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how do you know if you have bad cats or just bad 02 sensors?

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Old 07-28-2006, 05:14 PM
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Default how do you know if you have bad cats or just bad 02 sensors?
I have a CEL with 16805 and 16815.
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Old 07-28-2006, 05:18 PM
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Default What year is your A6?
And, is it a 2.8, 3.0 or 2.7T?
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Old 07-28-2006, 05:18 PM
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'03 3.0Q
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Old 07-28-2006, 06:41 PM
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Default Typically.....
VAG the car and check diagnostic codes, if any. Bad O2 sensors will have fault codes, each for frt (B4 cat) and poor emissions if after cat. Bad cats also rattle and may even completely fail and the honeycomb interior likely will block exhaust in some instances. If you hear an exhaust rattle, its the cats for sure. Either way is $$$.
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Old 07-28-2006, 06:47 PM
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YGM
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Old 07-28-2006, 06:47 PM
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Default how many miles?
if less thena 80K you are covered for the cats byt the EPA warranty.
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Old 07-28-2006, 08:13 PM
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Default I'd like to know the same thing...
I got the 16806 code only "main catalyst bank 1 efficiency below threshold." Originally showed up back in Feb, cleared it and didn't come back for a couple of months. Re-cleared it, and showed back up in a couple of days. Looks like I have some troubleshooting to do. I'm only at 57k on my '00, so if it is the cat, I'm covered. But I'd hate to pay for an 02 sensor at the dealer when I could replace it myself.
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Old 07-29-2006, 09:26 AM
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start wtih O2 sensors. Cheap compared to the cats. it is a DIY, not that bad. Get Zoldmans
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