CEL- P0420 Catalyst Efficiency Low-Bank

[FPBBrandon]

Hey all

On the drive home from work today, my B6 threw a CEL. I have an 04 1.8TQM USP. Symptoms were very subtle. Mileage dipped a very small amount, and the turbo seems much more eager to spool at lowish RPMs (2000 instead of what typically seems like 2800-3000).

Took it to Autozone and had the code read, and this is the only one it spat out.

Did some searching, and found that this problem is generally one of two things- Bad Catalytic Converter, or Bad 02 Sensor. My reading also suggested that the Cat is warrantied for 8yr/80k by federal emissions warranties.

I suppose my few questions are:

1. Anyone know the likelihood of 02 sensor vs. bad cat?
2. If its an 02 sensor, how much should I expect to get pwned out of at the stealership?
4. What happened to 3?
5. Does anyone know if theres a DIY on the 02 sensor, and if so, am I putting the car at any significant risk while driving with a faulty 02 sensor while I wait for a new one to arrive?

Noob questions, I've got my flame suit on for sure, but at least I searched

What a way to ruin a weekend :(

[B6480Avant]

ive gotten that code once a month for the past 4months but sure enough as soon as i start driving towards the dealership it goes away ive noticed that after like the 5th time i start the car it will go away usually like 3 days the o2 sensor wont do anything too bad just horrible mpg no risk that i know of and the swap is fairly straight forward if you can reach

[HTA A4]

When it happened to me, it was a bad cat. So I went HFC then and now I'm selling it. Test pipe baby!

[B6480Avant]

gtrs a4 : did your cel stay on always? did you take it in to get a new one so you can sell it

[HTA A4]

Yeah I always had a CEL with the HFC because the software I had didn't have an override for the rear o2. But I was out of warranty when I had the bad cat. so I just went high flow! And now the test pipe trumps them all!

[monkey323i]

Hey all

On the drive home from work today, my B6 threw a CEL. I have an 04 1.8TQM USP. Symptoms were very subtle. Mileage dipped a very small amount, and the turbo seems much more eager to spool at lowish RPMs (2000 instead of what typically seems like 2800-3000).

Took it to Autozone and had the code read, and this is the only one it spat out.

Did some searching, and found that this problem is generally one of two things- Bad Catalytic Converter, or Bad 02 Sensor. My reading also suggested that the Cat is warrantied for 8yr/80k by federal emissions warranties.

I suppose my few questions are:

1. Anyone know the likelihood of 02 sensor vs. bad cat?
2. If its an 02 sensor, how much should I expect to get pwned out of at the stealership?
4. What happened to 3?
5. Does anyone know if theres a DIY on the 02 sensor, and if so, am I putting the car at any significant risk while driving with a faulty 02 sensor while I wait for a new one to arrive?

Noob questions, I've got my flame suit on for sure, but at least I searched

What a way to ruin a weekend :(

Scan your codes,
if only P0420 shows up without any other O2 related codes, most likely that your cats out.

Have the stealership to test your O2's voltage and for sure they will do that before replacing your cats, if your milage is under 80k, federal emssion control law will suit you and stealership will replace your cats free.

lots of cases that cats failed before 80k miles, especially for AVK-3.0.

price to test the O2 voltage and cats in stealership is around $120.

[FPBBrandon]

Well, when we did the scan on a regular OBDII Reader, P0420 is the only code it threw. The guy at autozone even said he was surprised because "Audis typically dump 6 or 7 every time [he] reads one" - Hater I don't have access to a VAG tool so I can't check that route.

Stealership won't get me in to test until next week. I'm kind of worried about driving it for the week that I have to wait to get it in, because I'm spending the weekend at my folks, 100 miles away from where I live. The thing that makes me nervous is the turbo kicking on at such low RPMs and staying on almost all the time. I don't want to kill my turbo from something like this, I don't have the $$$ for a turbo replacement sitting around.

Is it alright to drive the car back or should I flatbed it?

[diztek]

funny thing. i went to my mechanic to have him listen to a rattle that i was hearing (ended up being the heatshield under the turbo). anyways, while we were driving trying to listen to the rattle, a friggen cel pops up. ends up being that code. i cleared it, if it comes back im def. going to the dealer. im at 69k miles right now so, i have some time.

[Mike02A4]

I got that code once. Took it to the dealer, picked it up the next day with a brand new Cat converter installed 100% free of charge

[monkey323i]

I got that code once. Took it to the dealer, picked it up the next day with a brand new Cat converter installed 100% free of charge

that is pretty lucky for you.



Usually what the dealers do:

1. Clear the code.
2. tell u to wait if the codes do come back after several days.
3. Rescan the code and test the voltage on O2 sensors.
4. final schedule for replacement/repair.

[B6480Avant]

if i come in with this code and it is a bad cat P0420 will they charge anything just to scan for the code ?

i used to have a truck and when i got codes and showed them the receipt from auto zone they would say "we have to pull the codes ourselves" and it cost $120 to do it !!!

