# O2 sensors MIL



## Massboykie (Aug 15, 2006)

Hey Guys
I recently started getting an engine light. VAG-COMed it and it turns out both (left and right ) rear O2 sensors are not reading correctly. What are the odds of both of these going at exactly the same time? The car only has 53K miles on it, so it seams early, but I may be wrong.
I found the universal Bosch replacements for around $60 each so replacing them is not that bad. I was just wondering if some kind of a vacuum or boost leak could be causing this? 
Any advice would be appreciated.








Cheers
Massboykie


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## GLS-S4 (Jun 6, 2005)

*Re: O2 sensors MIL (Massboykie)*

Any other codes or just the two rear O2s?
What are the actual codes?


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## Massboykie (Aug 15, 2006)

*Re: O2 sensors MIL (GLS-S4)*

Hey GLS
Here we go...
2 Faults Found:
17584 - Bank1: O2 (Lambda) Correction Behind Catalyst: Control Limit Reached 
P1176 - 35-00 - -
17585 - Bank2: O2 (Lambda) Correction Behind Catalyst: Control Limit Reached 
P1177 - 35-00 - -
Cheers
Massboykie


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## Massboykie (Aug 15, 2006)

*Re: O2 sensors MIL (Massboykie)*

I read somewhere that this could be boost or vacuum.. I'll do a presure test this weekend and report back.
Cheers
Massboykie


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## Massboykie (Aug 15, 2006)

*Re: O2 sensors MIL (Massboykie)*

No vacuum problems I could find. Presure tested fine. I cleaned the MAF as someone suggested that could cause weird issues. 
Got in under the car, but getting those puppies out seem to be way more of a bitch than I thought. The wires run all the way forward to the firewall and are tie-wrapped to the tranny etc. Not having the car on a lift makes this a major pain in the @ss.
I haven't VAGed the car yet to reset and see if the MAF cleaning worked. 
Will post an update.
Cheers
Massboykie


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## hrkljus7 (May 9, 2006)

*Re: O2 sensors MIL (Massboykie)*

How did you make out?
I have similar problem on my '01 2.7T, codes p1176 -O2S Correction Behind Catalyst, and p0431- Warm Up Catalyst Efficiency Below Threshold (Bank 2). I hope it's second 02 and not the convertor. 
Where did you find o2's for 60 bucks? Also, is there a link for cleaning MAF, I coudnt find it.


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## Massboykie (Aug 15, 2006)

*Re: O2 sensors MIL (hrkljus7)*


_Quote, originally posted by *hrkljus7* »_How did you make out?

Hey Hrkljus7
While I had everything apart while checking for boost leaks, I cleaned my MAF sensor and was planning to replace the sensors the next weekend. As it turns out the codes did not come back after the MAF cleaning. Well worth trying. I used CRC spray, but you can use alcohol also. What is your miliage? I'm at around 55K miles.
I bought the sensors from http;//www.RockAuto.com
Cheers
Massboykie


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## Massboykie (Aug 15, 2006)

*Re: O2 sensors MIL (hrkljus7)*


_Quote, originally posted by *hrkljus7* »_How did you make out?

Update...
My joy was short lived...








MIL is back after I filled up the car again... The odd thing is that the O2 sensors were reading perfectly after I cleared the codes recently. None of the readings were out of spec (Min Max). I am planning to put some fuel system cleaner through it to see if this helps... Just as an FYI.. I put in Sonoco gas both times I started having inssues (from the same place). Inbetween I was using Shell without problems... I wonder if there is something there...
Cheers
Massboykie


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## 2035cc16v (May 18, 2000)

*Re: O2 sensors MIL (Massboykie)*

its the gas...








weve been seeing a LOT of o2 failures lately, audi is saying its the gas and is only recommending Shell for the time being...at least here in New England


_Modified by 2035cc16v at 5:00 AM 6-6-2008_


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## Massboykie (Aug 15, 2006)

*Re: O2 sensors MIL (2035cc16v)*


_Quote, originally posted by *2035cc16v* »_its the gas...








weve been seeing a LOT of o2 failures lately, audi is saying its the gas and is only recommending Shell for the time being...at least here in New England..

Seriously! That really pisses me off! We are paying more than ever for gas, and they end up selling us crappy stuff! Damn!








...off the soapbox I go...








I filled it with Shell yesterday and also put some fuels system cleaner through it for good measure. Pulled the codes this morning, and it was the O2s again and also some misfires. I'll see if these go away.
Cheers
Massboykie


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