Need help finding Front (Upstream) O2 (A/F) Sensor
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This is a discussion on Need help finding Front (Upstream) O2 (A/F) Sensor within the Everyday Impreza Talk forums, part of the Community - Meet other Enthusiasts category; 2011 WRX Prem. This sensor was fine, but since placing it back into the collector after replacing my stock up-pipe, ...

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    For External Use Only irickchad's Avatar
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    Need help finding Front (Upstream) O2 (A/F) Sensor

    2011 WRX Prem. This sensor was fine, but since placing it back into the collector after replacing my stock up-pipe, my car throws code P1153 after a half hour or so of driving. It's listed as an O2 sensor by some sites, and air/fuel on others, but I know it's the one the accessport reads air/fuel with. It seems to run, idle, etc, just fine, but then will suddenly peg to 20.8 AFR and throw a code, especially while cruising on the interstate. I found it for $109 on Amazon, and $103 on RockAuto, just wanted to see if anyone can find any better deals, or if anyone has had any experience with this issue and has fixed it without sensor replacement.

    Here's a link to the one I found on amazon, it's Denso PN 234-9108 I think it's the right one, definitely trying to double check before I order a new one. Amazon.com: Denso 234-9108 Air Fuel Sensor: Automotive
    I have an STi with an intake and no tune, I never change my oil, and my wheel spacerz are mad tyte.

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    voidin warranty since 05 unseen's Avatar
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    is this bank 1 sensor 1? how many wires and pins?

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    For External Use Only irickchad's Avatar
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    Bank 1 Sensor 1. I haven't removed the harness and the whole thing is heat wrapped, so I'm not sure. It's whatever's stock for the '11.

    I keep getting annoyed because I find PN's that say they're for upstream and they're for downstream, etc. Shouldn't be this hard just to find the correct sensor, lol.
    I have an STi with an intake and no tune, I never change my oil, and my wheel spacerz are mad tyte.

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    Village Idiot McBill's Avatar
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    There is no O2 in the up pipe. The sensor in the up pipe is a EGT sensor. Did this one go back in when replacing the up pipe?

    Sent from a long time ago, in a galaxy far, far away
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    Quote Originally Posted by McBill View Post
    There is no O2 in the up pipe. The sensor in the up pipe is a EGT sensor. Did this one go back in when replacing the up pipe?

    Sent from a long time ago, in a galaxy far, far away
    yeah isnt there an 02 in the header, down pipe and after cat?

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    Village Idiot McBill's Avatar
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    There is only two. One at the very end of the header, and one after the cat in the downpipe.

    Typically, when someone installs an aftermarket DP they will have a bung welded in before the cat in the downpipe for a wideband O2 gauge. That's the only time there should be three. And the wideband will have no influence on the operation of the car. It's strictly for gauge use and sometimes data logging.

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    Quote Originally Posted by irickchad View Post
    Bank 1 Sensor 1. I haven't removed the harness and the whole thing is heat wrapped, so I'm not sure. It's whatever's stock for the '11.

    I keep getting annoyed because I find PN's that say they're for upstream and they're for downstream, etc. Shouldn't be this hard just to find the correct sensor, lol.
    yeah ive run into that part number problem as well. are you opposed to finding them on ebay? theres genuine denso bank 1 upstream sensors on there for under 100. i bought a rear o2 for 25 bucks, and its working thus far.

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    For External Use Only irickchad's Avatar
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    Quote Originally Posted by McBill View Post
    There is no O2 in the up pipe. The sensor in the up pipe is a EGT sensor. Did this one go back in when replacing the up pipe?

    Sent from a long time ago, in a galaxy far, far away
    Yeah, like I said in the first post, this is the one in the collector.. at the end of the header, not I the up pipe, but it has to be removed to access the up pipe bolts.
    I have an STi with an intake and no tune, I never change my oil, and my wheel spacerz are mad tyte.

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    For External Use Only irickchad's Avatar
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    I called Denso to figure this one out. It is indeed replacement part # 234 9108 thru denso if anyone reads this in the future. Hopefully it gets rid of my code.
    I have an STi with an intake and no tune, I never change my oil, and my wheel spacerz are mad tyte.

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    Village Idiot McBill's Avatar
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    That still intrigues me that it went bad like that after an up pipe install.

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    For External Use Only irickchad's Avatar
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    Quote Originally Posted by McBill View Post
    That still intrigues me that it went bad like that after an up pipe install.

    Sent from a long time ago, in a galaxy far, far away
    Idk if I dinged it against the threads too hard while I was installing it, or if the wiring was just brittle after all that time so close to the heat that an uninstall/reinstall messed it up, but it's definitely on the fritz.
    I have an STi with an intake and no tune, I never change my oil, and my wheel spacerz are mad tyte.

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    Registered User nsibanez's Avatar
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    That sucks man.

    I bought mine on parts-geek....forgot the price but it was on the cheaper side close to what rock auto is
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    Quote Originally Posted by nsibanez View Post
    That sucks man.

    I bought mine on parts-geek....forgot the price but it was on the cheaper side close to what rock auto is
    Yeah, now im just hoping it fixes it. Seems to be super common replacement part for the forester guys, from what ive researched... just not so much for us.
    I have an STi with an intake and no tune, I never change my oil, and my wheel spacerz are mad tyte.

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    Registered User nsibanez's Avatar
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    I've come across a few people having to replace it right around 100k. I did mine at about 110 but it set off around 108 109

    A few people were earlier. I've actually seen a brand new 2015 volvo xc60 need one replaced...some crazy things happen

    I can see that if the wire was frayed a bit, that can cause intermittent power or signal
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    For External Use Only irickchad's Avatar
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    Quote Originally Posted by nsibanez View Post
    I've come across a few people having to replace it right around 100k. I did mine at about 110 but it set off around 108 109

    A few people were earlier. I've actually seen a brand new 2015 volvo xc60 need one replaced...some crazy things happen

    I can see that if the wire was frayed a bit, that can cause intermittent power or signal
    Like I said, it's really weird. It has varying voltage (via accessport) and at times, measures just fine, then out of nowhere it's at 20.8~ again, and stays there til it decides to start metering correctly again.
    I have an STi with an intake and no tune, I never change my oil, and my wheel spacerz are mad tyte.

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