Catalyst System; Bank 1: Efficiency Below Threshold/ DIAGNOSTICATOR + OLD GUY help:(

[Antekaudi]

About 25-30k miles ago i had this code "16804: which is Catalyst System; Bank 1: Efficiency Below Threshold.

I have diagnosed the problem and it turned out to be fuel filter. I put new fuel filter and the car came to life and code disappeared.

About 5k miles ago i got the code again. I have inspected the exhaust system for any leaks and intake system but couldnt find anything. I also changed air-filter to high flow AFE filter.

My car is 2005 1.8t 6spd with 60k miles.
Code comes back every 60-100 miles and check engine light goes on and stays on.

Thanks for help.

[spyder101]

You need a new cat conv.

[JoshDub]

You need to replace the cat. Or you could buy a HFC or a test pipe.

[Antekaudi]

How do you know its a cat ?

Like i said i had this code before and the other time it turned out to be fuel filter.

If it is cat, is it something thats covered in CT under emissions law ?

Thanks

[JoshDub]

Well if the cat is bad you have a federal warrenty of of 80,000 miles and something like 8 years.

[Antekaudi]

Is there any way to check if it cat ? I have vag-com if that helps.

[A4.Rob]

yeah po420 is the Catalyst System; Bank 1: Efficiency Below Threshold code

thats what i had (issue is bad catalytic converter 100%) I got a used cat from here from a user for about $100. Got that installed, cel is gone and its good as new.

[Antekaudi]

Kind of weird for cat to fail at 60k miles ? Also would i have to pay anything for dealer to diagnose this problem ?
Also my car has salvage title would that affect the federal warranty ?

[A4.Rob]

Yeah that is strange. Mine failed just over the warranty at around 85k, so Audi wouldn't do anything for me. Since your at 60k and with in the warranty, I'm pretty sure that everything will be free regarding it even the diagnose. But if its not a cat issue they might make you pay, I'm not sure. I'd say best bet is to call the dealer tomorrow, tell them the situation and see what they say. If they give you any weird info, call AOA.

I dunno about the salvage title affecting it.

[spyder101]

Kind of weird for cat to fail at 60k miles ? Also would i have to pay anything for dealer to diagnose this problem ?
Also my car has salvage title would that affect the federal warranty ?

No, it's common. yes, you will have to pay diagnosis. Dont' know about the salvage title situation.

[Antekaudi]

Interesting, will call audi tmr.


I still wanna find out how to further diagnose this issue myself. I hve vag-com so i can take some readings for you guys.

[A4.Rob]

Interesting, will call audi tmr.


I still wanna find out how to further diagnose this issue myself. I hve vag-com so i can take some readings for you guys.

that code means faulty cat. I dont think you need to diagnose it any more.

[Antekaudi]

Last time i thought its a bad cat too and that was when my car had 30k miles, it was fuel filter. Anyone knows why fuel filter would affect that ?

[Gmoney]

My cat went at about 60k. Audi diagnosed it for free but I had to go twice. Basically they just had to read the code and then clear it and if it came back then it was bad. It was covered under the federal 80k or 8 years warranty.

[A4.Rob]

Last time i thought its a bad cat too and that was when my car had 30k miles, it was fuel filter. Anyone knows why fuel filter would affect that ?

um it obviously wasn't the fuel filter if the code came back........


also sometimes when cats are failing they can be intermittent and the cel will go off and on untill it finally fails which it probably has now.

[Antekaudi]

Interesting, kind of weird that code went away for 30k miles and cat failed at 30k. My car has 60k right now. I will call dealer tmr and see what they say.

My car had bad coilpack once and i drove it for few miles, maybe thats what killed the cat.

[Audituning02]

I have 116k on the clock and the same thing going on. I get a MIL and read the code its a p0420 which is cat efficiency below threshhold. I too cleared the code and it comes back about every 100 miles or so, sometimes more sometimes less. I unplugged the first o2 sensor ahead of the cat and ran a meter through it to check the efficiency. It came back that there was no restriction. Indicating the cat is still intact, yet I still have the code so I believe the cat flow meter to be inaccurrate and I am quite confident I need to replace the cat soon.

