JBC Quattro

Hello all,

I have a 1998 Audi A6 2.8L NON Quattro, AHA engine, 4 door...125,000 miles

My check engine light came on Sunday...took to mechanic Tuesday (today). He said both my catalytic converters (cats) are bad. The diagnostic computer he hooked up did NOT indicate the O2 sensors were bad. I don't know the code, but he said something about the Back 2 were bad. Was this indicating the O2 sensors, or the back 2 cats. I don't think I have pre-cats (he didn't see any, but he's not an all Audi mechanic), but the Quattro may which could have confused the coding??

Is this possible? Should I get all 4 O2 sensors replaced as well? They have yet to be replaced (per previous owners records) to date, and my mechanic said sometimes they rust and aren't able to be put back on even if they are good (True?).

My mechanic said it is possible for the O2 sensors to go out, and then the cats, within a couple days, but it is very rare.

Is there an underlying cause I need to find if the cats went out but the O2 sensors didn't? I just don't want to have them replaced...then a couple months later have to replace them again if something other than the O2 sensors caused the issue.

Does anyone know if there are pre-cats on my car?

Universal cats or the super expensive ones? The universal are sooooo much cheaper. Are they too good to be true? My mechanic quoted me $180 for each cat, and I found the O2 sensors for an average of $130 each.

Thank you for any and all help!

divekyra

I recently had the catalytic converter changed on my A6. The first mechanic I went to told me I had bad O2 Sensors and wanted to change all of them, he NEVER mentioned the Cat. I went to an Audi place and got a second opinion, they replaced the Cat (free of charge because it was a little early- under the 100,000mile mark) and the O2 sensors are fine, they are just doing their job.
I am not knowledgable enough, but from this experience it seems that those who want more $ may want to change the sensors before the Cat. Myabe just change the cat and if the O2 sensors are bad, then change them. I do know my mechanic said he's change all of them if they were bad.
What do I know?
Either way, maybe get a second opinion.
The first certified mechanic I went to wanted $4,000 (I kid you not) for repairs of ALL sorts (except the catalytic converter, they said that one was fine!)! I took it to a second opinion and it just needed 1200 (plus free cat).
Given the times and the desperation of some people to make money at any cost, I'd get a second opinion if I am not sure.

K04-S4

A qualified mechanic with VAG-COM will be able to confirm if cats and / or which specific O2 sensor(s) are bad.

Ecmbuster

Cats need to be as good or better than OEM. The engine management system will never tolerate anything less. O2 sensors need to fit the correct heater circuit range. Just because they came from "Bosch" doesn't mean they are "Bosch".

Hire this guy, I trained him
Dan Braucher
330-494-0887
Braucher Service Inc
7780 Wales Ave NW
North Canton OH 44720

hits_15

If you need a new aftermarker Cat.

let me know.

5000Audi

turbo back straight pipe FTW, no need for cats lol..( unless you live in BC haha car care sucks)

but on topic i would take to a person of whom knows VAG-COM and get it rightfully diagnosed

hasbin

I have a cat that needs replacing but the dealership says Audi will not replace because it has not tripped the "check engine" light. I have only 89,000 kms on an 01 4.2, but both cats rattle ...the psgr side all the time and loud. any ideas on how I can "convince" Audi they need to replace under warranty? The dealer (St. James in Winnipeg) wants $1600 per side! Help!

Ecmbuster

Warranty on an 01?
It's obvious that the dealer has no real intelligence. Converters are a related emissions part and in their "small minded view", have the owner wait a little longer and later have the customer "pay" for parts that should be replaced. If it fits a warranty period, testing the CAT efficiency would be a good step. Demand that a continuous work order is kept up and complain HARD!
As for no MIL, I find that very odd.

Fire the dealer, find another and call Audi Canada for slightly better service.
Ask them is they have an anti-rattle update for those converters.

You should also test the fuel quality.

hasbin

Thanks ecmbuster....not sure what you mean by "no MIL"? The dealership said Audi's response was "it was not an emissions issue, but a drivability issue, for which I have no warranty"... the emissions warranty that the cats are under is a 8 year 130,000km one, and my car's "in service" date is early October 2001...and I have only 89,000" kms on it, so it would be covered under the emissions warranty....apparently incessant rattling (and making the car sound like a junk heap) is not enough...Check engine light would show some sort of code for the cats and then they would replace> Unfortunately, I cannot fire the dealer as they are the only one in the province! Gas is always #1 from Petro Canada (gas card)

Ecmbuster

MIL
Malfunction Indicator Light.

Record the noise and submit that recording to Audi Canada. I'd still ask if there's an anti-rattle campaign. (That was sarcasm)

Beg, borrow or steal two used rear O2 sensors, Plug them into the harness only, do not thread them on to the rear CATs. Drive the car and MIL will set.

Plug the original harness back in and give it back to the dealer. Repeat the process continuously. They'll never figure it out.

Have an independent service facility test the CATs via 5 gas analyzer and test for current and for fault history.

As for the person that qualifies the issue as drivability, ask for their qualifications and if those noises can be qualified as "normal Audi noise" (Sarcasm again)