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Old 05-02-2013, 06:11 PM   #1
bbaker80
Scooby Newbie
 
Member#: 41517
Join Date: Aug 2003
Chapter/Region: SWIC
Location: Pittsburgh, PA
Vehicle:
2005 WRX Wagon
WR Blue

Default P0172 Bank 1 Rich CEL

So for starters I've searched and tried a number of things including cleaning the MAF, searching for leaks in the intake, new plugs, checked the fuel pressure reglator, etc. I'm not sure what data to look for to verify if the front O2 sensor is working. I am leaning twoard the O2 sensor as the issue based on what I have found.

The car is an 05 WRX with an MRT CAI, stock exhaust, and UTEC. The Wideband is not currently installed as there is no bung in the stock downpipe, and I am running a tune that has worked for years with this setup so I do not think it is related to the tune. I would normally be running a bellmouth DP with 3" catback but PA requires emissions testing and I need to run the catted exhaust to pass.

I do have a scanner and captured the last time the code came up:
Absolute tps 11.8%
Engine speed 724 rpm
Calculated load 3.1%
Maf 0.84lb/m
Map 11.8"hg
Coolant temp 194
Iintake air temp 50
Ignition advance 11.5
St firm -25.0%
Lt firm -5.5%
O2s12 v 0.000v
St firm12 0.0%

Can anyone confirm this for me? I don't mind spending the $120 for the sensor, I just don't want to be throwing money at issues that I've misdiagnosed.

Thanks,
Bryan
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Old 05-02-2013, 09:37 PM   #2
greenplates
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Join Date: Feb 2010
Chapter/Region: NESIC
Default

So you swapped exhausts back to stock?

either way, that code is an o2 sensor. if you decide to replace it, get one from Subaru. do not get a cheap sensor from auto parts store. totally not worth it
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Old 05-03-2013, 09:07 AM   #3
bbaker80
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Join Date: Aug 2003
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Location: Pittsburgh, PA
Vehicle:
2005 WRX Wagon
WR Blue

Default

The exhaust went back to stock when I moved back east form Las Vegas because I was out of room in the moving truck for extra parts.

Are you saying that in general this code is a result of a failed O2 or are you saying the data from the scanner indicates a failure?
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Old 07-13-2013, 12:46 AM   #4
bbaker80
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Join Date: Aug 2003
Chapter/Region: SWIC
Location: Pittsburgh, PA
Vehicle:
2005 WRX Wagon
WR Blue

Default

So the car has been parked since my last post because I've been too busy to work on it. Yesterday I cleared the code, installed a new front O2 and spark plugs, and today the code is back. Driveability has improved slightly, but I still have hesitation under light loads and I'm not going to pass emissions testing without fixing this. What's next? FPR? MAF? I'm not sure at this point...
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Old 07-15-2013, 05:28 PM   #5
02wrxej208
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Chapter/Region: South East
Location: Pensacola, Florida
Vehicle:
2002 stroked 20g bug
WRB

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i just threw this same CEL, let me know what your fix is please
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Old 07-15-2013, 09:45 PM   #6
bbaker80
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2005 WRX Wagon
WR Blue

Default

Quote:
Originally Posted by 02wrxej208 View Post
i just threw this same CEL, let me know what your fix is please
Have you tried anything yet to resolve the issue? My gut feeling is now that I can rule out the O2 sensor and the plugs all looked okay for 50k and a rich condition that this is probably fuel related. I did have to swap out the fuel pump and filter after the car was parked for a while in Vegas, maybe bits of the old filter were in the line and have damaged the fuel pressure regulator?

I'd love to run my car to the dealership at this point and let them diagnose the issue but the dealer I trust is 70ish miles away and I'm still waiting for the DOT here to get me a replacement license plate. I'm still looking for any suggestions if anyone has seen this before.
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Old 07-24-2013, 02:35 PM   #7
bbaker80
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Join Date: Aug 2003
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Location: Pittsburgh, PA
Vehicle:
2005 WRX Wagon
WR Blue

Default

So last night I decided to unplug the UTEC since at this point the CAI is really the only mod that I need to tune for, and I am relatively sure I have found the issue. The front O2 now has a reading when the scanner is hooked up. I'm just hoping that the UTEC failure hasn't damaged anything else.
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