parts (Nov 27, 2006)

Hey sweetie,

Please post a full auto-scan.

Looks to me like I bet I could help you with a firmware update to correct that vs a new CAT.

bye bye,


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## cdotter (Apr 26, 2010)

> Thursday,22,September,2011,18:52:45:47483
> VCDS Version: Release 10.6.4
> Data version: 20110418
> 
> ...


.


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## [email protected] Parts (Nov 27, 2006)

Super thanks for the auto-scan handsome.

Yeah you need a firmware update for sure before spending big buckaroo's on that CAT.


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## gypsydoctor (Mar 26, 2009)

*My code 16804 was caused by an exhaust leak*

I was getting code 16804 - Catalyst System; Bank 1: Efficiency Below Threshold. The Cat and O2 sensors were replaced 5 months ago. It turned out the problem was an exhaust leak at the rear of the Catalytic Converter. Tightening the clamp fixed the code and let me pass the readiness test.

(VAG-COM Basic Settings Block 46 improved from 0.71 to 0.46 (


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## [email protected] Parts (Nov 27, 2006)

Why hello Dr. Kill patient,

Sweets, please don't practice here without an auto-scan.

Your information while being half correct is understood as being helpful but is in fact misleading.

I hope your real diagnosis's are not so half ass-ed.

Bye bye


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## nosborn94 (Feb 7, 2010)

Was this issue resolved?


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## cdotter (Apr 26, 2010)

nosborn94 said:


> Was this issue resolved?


I'm 99% sure it's the catalytic converter because I smell a burnt clutch type smell every now and then when I come to a stop, which is consistent with a bad cat.

A new OEM cat is $800+ and aftermarket cats are $300. I'm going to get a universal Magnaflow cat insert and make my own cat for a few hundred dollars. I'm replacing the rear O2 sensor while I'm at it.


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## cdotter (Apr 26, 2010)

In case you're wondering, I'm guessing a bad camshaft position sensor killed my cat.

Over the past few days my car has been a pain in the ass to start. Sometimes it starts right away but other times it requires 3 or 4 tries. I scanned for codes and found this:
16727 - Camshaft Position Sensor (G40): Signal too High 
P0343 - 001 - Upper Limit Exceeded - MIL ON

I googled a bit and symptoms for a bad camshaft sensor are hard starting (check), rpm hunting/surging (check, started happening with the hard start), rough idle (check, I thought this was a normal thing because my car has had a vibrating idle for the past year), and occasional misfires (check, I can feel my car 'miss' maybe once a minute and VAGCOM will show a random misfire every now and then, although it's not nearly enough to throw a check engine light.)

I can definitely smell raw fuel during the hard-starts and I vaguely remember smelling raw fuel over the past year to year and a half, so I'm guessing all of this rough idling, misfiring, and hard starting is dumping too much fuel into the cylinders and burning up my catalytic converter.

Anyway, I have a new rear o2 sensor, a universal catalytic converter, and a new camshaft position sensor in the mail. I'll let you know in a few weeks if it fixes everything.


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## nosborn94 (Feb 7, 2010)

cdotter said:


> In case you're wondering, I'm guessing a bad camshaft position sensor killed my cat.
> 
> Over the past few days my car has been a pain in the ass to start. Sometimes it starts right away but other times it requires 3 or 4 tries. I scanned for codes and found this:
> 16727 - Camshaft Position Sensor (G40): Signal too High
> ...


Ok. I had a bad crankshaft sensor and coolant temp sensor at the same time I got 16804. May have had a similar issue even though it was my crankshaft and not camshaft sensor. I had got 17521 (pre-cat 02 sensor) once a couple months ago when this started so I may replace that as well. 

I've checked my MAF and it looks fine. Im pretty its the Cat and am leaning towards that as well.

Not sure if you ordered already, but I found this Magnaflow on Amazon (~$200 free shipping). This model # fits many MK$ Cats:

http://www.amazon.com/Magnaflow-46035-Universal-Catalytic-Converter/dp/accessories/B000ED2RYU


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## cdotter (Apr 26, 2010)

nosborn94 said:


> Ok. I had a bad crankshaft sensor and coolant temp sensor at the same time I got 16804. May have had a similar issue even though it was my crankshaft and not camshaft sensor. I had got 17521 (pre-cat 02 sensor) once a couple months ago when this started so I may replace that as well.
> 
> I've checked my MAF and it looks fine. Im pretty its the Cat and am leaning towards that as well.
> 
> ...


Actually, I just decided to get a used OEM cat. I had my dad (who welds) look at the cat, and he doesn't think he can make it fit because it has a 45 degree kink in the middle. VW 1.8t cats must be a bit different than Audi 1.8t cats because of the transverse vs longitudinal layout.


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## stan067 (Feb 25, 2010)

As Jack said you need a firmware update to the ECU. AMB motors known for this and as Jack said there is an update for the ECU software. Either get with Jack to send your ECU or try the dealer for the software update. Good Luck


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## cdotter (Apr 26, 2010)

stan067 said:


> As Jack said you need a firmware update to the ECU. AMB motors known for this and as Jack said there is an update for the ECU software. Either get with Jack to send your ECU or try the dealer for the software update. Good Luck


I know that the catalytic converter is on its way out. I can smell it burning and, at times, I can hear it rattling. I don't see how it's a firmware issue when this problem never happened in the previous 8 years of ownership. I'll see how a "new" catalytic converter and o2 sensor fixes it before I let Audi charge me hundreds of dollars for a firmware update.

edit: And please don't take this the wrong way, as me ignoring my suggestions. I just think that the problem is the catalytic converter because, like I said, I can smell and hear it dying.