[old guy]

It isn't all that unusual to get a P0420 and have it go away after a few hot/cold drive cycles. Cat monitoring isn't a continuous process. The ECU performs a diagnostic at different intervals depending upon certain conditions in the drive cycle and if the efficiency is out of range you get a CEL. If the catalytic converter passes several subsequent test cycles the ECU will turn the CEL off. As the cat deteriorates the CEL will present itself more often until it just stays on all the time. If you are under 80K miles/8 years it should be covered under a federally mandated emissions warranty.

[diagnosticator]

Besides a failing cat, the DTC can also be caused by a bad post O2 sensor, However, a second DTC for the sensor itself usually is set when that is the issue, but not always.

[Antekaudi]

The post o2 sensor is the one after the cat right ?

When i first got the code when my car had about 30k miles i replaced that o2 sensor thinking it was it. But it wasnt, and i still cant explain why fuel filter replacement fixed the issue for 30k miles. Could be something with the connection to ecu ? Because of all the humid etc?

any other ideas ?

[old guy]

The post o2 sensor is the one after the cat right ?

When i first got the code when my car had about 30k miles i replaced that o2 sensor thinking it was it. But it wasnt, and i still cant explain why fuel filter replacement fixed the issue for 30k miles. Could be something with the connection to ecu ? Because of all the humid etc?

any other ideas ?

That is correct, the post O2 sensor is the one on the outflow end of the cat. As I mentioned earlier the ECU runs a diagnostic test on the cat at different intervals under different conditions. It's very possible that your clogged fuel filter was causing your car to lean out and consequently the rear sensor didn't see what it expected to see on one of its diagnostic checks and threw the P0420. As long as the cat passed the next several diagnostic tests the ECU turned off the CEL. Your issue now is probably a deteriorating cat.

[widgget]

will a o2 spacer resolve the CEL?

[old guy]

will a o2 spacer resolve the CEL?

Sometimes it will sometimes it won't. Just have to try it and see. However, if the OP is under 80k miles he should see about getting it covered under warranty.

[widgget]

i asked because i just started seeing this after replacing the rear O2 sensor on my 5spd. it's over 80k so i'm trying to find a cheap way out and it needs to be inspected by the 23rd.
guess i'll give the spacer a try.

thought about swapping the HFC from the tiptronic for a few days to get the inspection done but thats allot of work and it might still throw a CEL (doesn't on the tiptoninic but isn't that written out in Revo S3 sofwtare?)

[bigdadi]

i asked because i just started seeing this after replacing the rear O2 sensor on my 5spd. it's over 80k so i'm trying to find a cheap way out and it needs to be inspected by the 23rd.
guess i'll give the spacer a try.

thought about swapping the HFC from the tiptronic for a few days to get the inspection done but thats allot of work and it might still throw a CEL (doesn't on the tiptoninic but isn't that written out in Revo S3 sofwtare?)

Istall a Mini cat cel fix betweem post O2 sensor and the CAT may stop the cel light. The post O2 sensor won't see HC & NOx so it won't throw a code.
www.bigdaddiesgarage.com
This won't fix O2 sensor though if sensor is bad. The sensor has to be on woring condition.

[kt883]

it was likely never the fuel filter but that probably improved the performance a bit and you deleted the codes so the cat code only comes sporadically. I think your holding to much value to that notion that the fuel filter is the problem.

[blownb6]

it was likely never the fuel filter but that probably improved the performance a bit and you deleted the codes so the cat code only comes sporadically. I think your holding to much value to that notion that the fuel filter is the problem.

4 yrs late

[Antekaudi]

Sweet necro-bump.

Anyways, the issue was the catalytic converter itself. I ended up putting 034 HFC.

The stock cat separated inside and was moving around, one time it would line up in and not throw a code and others it would fall out of place and throw a code.

The car has now 140k miles and never been better :)

[Knives1010]

Nice to have a resolution to the problem at least

[customa4]

That's awesome that the OP replied 4 years later! Props to you OP and like Knives said, it's good to have a resolution.

[SlickFix]

Props? Hell, the OP should be tarred and feathered and run out of town on a rail for making us wait 4 years to find out the resolution!

[Knives1010]

Argh if you think that then I'm scared to see what you would do to an OP who doesn't post a resolution


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