o2 problems

The G.O.A.T. · 09-10-2010, 10:04 PM

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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formula91 · 09-10-2010, 11:10 PM

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.

williaty · 09-11-2010, 01:32 AM

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.

Sir-Knight · 09-12-2010, 08:47 PM

subarugenuineparts has the oem denso for pretty cheap, even with the us/can conversion, did that this summer as well.

The G.O.A.T. · 09-12-2010, 11:08 PM

Now i have a P0137 code? is that the front or the rear???

williaty · 09-12-2010, 11:10 PM

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.

The G.O.A.T. · 09-13-2010, 04:58 AM

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?

williaty · 09-13-2010, 07:36 AM

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.

The G.O.A.T. · 09-14-2010, 02:11 PM

even if i don't have a cat? and have a custom tune?

williaty · 09-14-2010, 02:12 PM

Yes. That's the fun and wonder of owning a 32bit ECU.

The G.O.A.T. · 09-15-2010, 01:29 AM

thanks Mr. Williaty. I guess the cat will be going back in soon

williaty · 09-15-2010, 02:49 AM

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.

flimflamman · 09-15-2010, 01:59 PM

Quote:

Originally Posted by williaty

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.

williaty · 09-15-2010, 02:10 PM

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.

flimflamman · 09-15-2010, 04:40 PM

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

williaty · 09-15-2010, 04:44 PM

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.

flimflamman · 09-15-2010, 05:01 PM

Hmmmm... I'll probably end up kicking myself for doing it, but I am going to give them a try.

ibanez24_7 · 09-16-2010, 11:10 AM

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.

09-10-2010, 10:04 PM	#1
The G.O.A.T. Scooby Newbie Member#: 149724 Join Date: May 2007 Chapter/Region: W. Canada Location: Calgary Alberta, Canada Vehicle: 1999 leggy gt 5speed Blood red	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. * Registered users of the site do not see these ads.

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09-10-2010, 11:10 PM	#2
formula91 Scooby Specialist Member#: 102984 Join Date: Dec 2005 Chapter/Region: MWSOC Location: Northbrook, IL Vehicle: 2005 2.5RS 4EAT Platinum Silver	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.

09-11-2010, 01:32 AM	#3
williaty Scooby Guru Member#: 71092 Join Date: Sep 2004 Chapter/Region: MWSOC Location: Delaware County, Ohio Vehicle: 2005 2.5RS Wagon Regal Blue Pearl	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.

09-12-2010, 08:47 PM	#4
Sir-Knight Scooby Specialist Member#: 73636 Join Date: Nov 2004 Chapter/Region: E. Canada Location: the 'wa, ontario, canada Vehicle: 2007 Impreza 2.5i SE newport blue pearl	subarugenuineparts has the oem denso for pretty cheap, even with the us/can conversion, did that this summer as well.

09-12-2010, 11:08 PM	#5
The G.O.A.T. Scooby Newbie Member#: 149724 Join Date: May 2007 Chapter/Region: W. Canada Location: Calgary Alberta, Canada Vehicle: 1999 leggy gt 5speed Blood red	Now i have a P0137 code? is that the front or the rear???

09-12-2010, 11:10 PM	#6
williaty Scooby Guru Member#: 71092 Join Date: Sep 2004 Chapter/Region: MWSOC Location: Delaware County, Ohio Vehicle: 2005 2.5RS Wagon Regal Blue Pearl	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.

09-13-2010, 04:58 AM	#7
The G.O.A.T. Scooby Newbie Member#: 149724 Join Date: May 2007 Chapter/Region: W. Canada Location: Calgary Alberta, Canada Vehicle: 1999 leggy gt 5speed Blood red	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?

09-13-2010, 07:36 AM	#8
williaty Scooby Guru Member#: 71092 Join Date: Sep 2004 Chapter/Region: MWSOC Location: Delaware County, Ohio Vehicle: 2005 2.5RS Wagon Regal Blue Pearl	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.

09-14-2010, 02:11 PM	#9
The G.O.A.T. Scooby Newbie Member#: 149724 Join Date: May 2007 Chapter/Region: W. Canada Location: Calgary Alberta, Canada Vehicle: 1999 leggy gt 5speed Blood red	even if i don't have a cat? and have a custom tune?

09-14-2010, 02:12 PM	#10
williaty Scooby Guru Member#: 71092 Join Date: Sep 2004 Chapter/Region: MWSOC Location: Delaware County, Ohio Vehicle: 2005 2.5RS Wagon Regal Blue Pearl	Yes. That's the fun and wonder of owning a 32bit ECU.

09-15-2010, 01:29 AM	#11
The G.O.A.T. Scooby Newbie Member#: 149724 Join Date: May 2007 Chapter/Region: W. Canada Location: Calgary Alberta, Canada Vehicle: 1999 leggy gt 5speed Blood red	thanks Mr. Williaty. I guess the cat will be going back in soon

09-15-2010, 02:49 AM	#12
williaty Scooby Guru Member#: 71092 Join Date: Sep 2004 Chapter/Region: MWSOC Location: Delaware County, Ohio Vehicle: 2005 2.5RS Wagon Regal Blue Pearl	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.

09-15-2010, 02:10 PM	#14
williaty Scooby Guru Member#: 71092 Join Date: Sep 2004 Chapter/Region: MWSOC Location: Delaware County, Ohio Vehicle: 2005 2.5RS Wagon Regal Blue Pearl	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.

09-15-2010, 04:40 PM	#15
flimflamman Scooby Specialist Member#: 147328 Join Date: Apr 2007 Chapter/Region: SCIC Location: Glendale, CA Vehicle: 2007 Silver WRX w/VF39	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

09-15-2010, 04:44 PM	#16
williaty Scooby Guru Member#: 71092 Join Date: Sep 2004 Chapter/Region: MWSOC Location: Delaware County, Ohio Vehicle: 2005 2.5RS Wagon Regal Blue Pearl	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.

09-15-2010, 05:01 PM	#17
flimflamman Scooby Specialist Member#: 147328 Join Date: Apr 2007 Chapter/Region: SCIC Location: Glendale, CA Vehicle: 2007 Silver WRX w/VF39	Hmmmm... I'll probably end up kicking myself for doing it, but I am going to give them a try.

09-16-2010, 11:10 AM	#18
ibanez24_7 Scooby Newbie Member#: 192322 Join Date: Oct 2008 Location: Springfield, VT Vehicle: 2002 Impreza TS	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.