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## stan067 (Feb 25, 2010)

No problem. Update is for a good cat that throws this code. If you know the cats bad change it. Good luck


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## [email protected] Parts (Nov 27, 2006)

Hey Stan Lee Marvel Comics,

Happy New Year!

:::::ALERT FORUM ACTION EMERGENCY MESSAGE:::::

THIS POST MOVED/VACATED BY JACK TO PROTECT CONTENT FALLING INTO THE GAPING HOLE OF THE VORTEX

IT SEEMS NO GOOD DEED GOES UNPUNISHED!

http://www.youtube.com/watch?v=HaoySOGlZ_U 

Just email or PM John [email protected] as to why I have chosen to do this for a modification answer to these posts.....
Ultimately this is his fault for how the account was handled.
[email protected]
You could say I feel insulted and abused..........


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## cdotter (Apr 26, 2010)

Got the "new" catalytic converter installed with a brand new rear O2 sensor. Throttle response off idle is much better and the idle has smoothed out considerably. I'm guessing the old one was plugged up. The check engine light is off for now, after a 15 mile drive. I'll let you guys know if the light is still out come Saturday. By then I should have about 400 miles on it.


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## [email protected] Parts (Nov 27, 2006)

:::::ALERT FORUM ACTION EMERGENCY MESSAGE:::::

THIS POST MOVED/VACATED BY JACK TO PROTECT CONTENT FALLING INTO THE GAPING HOLE OF THE VORTEX

IT SEEMS NO GOOD DEED GOES UNPUNISHED!

http://www.youtube.com/watch?v=HaoySOGlZ_U 

Just email or PM John [email protected] as to why I have chosen to do this for a modification answer to these posts.....
Ultimately this is his fault for how the account was handled.
[email protected]
You could say I feel insulted and abused..........


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## nosborn94 (Feb 7, 2010)

cdotter said:


> Got the "new" catalytic converter installed with a brand new rear O2 sensor. Throttle response off idle is much better and the idle has smoothed out considerably. I'm guessing the old one was plugged up. The check engine light is off for now, after a 15 mile drive. I'll let you guys know if the light is still out come Saturday. By then I should have about 400 miles on it.


I agree. Do the test in basic settings. block 36, 34, then 46. Here's the link for quick reference:

http://forums.vwvortex.com/showthread.php?1265064


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## stan067 (Feb 25, 2010)

I also agree do the readiness tests. Was it an aftermarket cat and of what type? A lot of aftermarket cats don't pass the tests so run the tests. I still want to know if your local dealer will even do the update. Good Luck


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## [email protected] Parts (Nov 27, 2006)

:::::ALERT FORUM ACTION EMERGENCY MESSAGE:::::

THIS POST MOVED/VACATED BY JACK TO PROTECT CONTENT FALLING INTO THE GAPING HOLE OF THE VORTEX

IT SEEMS NO GOOD DEED GOES UNPUNISHED!

http://www.youtube.com/watch?v=HaoySOGlZ_U 

Just email or PM John [email protected] as to why I have chosen to do this for a modification answer to these posts.....
Ultimately this is his fault for how the account was handled.
[email protected]
You could say I feel insulted and abused..........


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## remrem (Jan 20, 2008)

Good morning all,

I see that you are a group of members who are particularly knowledgeable of such things, so I was wondering if you wouldn't mind reading about my current dilemma in my thread in the Vortex Phaeton forum: 


http://forums.vwvortex.com/showthread.php?6909671-Pre-catalytic-converter-issues


Even though it's a W12 engine, I suspect many of the same basic concepts apply, so perhaps you might see some parallels and offer some advice. The main difference being that if you have to replace certain related components in the W12, the entire engine and transmission must be removed! So, thanks very much in advance for any suggestions. I have my Ross Tech VCDS at the ready and am prepared to run any additional tests. 


Thanks very much in advance:


Best regards,
Ron M.
remrem (from the Phaeton forum)


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## jjcsnlynn (Mar 9, 2008)

*Bad Cat??*

I followed the instructions below and when I got to 046 I received the NO OK. Is that a definative BAD CATALYTIC CONVERTER? No chance of the sensor being bad (it passed block 36)?

So, here we go. Car is at operating temperature. And I will assume that you're at least somewhat knowledgeable about the use of the Vag-Com.
1) clear codes
2) reset throttle adaptation (04/060)
3) start engine and let it idle
4) 04/030 and check o2 sensor control. you want to see 111 in field 1 and 110 in field 2
5) 04/107, and click start test. wait until field 4 goes from test off to test on to syst. ok
6) leave basic settings, crack throttle open briefly so RPMs go over 3k
7) back into basic settings, enter 034, start test, press foot on brake while flooring throttle. RPM's will increase to about 2300. Test will begin soon after exhaust gas temperature passes 350 degrees. Test will run, and you should see B1S1 OK.
8) now go to basic setting group 036, start test, at idle, and see if the rear sensor tests ok. you should see B1S2 OK.
9) repeat step 8 in setting group 037
10) group 043, start test, brake and throttle together again, and run test until you see B1S2 OK.
11) and now for the litmus test. go to group 046, brake and throttle together, and run the test. test likely won't start until exhaust gas temp goes over 550. 

If everything checks out except for step 11 above, rest assured that you have a bad cat. I know it looks like a pain in the ***, but all of these tests together literally take about 5-10 minutes to perform.


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