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A4 V6 DOWNPIPE /CAT QUESTION

Discussion in 'A4/S4 forum(B5 Chassis)' started by HenryL, Feb 7, 2012.

  1. HenryL
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    HenryL New Member

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    [Feb 7, 2012]
    Hi - I posted this below on VW/Au forum but no nibbles yet and time is ticking unfortunately - Can anyone here throw any light on this?
    Does the fact that I get cat efficiency fault code mean it must be a dual sensor setup or can this still be raised if there is only a single lambda sensor ?

    It's a 2000/X-reg A4 B5 30V V6 2.4 SE fwd manual petrol, eng.type AML

    ==>

    Left hand exhaust down/front pipe has split open at hanging bracket point and need to repair it in a bit of hurry. Looking for a replacement downpipe/cat to fit and found a 'non OBD' part online which I presume is no use (?) - but am a bit confused about the exhaust system and sensor layout...

    The broken bit of pipe is roughly under the left hand passenger footwell where a welded-on hanger bracket connects to a sprung hanging point to gearbox.

    Problem 1 - have had trouble getting a manual/info for this car. Got a Haynes for this year for general A4 info but which does not cover V6. In desperation bought a pdf manual from ebayclaiming to cover this model but it didn't and was patchy. Mistake.

    Problem 2 - the car is not outside and I can't go and look at it, but I need to line up parts to repair it as soon as it comes back in few days time.

    First question: It has MIL light and P0420 and P0430 codes indicating catalysts below efficiency. I presume this means it IS/must be an 'OBD type' system - right? Does any sensor at all in the exhaust line imply it is 'OBD' type needed?

    From memory of looking up at it underneath:
    There is a sensor just in front of a/the catalytic converter (I presume) but there didn't seem to be one after/behind the cat converter box, at least not in plain view from where I was looking at the time. I understood the OBD system relied on a sensor before the cat and one after, so I am wondering whether (a) there is a/nother catalytic converter closer to the engine (though it looked like the end of my fractured down pipe was just bolting onto a manifold) (b) there are other sensor/s closer to the engine (c) the box I am looking at, which is roughly under the passenger seat, is not actually a cat at all but a front silencer box (d) something else...

    I was thinking I needed to replace a [downpipe+flexijoint+cat] unit (with a connection point for a sensor in it just before the cat), but now wondering if I've not got confused about what I was looking at.

    Second question: Can anyone confirm how the system is layed out, and what part it is I need to be getting exactly? (Also any recommendation of where to get it would be great as this model doesn't seem to throw up many useful hits.)

    Third question, while I am at it: Any recommendations on source of a manual for this model?

    TIA / Henry
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