Volkswagen: Brake booster code tied to cat conv.

[CBR.worm]

Originally Posted By: HawkeyeScott
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.

This is almost the same part list that we had to do with the addition of a number of check valves and hoses on our '04 A4 for a similar problem. In our case the PCV and check valves failed (and melted) sending turbo pressure into the crankcase blowing out the seals (and dipstick) which then became vacuum leaks when the car was not under boost. Also major oil leak. We were getting all kinds of codes. The dealer implied that by 40k they pretty much all do that. In our case after replacing the entire PCV system the error codes went away. After replacing the valve cover and tensioner gaskets the oil leaks stopped.

 

[Vikas]

Was that covered by warranty? Don't these manufacturer put their cars through accelerated wear test schedule? There really is no excuse to have these kind of problems at 40K miles unless the car was severely neglected.

- Vikas "No used Audi for me"

 

[mechtech2]

This is not actually a recall, but should be free service if you complain about it.
A hissing leak at idle s the normal complaint.

 

[Vizzy]

Mechtech2....

if the brake booster is allowing unmetered air into the air flow that affects the O2 sensors wouldn't that consititue it as being part of the emissions system? I'd call VWoA on this and relate the scenario...

I know that the Federal Emissions Warranty this is required by law seems to include ANY item that has a relation to emissions controls and that air leak CLEARLY affects the O2 sensor according to you.

 

[Arthur_G]

Hello, I know this is a old question but I am dealing with a similar issue. In my case the bad cat caused the booster not to work properly. The vehicle has no vacuum leaks. But it has so much back pressure. It's a 2007 Hyundai sonata. V6 two manifold cats. I removed the upstream o2 sensor to relief the pressure and then the vehicle runs better and booster is restored.
So I think Volkswagen should have looked at the cat. In your issue. Damb cars!!!!