[NyteEscape]

i have been getting this for a little while now, just keep clearing it.

currently, i'm at 68k miles. however, i'm also lowered. if i take it to the dealership, is there any chance they could blame being lowered and hitting something to be the cause?

or should i just find other ways to go?

[pogi]

that is pretty lucky for you.



Usually what the dealers do:

1. Clear the code.
2. tell u to wait if the codes do come back after several days.
3. Rescan the code and test the voltage on O2 sensors.
4. final schedule for replacement/repair.

Yep, just threw this code the other day and the Dealership basically said the same EXACT thing. I'm at 79.7k miles

[Turb_Oh_A4]

the dealership has to prove how your lowered car broke the Cat. so if you have a huge dent and your honeycomb is dent then they win, but your cat is very high and hidden so there is no way that your car broke it. plus, if the honey comb was broke then you car wouldnt rev very high at all, it happened to my vette so we just punched it all out and ran it empty needless to say the inspection machine/sniffer caught on very quick so we had to buy a new one anyway lol...

[JMRQuattro]

if it's the 02 sensor it's really easy to replace. Just remove the air box on the passenger side of the car. And then you'll have an open space to get to it. From your view it's just at the bottom left of the engine. And you'll see a pipe coming from the turbo and that would be the cat. And it's the sensor farthest away from the turbo, it'll be on your right side from the front of the car screwed into the cat. You just take a wrench, get in there, and unscrew it. Then you unplug it, it'll be like redish brown on the other side of the engine. And from there it's pretty much just replacing the new one and screwing it back in it's original place.

But if it said catalytic converter it's most likely your cat. Because if your 02 sensor stopped reading or was reading poorly your ecu would recognize it was the 02 sensor and give you a code for your 02 sensor. So what's happening is your cat isn't doing a good enough job at keeping emissions down. So you probably have a bad cat. I'd say it's unlikely your 02 sensor going bad would give you a code for your catalytic converter.

[NyteEscape]

i'll give a couple dealerships a call and see what i can get.

[B8Buckeye]

i believe that P0420 code is for low THC levels. you should do a smoke test. that should fix the problem.

[NyteEscape]

i believe that P0420 code is for low THC levels. you should do a smoke test. that should fix the problem.

haha...should this smoke be drawn into the car's intake?..

[FPBBrandon]

I guess I should prologue this, I just saw today that it got necro-revived.

I took the Autozone receipt in to my stealership, and did wind up with a faulty catalytic converter. Stealership ate the parts and labor, and I didn't have to pay for a diagnostic on my car because of the fact I brought the Autozone code in.

So yes, the catalytic converter blew in under 70k on my car :) Epic win, but its fixed now, and I got to drive a B7 loaner around for 2 weeks too! All in all not bad, but if I would've had to paid for it, I think I'd have gone catless lol

[B8Buckeye]

haha...should this smoke be drawn into the car's intake?..

i prefer to use a 2.25" diameter water-cooled pipe for this job, though other pipes will work just fine. first test the pipe for air leaks - ignite the testing material, apply suction, pull the male fitting from the pipe & draw in the smoke. if it draws with no problem, then blow the smoke into the intake. i usually repeat this process several times to make sure i got a good smoke test. I find that it's better to use high quality testing material.

all that hard work typically makes me really hungry, though. time to order a pizza!

[401jeeper]

I have a new cat for my '02 A4 Quattro 1.8T. Once the old one's unbolted from the turbo and the downpipe, will I have trouble getting it out and the new one in? Is there a torque spec for cat to turbo?

[jberger12]

I recently got this code on my stock 2003 a4 1.8T. The cat is only about 30k miles old, but at about 15k into the cat's life it underwent two coils going bad due to the gasket going out. I was on a road trip and probably drove a bit with it like this without noticing till I cut the cruise and got off the road. The problem now is the turbo seems to rev at lower RPM and then boost fast and then suddenly drop off. And then spool again then cut off. This makes acceleration very up and down, especially on hills. Checked the vacuum lines and there are no apparent leaks. Replaced the boost reg valve today with no difference in the turbo problem. Any suggestions?

[Atenza]

Hey all

On the drive home from work today, my B6 threw a CEL. I have an 04 1.8TQM USP. Symptoms were very subtle. Mileage dipped a very small amount, and the turbo seems much more eager to spool at lowish RPMs (2000 instead of what typically seems like 2800-3000).

Took it to Autozone and had the code read, and this is the only one it spat out.

Did some searching, and found that this problem is generally one of two things- Bad Catalytic Converter, or Bad 02 Sensor. My reading also suggested that the Cat is warrantied for 8yr/80k by federal emissions warranties.

I suppose my few questions are:

1. Anyone know the likelihood of 02 sensor vs. bad cat?
2. If its an 02 sensor, how much should I expect to get pwned out of at the stealership?
4. What happened to 3?
5. Does anyone know if theres a DIY on the 02 sensor, and if so, am I putting the car at any significant risk while driving with a faulty 02 sensor while I wait for a new one to arrive?

Noob questions, I've got my flame suit on for sure, but at least I searched

What a way to ruin a weekend :(

You should check these items for leakage...
There is a hose which is not on the picture, but You can find it as "Crankcase Breather Hose"