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Old 10-06-2008, 10:18 AM   #1 (permalink)
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Default How to check o2 sensor?

Hi
I had been getting P0030 codes showing up that seem to clear after about a week or two, then return and clear again for no reason I can tell. That is to say the CEL goes out and no codes show. I was going to replace the sensor, but now I'm not so sure. Wouldn't the sensor either work, or not work? Is there some way to check it before I go through the expense and hassle? I read someplace that an ohmmeter can be used to check for the proper resistance at the ECU wiring. I can't find that post anymore. Anyone able to help? The Forester is an '04.
Thanks!
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Old 10-06-2008, 10:23 AM   #2 (permalink)
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^^

Are you sure the CEL code was P0030? I don't see that one on the list? Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

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Old 10-06-2008, 11:08 AM   #3 (permalink)
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Front O2 sensor heater open. You can check the heater for continuity between pins 3 & 4 on the connector. It should be about 5 ohms.
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Old 10-06-2008, 02:09 PM   #4 (permalink)
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Okay, I found CEL code P0030 here Scoobypedia | Trusted knowledge for everything Subaru | Knowledge / OBDII Trouble Code Definitions but not here Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical ?

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Old 10-06-2008, 03:02 PM   #5 (permalink)
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O2 sensors are good for 100 000 miles. Change it if its giving you problems.
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Old 10-07-2008, 05:01 AM   #6 (permalink)
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OK, thanks for all replies. I have about 98K on my Forester right now, so I guess I'm due. Just wondering if I can check the resistance at the ECU connector so I don't have to jack up the car and remove the heat shield just to access the connector on the sensor. How would I identify the O2 sensor wireing at the ECU?
Also, can anyone recommend a brand and vendor for a replacement? I see several places on the net, including some real cheap universal sensors. I always like to go with advice rather than the prettiest web site.
Thanks!
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Old 10-07-2008, 08:17 AM   #7 (permalink)
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The front O2 sensor (A/F or Air/Fuel sensor) is critical for correct engine operation, unlike the rear O2 sensor that just monitors the CAT. I would get an OEM/factory repacement. IIRC mine was around $160 from the dealership, but should be less via the internet.

My .02 cents worth...:)

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Old 10-07-2008, 08:59 AM   #8 (permalink)
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Thanks. I don't notice any real big performance change, maybe a bit of sluggishness. But I will try and swap it out myself ASAP. I see there is a Walker brand out there for about $129 shipped. I try and avoid the Subaru dealers around here ( NJ ). I can just imagine what this whole job would cost me from them...$100 to read the OBD code, $250 for the O2 sensor, and $200 for labor..then the tax.
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Old 10-07-2008, 10:10 AM   #9 (permalink)
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Quote:
Originally Posted by Hmaxim View Post
Thanks. I don't notice any real big performance change, maybe a bit of sluggishness. But I will try and swap it out myself ASAP. I see there is a Walker brand out there for about $129 shipped. I try and avoid the Subaru dealers around here ( NJ ). I can just imagine what this whole job would cost me from them...$100 to read the OBD code, $250 for the O2 sensor, and $200 for labor..then the tax.
If you're not noticing a major performance or drivability issue, you have time to do some shopping around.

As to having a shop do the work. Now you know why doing the work yourself is better. It's not just the money you save, but the knowledge you gain!:)

You might want to see what Jackie (SubaruPartsGirl), a supporting vendor here on the forum, would charge you for the part. Annapolis Subaru, (866) 509-3019. She's great to work with! I live on the West coast & I buy from her...:)

Keep in mind that you may need a special socket to remove the sensor, especially the front one. They're cheap & you can find one at your local auto parts store.

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Old 10-07-2008, 10:18 AM   #10 (permalink)
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You don't have to get to the sensor itself to test it,there is a long pigtail you can unplug and prob there. No matter though at that mileage you would be better served just swapping it out. It helps if you have the proper tool which you can borrow for free at most automotive places:

Oxygen Sensor removal (02 Sensor) - ScoobyMods
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Old 10-07-2008, 03:24 PM   #11 (permalink)
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Thanks for all the great advice and help! This forum is a goldmine!
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Old 10-07-2008, 03:41 PM   #12 (permalink)
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Here's my version.

O2 Sensor replaced Pics inside!!!
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Old 10-08-2008, 04:25 AM   #13 (permalink)
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This great stuff! I'm beginning to think I can actually do this !
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Old 11-17-2008, 08:03 PM   #14 (permalink)
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Thumbs up Oxgen Sensor removal

Thanks Peaty for the link to remove the O2 sensor. I have successfully replaced the front O2 sensor on my 2005 Subaru Forester. The CEL light has not reappeared after the replace. Thanks a lot for all the pics and the detailed explanation. One thing to note for any other first time O2 replacers, do not attempt to remove the O2 sensor without the O2 socket and a 3/8" drive breaker bar. The autozone guy discouraged me from buying the breaker bar...but when I was lying down under the car and trying to remove the sensor(for almost 30 mins), i realized the breaker bar would have given me more torque than the rachet. I then had to put a hollow rod over the rachet handle to extend it and then the O2 sensor came off pretty quick. From putting up the vehicle on the stands to the testdrive, it took me about 4 hrs to replace the sensor. But now I know I can do it within an hour. Thank you very much you guys for all the info that you have provided on this site. This is all very very helpful. Thanks a million for saving me big bucks and having the satisfaction of doing the job myself.
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Old 11-17-2008, 08:17 PM   #15 (permalink)
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Good deal, glad you were able to solve the problem :)
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