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AudiDoc
AudiDoc, Independent Audi Shop Owner
Category: Audi
Satisfied Customers: 6457
Experience:  I've been working on Audis since I was 18 and own an independent Audi repair and performance shop
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Audi A6 Quattro: Unable to pass vehicle inspection on a 2000

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Unable to pass vehicle inspection on a 2000 audi a6 2.8 quattro. It's kicking out code p0431, p0421 & p1423... What needs attention? Thank You.

AudiDoc :

Hello, I'm Jason. I will do my best to answer your question quickly and accurately using the information you have provided.

AudiDoc :

The 421/431 are catalyst efficiency codes

AudiDoc :

The 1423 is related to secondary air low flow condition on the right(passenger) cylinder bank

AudiDoc :

you will need a pair of cats, and then need to do some vacuum testing to the right side combi-valve on the back of the cylinder head

Customer:

cats as in catalytic converters?

AudiDoc :

the secondary air system is in place to heat the converters to operating temperature more quickly during a cold start.

AudiDoc :

yes, correct

AudiDoc :

make absolutely sure to use VERY good quality catalytic converters

AudiDoc :

otherwise the codes will come right back

Customer:

Ok... Is the combi-valve easily recognizable?

AudiDoc :

let me show you a picture

AudiDoc :

they're about the size of a small yogurt container

Full Size Image

Customer:

ok. fantastic, that helps tremendously.

AudiDoc :

very glad to help

Customer:

I'll get started. thanks again.

AudiDoc :

sure thing. Take care

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