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Old 09-10-2010, 11:04 PM   #1
The G.O.A.T.
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Default o2 problems

I think my o2 sensor is going is there a way to clean it?
Also was wondering if there is any preventative maintenance that I should do as I do not have a cat and I Get a lot of carbon buildup.
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Old 09-11-2010, 12:10 AM   #2
formula91
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Once it's going, it's on it's way out, there's little you can do.

You can try taking a propane torch to it to burn off any carbon residues, but that's about it.
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Old 09-11-2010, 02:32 AM   #3
williaty
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Heavy carbon buildup is normal, especially on teh stock tune. When it comes time to replace the O2 sensor, be sure to use a Denso from Subaru, not a Bosch from the parts store. For whatever reason, a number of 05+ cars have had poor sensor life with the Bosch sensors.
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Old 09-12-2010, 09:47 PM   #4
Sir-Knight
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subarugenuineparts has the oem denso for pretty cheap, even with the us/can conversion, did that this summer as well.
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Old 09-13-2010, 12:08 AM   #5
The G.O.A.T.
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Now i have a P0137 code? is that the front or the rear???
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Old 09-13-2010, 12:10 AM   #6
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Rear. But there's a 50-50 chance the ECU has concluded the rear is broken due to the fact that the front is giving bad data. You have to wait it out until it throws enough codes to signal that it's made up its mind.
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Old 09-13-2010, 05:58 AM   #7
The G.O.A.T.
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Well it is a good thing I got the front replaced then right? Then it is defiantly the rear and I could just turn that one off with my AP right and no harm done?
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Old 09-13-2010, 08:36 AM   #8
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Nope. Turning off the rear O2 sensor codes will result in weird and erratic behavior by the ECU. You need two properly functioning, properly installed O2 sensors in a 05+ car.
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Old 09-14-2010, 03:11 PM   #9
The G.O.A.T.
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even if i don't have a cat? and have a custom tune?
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Old 09-14-2010, 03:12 PM   #10
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Yes. That's the fun and wonder of owning a 32bit ECU.
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Old 09-15-2010, 02:29 AM   #11
The G.O.A.T.
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thanks Mr. Williaty. I guess the cat will be going back in soon
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Old 09-15-2010, 03:49 AM   #12
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Oh, you can leave the cat out if you want. It doesn't affect the HP of the car one way or the other, nor does the ECU really care. If you leave the cat out, you need to disable the P0420 DTC via ECU reflash (tuning). The P0420 is not a rear-O2 sensor code and does not affect the way the ECU behaves. You will need to leave both the front and rear O2 sensors properly installed in the exhaust stream, though.
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Old 09-15-2010, 02:59 PM   #13
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Quote:
Originally Posted by williaty View Post
Rear. But there's a 50-50 chance the ECU has concluded the rear is broken due to the fact that the front is giving bad data. You have to wait it out until it throws enough codes to signal that it's made up its mind.
How long is waiting it out? For example, MY07 WRX has tossed the p0137 (and only this code) once a week for the past few weeks.

Would you say that is waiting long enough?

I see the OE replacement (Denso) is only $67 w/out shipping at sparkplug.com
That isn't to painful I suppose.
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Old 09-15-2010, 03:10 PM   #14
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The problem is that as long as it's only tossing out the P0137, there's no way to be sure which sensor is actually borked. Basically, the P0137 means that the rear O2 sensor output a low voltage for too long of a time. This can mean the rear O2 has failed and stuck low. However, it can also mean that the front O2 has failed and has caused the AFR to change to the point the rear O2 sensor is legitimately reading low. Once you get a supporting code, such as another failure code for the rear O2, or a failure for the front O2, it becomes easier to figure out which is really pissed off.

In your case, it might be worth buying a rear anyway to see what happens if it goes on that long. I have a hard time believing that the price you found is actually the right part though, as the rear O2 sensor is actually even more expensive than the front one.
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Old 09-15-2010, 05:40 PM   #15
flimflamman
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Yep I thought that price was low too, but this is what a search yields at sparkplug.com (02 sensors for 07 wrx)

Make: SUBARU
Model: IMPREZA - WRX TR
Year: 2007
Engine: H4 - 2.5L - FI - EJ255-T - GAS

Denso AIR/FUEL SENSOR stock#234-9120 part#234-9120 Front Sale: $104.40 $313.78
Denso OE identical O2 sensor stock#234-4732 part#234-4732 Rear Sale: $66.66 $213.53
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Old 09-15-2010, 05:44 PM   #16
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The Subaru part number for your application is 22690AA520. My wholesale price from a Subaru dealer on that is $115. From a 3rd party, it's still $90. It makes me wonder if they're cutting corners on the part at sparkplug.
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Old 09-15-2010, 06:01 PM   #17
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Hmmmm... I'll probably end up kicking myself for doing it, but I am going to give them a try.
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Old 09-16-2010, 12:10 PM   #18
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I just bought both O2 sensors fro my 02 TS. Bonds Auto carries Denso parts and costs half what you would pay at the dealership. Cost me $230 would have been over $400 at the dealer.
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