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Code #P0421. Please help.

Old 03-13-2010, 12:49 AM
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Join Date: Feb 2010
Location: Pittsburgh, PA
Posts: 125

Originally Posted by [email protected] View Post
Sorry for the late reply guys.

The code IS BACK. I'll try to check the vacuum lines behind each head for the Kombi Valves, and if that doesn't work, I'll check the wastegate.
Jim-- Do you think you can point out to me where this wastegate is located?

Appreciate it!
any luck yet? Is the CEL still coming on? Is it still throwing a p0420?
Old 03-29-2011, 12:08 PM
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Join Date: Mar 2011
Posts: 1
Default Same issue

Has there been any progress regarding this issue. I have the same thing going on with my 02 A4 3.0, and poking around the engine compartment looking for a vacuum leak I found a really loose hoseclamp, I tightened it and I cleared the code with my scanner so we will see if it comes back. i would hate to spend any money if it could be a split or torn vacuum line.
Old 04-07-2011, 10:44 AM
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Join Date: Apr 2011
Location: Chicago
Posts: 1

Is there an aftermarket catalytic converter that is cheaper than the oem Audi ?
Old 01-12-2014, 04:54 PM
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Join Date: Jan 2014
Posts: 4

I know this is an old thread but I am having this same issue with my 02 a4 3.0 quattro (97000 miles). I'm looking for some insight as to how you made out with this code
Old 01-14-2014, 09:10 AM
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Join Date: Jan 2014
Posts: 4

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