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Old 09-25-2014, 01:46 PM   #1
Scooby Newbie
Member#: 327489
Join Date: Jul 2012
Default 2008 Impreza 2.5i, CEL P0134

Having a P0134 (Front o2 sensor) and occasionally a P0031 (misfired?) Which from what I've read are related and both point to a bad front o2 sensor.

I'd like to do the work myself, since it seems pretty simple.

Not 100% sure which sensor is the o2 sensor. I have one before the cat, that has a grey cable/plug and one that goes into the cat(i think) that's orange. I can post pictures later if needed. I think the grey one is the one I need to replace. Anyway, I found 2 Denso (I think these are OEM?) sensors, not sure which one I need.

If I take the old one out will it have the part number written on it somewhere?

Here's a link of the 2 sensors.

Denso 234-4445
Denso 234-9123
Any help would be great, thanks.
Levi3434 is offline   Reply With Quote
Old 08-28-2019, 07:16 PM   #2
Scooby Newbie
Member#: 297080
Join Date: Oct 2011
Location: Pittsburgh, PA
2008 WRX


hate to revive an old thread but its the only one i found that'close to what i have to ask/post.

i have 2008 WRX. ive owned it for all of three deys. im new to subbys.

i have a CEL, TPMS and Stability control light on and a blinking cruise control light. the only codes that come up are
-P0031- HO2S heater control circuit low (bank 1 sensor 1)
-P0134 - O2 sensor circuit no activity detected (bank 1 sensor 1)

car also turns off once in a while when im either slowing down in neutral or stopped completely in neutral. steering also gets hard during some turns but im guessing thats the car trying to turn off and power steering not working.

any insight or help is much appreciated
Goliat6288 is offline   Reply With Quote
Old 09-02-2019, 10:28 AM   #3
Scooby Newbie
Member#: 445600
Join Date: Apr 2016
Chapter/Region: Tri-State
Location: Rafferty Subaru, PA
2002 Outback Sport


You most likely need a new A/F sensor. The A/F (air/ fuel) sensor is what Subaru's use for an upstream O2 sensor.
CaptainSlowbaru is offline   Reply With Quote
Old 09-11-2019, 06:53 PM   #4
Scooby Newbie
Member#: 297080
Join Date: Oct 2011
Location: Pittsburgh, PA
2008 WRX


Thanks captain

i tried replacing it and ended up rounding it out. took it to shop and they got it out and replaced. cel, cruise control and stability control light off now. TPMS light still on and blinking so im guessing the sensors are out of battery. no biggie though

edit; oh and my car isnt turning off anymore when slowing down or coming to a stop

Last edited by Goliat6288; 09-11-2019 at 06:54 PM. Reason: more info
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