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Old 04-06-07, 02:43 PM   #1
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Default Answer to "Where is my pre-turbo O2 sensor?"

Since I see this pop up every few months on here I figured I would take a photo of the pre-turbo O2 sensor when I was under my car this afternoon.

Sorry it's not the greatest photo/angle but it was the best I could do and it does show where it is.



Why am I posting this? Because a large number of STi owners seem to think the pre-turbo O2 sensor is in the uppipe. It is not. The pre-turbo O2 sensor is in the exhaust manifold at the collector just before it meets up with the uppipe.

Stock there is a headshield covering up this area, due to snapped bolts and rattles I have removed most of my heatshields, thus it was easy to take this photo.

If you buy an aftermarket header with a large bung at the collector it is for the stock pre-turbo O2 sensor, it's not meant to be used for an EGT probe.

If you see a bung in an aftermarket uppipe it is not meant for the pre-turbo O2 sensor, it is meant for an EGT probe which is standard on WRXs but not there on STis since we do not have a cat in our uppipe.

Hopefully this will sort out any confusion and hopefully the mods will add this into the threads of interest sticky so it will be easy to find.

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Old 04-06-07, 03:48 PM   #2
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Awesome Kevin, thanks for taking the picture...I remember we had a long thread on this a while ago, this will be a good place to refer folks to in the future

Moseying on over to threads of interest now...
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Old 04-06-07, 08:35 PM   #3
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No problem. I'm just tired of seeing this pop up every other month so hopefully this can put some of the mis-information to bed.
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Old 04-07-07, 07:17 AM   #4
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Nice. Adding to the thread, the part number on this sensor is:

22641AA211

With aftermarket headers, these sensors become problematic sometimes. They're expensive, though...
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Old 05-30-09, 11:00 PM   #5
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Default Re: Answer to "Where is my pre-turbo O2 sensor?"

is this the sensor that needs to be replaced if you have a P0134 (2004 sti)?
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Old 05-31-09, 06:37 AM   #6
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Default Re: Answer to "Where is my pre-turbo O2 sensor?"

Also known as the front o2 sensor.

Quote:
Originally Posted by complexx
is this the sensor that needs to be replaced if you have a P0134 (2004 sti)?
I didn't see a p0134 on this page, but p0133 and p0135 are related to the front o2 sensor, so in theory the answer to your question would be yes.
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