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so does this mean that my 02 sensor is fine? or could that still be the problem? or do i have to find the short first with a volt meter? and how bad is it for me to be driving around with these codes, and that blown fuse?
 

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It may be the sensor, it may not. It may just be a short in the wiring. Check to see if you damaged any wires putting your uppipe in. If you don't mind wasting another fuse. Try putting one in with the o2 disconnected. Then you can isolate the problem.
You also may have a problem with the rear as well. So check all those wires for any damage.


Driving around this way will probably ruin that front O2 sensor if it's even ok now. Without the heater the sensor won't last long. Most likely the car will stay in open loop fueling and the ecu will not be able to make changes to AFR. I would certainly stay out of boost. Biggest hit will probably be fuel economy.
 

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You're not going to be able to test an o2 sensor with a volt meter thet are very tricky to test....
yeah you really need to put a scanner on the car and watcht he 02 values. not sure if the AP has the capability. i doubt the 02 sensor would be the cause of the fuse blowing.
 

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i had the same problem. Subaru South Africa told me it was the sensor that was stuffed. I am now waiting 4 months for this sensor. i just happened to come across this post now. I went to my car checked the fuse...IT WAS BLOWN!!! i changed it, reset the ECU and it is working again!

thanks for the helpful tip. there must be idiots working at this subaru dealership if they didnt know about it, they had my car for a day and couldnt find a blown fuse????lol

thanks guy
 

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Update:

I went down to AZP Installs in Kenilworth (FTW!) and upon inspection of the rear o2 sensor Adam and I had found the notorious frayed wires. Replaced the o2 sensor, followed by the heater circuit fuse and voila no more CEL's and the cars running great! Thanks everyone for your help and an extra big thanks to AZP installs!

-Sean
 

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UPDATE: This works! I have had the p0031 and p0037 codes forever now. I replaced the rear o2 sensor bc it was frayed and the code was still up. The front one looked fine so that left me with a lot of hunting. I check that all the grounds to the engine were good and then began searching the internet for threads w/ this problem. This is the first one mentioning the 2 STUPID fuses under the glove box. I went and got a 20 watt fuse (radioshack didn't have 15) and walllahhh! Check engine light is gone and I can use cruise control again! Everyone with this problem check that dumb fuse first!
 

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Wow, I've been searching for this answer for the past few months!! I also had that damn blown fuse,and it keeps blowing right away. I must have some damaged wires as well I assume. I'll check that out tomorrow.

One question though, our local tuner suggested I try unpluging the rear O2 sensor to see if the fuse stops blowing. If this fixes the problem, he want to just put in an old sensor (to plug the hole) and leave it like that as the rear O2 sensor doesn't do much anyway. I thought I read somewhere that the rear O2 could also affect fueling? Can anyone advise if it's a good idea to do this and just disable the rear O2 CEL codes or does the rear O2 do more than just measure Cat Efficiency.

Thanks guys!
 

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^ im not sure what the second o2 sensor does but I would never just leave it unhooked. Its there for a reason (even if i dont know what reason haha). Try getting a new sensor maybe? or a higher watt fuse (20 watt like me)? Regardless, you should fix the problem and not just put a bandaid on it. just my 2 cents.
 

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It may be the sensor, it may not. It may just be a short in the wiring. Check to see if you damaged any wires putting your uppipe in. If you don't mind wasting another fuse. Try putting one in with the o2 disconnected. Then you can isolate the problem.
You also may have a problem with the rear as well. So check all those wires for any damage.


Driving around this way will probably ruin that front O2 sensor if it's even ok now. Without the heater the sensor won't last long. Most likely the car will stay in open loop fueling and the ecu will not be able to make changes to AFR. I would certainly stay out of boost. Biggest hit will probably be fuel economy.
You described the exact same problem im having right now with my 2011 wrx sedan. Just installed a turboback 3 weeks ago... and a few days ago threw p0031 and p0037. Can runs like dog crap... fuel economy is terrible. Jacked up the car yesterday and found frayed wires on the rear O2. Blowing fuses as well. Ordered a new front O2 sensor from Rock Auto.
 

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This is an old thread, but I found it while searching for this same problem on my 2015 STI that I got two weeks ago with 28k miles. Just today I installed a catted downpipe and on first ride, I got those codes P0031 and P0037. The wires are fine. Nothing frayed, melted, etc. If there's a secret fusebox under the glovebox of this car, I sure can't find it! Was wondering if anybody knew where it's hiding. I dread the idea of taking it to the dealer for this, due to the exhaust.

Thanks.

Rob
 

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That was it. Adding some photos in case anyone else has this. Maybe it'll save them the sleepless night I had dreading running down an electrical short!

Auto part Pipe Fuel line Engine


I'm on a Cobb DP with a Grimspeed heat shield. The heat shield corner is quite sharp. You can see it touching the wire bundle top center of the photo.

Auto part Tire Automotive tire Pipe


Hard to see in the photo, but 2 wires by my finger are nicked. Just enough to ground them out and blow the fuse. Fuse is located (for 15+) in the drivers side fuse box. It's in the black strip on the right side, not labeled but it's the 7th down and the last 15 amp fuse. Mine would blow as soon as you turned the key on. I wrapped the 2 nicked wires in electrical tape. Held the whole wire bundle out of the way with a bit of safety wire. Been running fine with no CEL for 5 days now.
 

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Woo! I'm glad you were able to find it.

I haven't had my intercooler off since then, but next time I do, I'm going to inspect them more closely and see if there's anything I can do to better wrap them. The dealer was who found it for me, and at my request they just tied the wire bundle back and wrapped it with tape as best they could.
 
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