Catalytic Convetters, dealer brand (VW), or "off brand" What's best?

I have an 02 VW Passat 4Motion Wagon with 170+ miles on it. The CEL is on all the time now, and the dealer says I need new Cats for which VW wants $2500.00 for the pair.

I want to fix it, but wonder if “off brand” (not VW) catalytic converters are available for much less money, and where to get then installed.

Will “off brand” (non VW) Cats be compatible with the VW exhaust system needs? Will the VW oxygen sensors that the dealer says are lighting up the CEL be compatible? That is, will the CEL go off once the “off brand” converters are installed? Should I get new oxygen sensors when i get new Cats?

I learned on CarTalk that the diagnosis can be confirmed by a burning smell when the car is idling that goes away once the car is moving. I have that smell.

(I thought the smell was an oil leak for a while, and paid dearly for several repairs for that problem until finally the dealer says it is the Cats.}

What produces that smell? Why doesn’t the smell go out the back exhaust when the car is idling instead of seeping up into the passanger compartment? (The smell is strongest on the driver’s side if that means anything? And, lately I detect an unburned gas smell in the exhaust as if the mixture is too rich. Is this related to bad Cats?}

Is the smell toxic? Is the car dangerous to drive?

There are two catylitic converters on this car. Do i have to fix both? Do I have to fix this problem at all or can I ignore it and just continue driving the car?

Anyone out there with experience installing “off brand” catalytic converters on a Passat or any other car? Any one with advice about where to get a good “off brand” catalytic converter installed for a fair price in Boston, the North or Western suburbs or Southern NH?? Also, any one know a good VW mechanic in the Boston area, Western suburbs, North shore, or So. NH who has the correct diagnostic equipment that he can actually interpret correctly from the printout. Sometimes my VW dealer seems not to know what the codes are telling him.

I drive fast, but mostly highway driving , and I have babied this car as far as oil changes and every possible repair over its life. Would love to get 200, or 250K miles out of it.

A catalytic converter is a catalytic converter. And all must meet the EPA requirements as far as performance and construction. So if you can locate aftermarket/universal catalytic converters that fit your vehicle, any muffler shop can cut out the old cats and weld in the new ones.


Since you have a very similar post already going I will address only the question “will new cats. and sensors keep the cel from comming on” it can come on for other reasons and you are smart to question if part replacement will solve the cel problem,the answer is, Its not guaranteed,we have many posts from people that have codes for cats. and 02 sensors that get the parts replaced and still deal with codes for cats. and sensors.

Thanks. sorry about two similar posts. I’m new at this.
Do fault codes have to be reset once a repair is done, to turn of the cel, or do things reset automatically to a “no fault detected” state?
Do you have an idea what else might be wrong if a catalytic converter failure fault code is indicated but the repair doesn’t turn off the cel, that is assuming no other fault codes are indicated in the scan ?
Do you have a preference for VW dealer parts in this case vs. “off brand”?

Thanks, Tester. That’s what I suspected.
The problem with my VW is that the engine pipe, flex pipe and cat are one piece and there isn’t much room between the flex pipe and cat to cut and splice in a new cat. Also, I don’t know where the oxigen sensors are, and am not sure that any muffler shop guy knows or cares where they are (though that may not be a fair observation). Am hoping to find someone who knows this.

When I run into that situation, not only do I weld in a new cat, but also one of these

There’s always a way to get around these type of problems.


It could go like this. You buy cats. and sensors from garage X. They put them in and clear the codes send you on your way. 2wks latter a cat or sensor related code pops up. garage X tries to figure it out they can’t and throw up their hands. You go back to the Dealer they say “you didn’t buy our parts we can’t help you”. Then you start looking for a independent that has better diagnostic skills than garage X.

Failures that can set codes that lead to mistaken replacement of cat. and sensors are ECU (module failures) wiring failures,misdiagnoised engine conditions,probably more.

Check out a thread on this Forum,“Sorid Tale of a Check engine Light”. I think CT stopped it because it became so long.

In short make sure the guy installing the cats. and sensor can also diagnois.

Probably the reason the Dealer insists on doing both cats or none is they don’t want to tell you its one and then its the other. Look that situation of having two cats over closely or is this a V-6 engine (I am fairly new VW illiterate)

If it is a V-6 the code should tell them what bank,what is the code saying “low efficiency” or something similar?

If you have someone weld in a stainless steel piece like Tester described, make sure they know what they’re doing. Stainless steel is tricky stuff to properly weld (even worse, if you’re welding it to non-SS). In fact, these couplings appear to be intended to be clamped, not welded.

We did all of our BMW cats. with clamps (factory specfic) worked out good. System was SS,double wall if I recall correctly.

Are wiring problems are hard to track down? By “ECU” do you mean the cars electronic control unit.

Yes ECU=electronic control unit. Electrical problems can test the best of us,sometimes you win through luck,it is better to have a comprehensive understanding of the system you are working on and a more than basic understanding of electronics combined with a stratagey and common sense.

Did you give the thread I mentioned a look?

Let us know about your decisions and progress,we will walk you through this. I am handicaped in regards to very little new VW experience.

oldschool, et al,
I checked out that thread “oldschool” referred me to, and learned some things, (didn’t read it to the end, should I do that?), that this can be a very hard problem to solve, and since I don’t do my own work it is likely to be expensive, and despite best efforts, repair shops can be wrong about fault codes or not know where to go next if the repair doesn’t reset the code.

I don’t mind driving with the cel on, knowing what it means, I think I know, but as long as it’s on for a known condition it keeps me from knowing about some other problem that might turn up.

Since the thread you referred me to shows that specific fault codes, seeming to point to a particular condition, may in fact indicate some other problem, I think I need to get the specific fault codes from a new scan at my next scheduled service, post them here, and try to find a VW expert (hopefully a private not a dealer) who has the right equipment and know how.
I would like to keep getting CT advice along the way. Thanks for the help so far

If we were in Germany i think this could be fixed without a problem. Have to admit, am tempted to buy a used VW 4Motion wagon with lower milage, and dump this one, but it runs so well and has so, so many new parts.

Thanks for the help so far.

The thread I refered you to is a extreme example.