Volkswagen: Brake booster code tied to cat conv.

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HawkeyeScott

HawkeyeScott

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Posting again for a co-worker now that a second Volkswagen dealer has told him they won't fix a catalytic converter code under warranty until he fixes his brake booster code first. This is for his wife's 2003 Passat.

Dealer says 90% of the time the cat code goes away when the brake booster issue is fixed. We talked to an independent shop that works on VWs and they've never heard of such a thing.

I'm skeptical - never before have I heard of a brake booster issue somehow being tied to a cat. converter. So if they really are being honest at the dealerships, I assume it's some weird code oddity and not an actual problem with the brake booster that's causing a cat. conv. issue.

Anyone heard of anything like this?

The 8-year cat. warranty is up in 8 weeks.
 
I've never heard of a brake booster code, or even method of automatically diagnosing it.

My sister had a cracked exhaust manifold in her hyundai accent that was causing a vacuum leak, and o2/cat related codes. There may in fact be a vacuum leak in the booster and something has been lost in translation between tech-servicewriter-friend-you-us.
 
UTTER NONSENSE!!!!!

There is NO connection between the two, unless perhaps there is an ECU or electrical glitch, but I really doubt it.

I have owned VW products for over 25 years now and the dealer network is really spotty....

Tell your friend to go to another dealer!

I would RUN not walk away from that dealer..it appears to me that they are trying to make more money by BSing him.
Not a bad idea for him to call VWoA and let them know about ths situation . They need to know what [censored] their dealers are pulling!

After the final warranty job I suggest that ANY VW owner seek out a reputable independent VW shop..they almost always seem more competent than the dealers and the price is much less expensive.
 
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He just showed me the Autozone code readout he had done over the weekend. It's P0420.

http://repairpal.com/OBD-II-Code-P0420

He is also back from the dealership with a part list of what they say would fix the brake booster issue: Valve cover gasket, jet pump, tensioner gasket and PCV valve.

He just told me his next call will be to the independent shop who recently did his brakes. I'm hoping he gets this figured out quickly.
 
The P 0420 is the catalyst system below threshold, my guess is that the catalytic converter and or related emissions items are failing or have failed.

Those are emissions items that would have NO relation to the brake booster item.

ALSO ANY related part to the catalyst system replacement WOULD BE COVERED UNDER THE EMISSIONS WARRANTY...so if the car has less than 80k miles on it or 8 years THEY HAVE TO REPLACE IT FREE OF CHARGE!(100k or 10 years in CA I believe)

Like I said take it to another dealer...

They don't like the fact that they are only getting paid warranty rate for the cat converter...so they are trying to get your friend to spend for the brake booster.

Even if by some crazy chance there is a relationship that vacuum leak in the booster affects the emissions system they would have to replace that free too. The Federal Emissions warranty provisions require it! But this isn't true.

Go to another dealer!
 
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It is possible that the brake booster has a internal (vacuum) leak and is causing a lean condition. And therefore the ECM is setting a code because it believes the catalytic converter is inefficient. We had a BMW in the shop and it was causing the same problem. And if that is the problem the brake booster is not covered under the emissions warranty only the catalytic converter.
 
I dont know what a "brake booster code" would be, but a significant vacuum leak at the booster would kill any chance of the engine running properly. The ECU most likely cannot compensate for a large vacuum leak and a myriad of prblems ensue. Absolutely agree, gotta fix the booster first(if it has a leak) B4 proceding with any engine codes. Assuming it s a torn diaphram, Maybe get a booster at the salvage yard. Maybe its just a craked elbow fitting or backfire preventer 1 way.
 
Here is the crazy part of this story. The P0420 code will neither kill the car nor the owner. On the other hand, brake booster code (whatever that may be) has the ability to turn in to a very bad day!

You need to put your co-worker straight.

- Vikas
 
If there is a brake booster code, as several people have already mentioned, there could very well be a non-obvious connection between the two. If the brake booster is allowing air into the intake past all the measurement devices like IAT and MAF/MAP, the engine could be running lean, which could cause lean or rich running conditions. Either of those could overheat and damage a catalytic converter.

That said, I would have expected other codes like fuel trim level codes or other O2 sensor codes if the problem was severe. But regardless of the seemingly unconnected systems, there definitely could be a connection if the brake booster has a leak.
 
It should be interesting to see the results. One group of posters consider a connection between the two nonsense, and the other group sees the possible connection between the two.
 
While I agree the connection between the two may not be direct, why doesn't he just get the brake booster fixed and see what happens? Doesn't that seem like the right thing to do?

robert
 
The brake booster issue is known. It is a leak. You can hear a hissing at times in the passenger compartment.
There is no code for this, so people on this forum are misled a bit.

Any rich /lean can affect a O2 or cat code.

Done.
 
Going by the code apparently this uses a mechanical vacuum pump,i wonder if the booster is even connected to direct engine vacuum?
If not there should be no reason for a leak causing mixture issues.
If it is then it could theoretically cause a P420 but it would have to be leak larger than the ECM could compensate for.
 
Originally Posted By: J. A. Rizzo
If there is a brake booster code, as several people have already mentioned, there could very well be a non-obvious connection between the two.
I dont know if its just me - but it not a "non-obvious" connection at all. Significant Unmetered vacuum leak into the manifold cannot be compensated for by the ECU with trim. Of course that assumes the "brake booster code" = vacuum leak - as it did 'back in the day'... .
 
My point was that if you have problem with the brake, you get it fixed as soon as possible and then worry about cat converter.
 
Sounds like trying another dealer would be a good idea.

Brake boosters are usually fairly easy to test, and a major vacuum leak would probably show other obvious problems. You shouldn't need any tools for a basic test, just use the brake pedal.
 
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