Upstream 02 replacement!!!

Is there an easy way to get to the upstream 02 sensor? I am going to replace the one on my 08 Legacy and 06 Outback. It looks like a pain to get to. I attempted tonight but stopped due to the fact I need the car for work and did not want to break or bend something. this cant be that hard. Hell I pulled the motor on this thing. Just chime in.

On the turbo cars you can get it from the wheel well.

 

Is there a reason for replacing it?

(this is the NA forum...)

Ahaah thanks dookie. Yes my car is 08 2.5i. There is no reason for replacement. I have a nice car fund that I just save money in and want to spend some cash on the car. The car has 142K mile's on it. I have pulled the motor and replaced the HG's, water pump, and everything you could think of with OEM Subaru parts. I replaced the sensor before the cat two months ago cause the car was throwing codes all the time. After the new sensor, it runs very well. I am wanting to replace the upstream because I found some very nice clearance 02's (that I researched before I bought to make sure it was not junk) from rockauto for 46 buck.These were originally 93 buck. Hell if they go bad oh well I will buy two more. They look like the 100 dollar quality one and the company has a good rep.

I am well aware this is the NA forum. If you look for where it is located, that would tell you how to get at it... I looked at the diagrams and it should be accessible from the wheel well.

 

O2 sensors are typically around $40 for a universal fitment Bosch or Denso that is the same sensor.

 

It seems like you just want to spend money on a replacement that may or may not be needed for peace of mind.

if the sensor is not bad, there is no need to waste money on a replacement.

I understand the do not replace this and that. To me its not a waste of money. I have the parts. Everyone treats there cars different. I want to replace it since I replaced the other one. That's just me.

 

I know were it's located and the one you talking about by the wheels well is the LGT or WRX. The rear on the cat was easy to replace. I had an 04 STI and know a good deal about the location. On the 2.5I it's pretty much right in front of the oil filter cause I can see the filter.

 

I will post a picture of the location. I was thinking I need the tall 02 socket. I have the harbor freight one that did the job. I am just looking to get leverage in the location.

I thought of this thread when I was replacing my plugs tonight, and took a few pictures from above with the ram air piece removed, and whole air box removed.

 

If it were me, I'd probably try to remove it from above with the ram air out of the way. I've never replaced either of my oxygen sensors, but that looks like the way I'd try.

 

Here's a picture I took a few years ago from below, can't really see it there.

http://legacygt.com/forums/attachment.php?attachmentid=195015&d=1414179093

 

And I can't remember how much of the sensor you can see from the oil filter area, shown below from another older picture. But it looks like it might be annoying to access with the oil filter there.

http://legacygt.com/forums/attachment.php?attachmentid=186822&d=1404487490

 

*Come to think of it, I think you'll have to remove the ram air anyways to unplug the sensor. So another reason to try from up top first.

I thought of this thread when I was replacing my plugs tonight, and took a few pictures from above with the ram air piece removed, and whole air box removed.

 

If it were me, I'd probably try to remove it from above with the ram air out of the way. I've never replaced either of my oxygen sensors, but that looks like the way I'd try.

 

Here's a picture I took a few years ago from below, can't really see it there.

http://legacygt.com/forums/attachment.php?attachmentid=195015&d=1414179093

 

And I can't remember how much of the sensor you can see from the oil filter area, shown below from another older picture. But it looks like it might be annoying to access with the oil filter there.

http://legacygt.com/forums/attachment.php?attachmentid=186822&d=1404487490

 

*Come to think of it, I think you'll have to remove the ram air anyways to unplug the sensor. So another reason to try from up top first.

 

Yes, that is the exact sensor I am talking about. The one in front of the oil filter. Yes you do have to remove the ram air. It is annoying. I am going to try from the top again and use a long 02 Sensor. I will make a how to for the 2.5i people. I have a shelf full of new stuff I am adding. Guess I am bored.

Well, after replacing both O2 sensors I'm still throwing P0139 code.... send your bin of extra parts my way. MAYBE one of them will shut my OBD2 up! I MISS cruise control with the damn blinky light and Check Engine.

Well, after replacing both O2 sensors I'm still throwing P0139 code.... send your bin of extra parts my way. MAYBE one of them will shut my OBD2 up! I MISS cruise control with the damn blinky light and Check Engine.

 

• The oxygen sensor is faulty
  
• The wiring to the sensor is broken / frayed
  
• There is an exhaust leak
  

 

Read more at: http://www.obd-codes.com/p0139

Copyright OBD-Codes.com

 

Have you tried investigating the other two possibilities?

^ I agree. While an exhaust leak may not make a lot of sense at first, I'm reading the amount of back pressure in the exhaust (too little?) could throw that code. Having an exhaust leak could alter the back pressure and f things up.

scott, I can send you my old one lol.

Have you managed to write a how-to?

Have you checked the harness? Trace that to its terminus and ensure there are no issues, sometimes things get caught/cut/nicked while working in and around the engine bay.

 

Also is the sensor in tight? Both of them? All piping connected snugly? I would stick to DENSO sensors they seem to never cause issues. Ive used them as replacements on both my LGT and 2.5i.

I am going to do it tomorrow, Including another hub on my Outback, and full JL Audio install. I will have a write up.