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Old 01-03-2013, 07:04 AM   #1
subaru_steve
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Default P0031 & P0037 on '04 WRX

Car started with a P0031 a few days ago. I cleared it and when I saw the check engine light come on I checked it again to find I now had both a P0031 and P0037. This morning I cleared my ECU again and as soon as the car started up the check engine light was on and both codes were present.

The car has been acting a little funny in that the RPMs drop when I put in my clutch. From what I can tell I do need a new front O2 sensor, but why would that trigger both front and rear heater circuits?

Vehicle:2004 Subaru WRXx

Mods:
Stage II @ 93 Oct via Cobb AP
TurboXS Turboback exhaust
STi Up pipe
K&N Typhoon Intake

Car has had all the above mods on for at least a year and most are 2 years. So its nothing recent that I did that changed the setup. I heard about checking fuses under the glove box but couldn't see any and I think that is only on 2008+. I am going to do my oil change tonight and want to take a look at my harnesses down there and see if anything looks loose or damaged, would I be safe to change out the front O2 while I'm down there?

Thanks!
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Old 01-03-2013, 12:24 PM   #2
Aaron'z 2.5RS
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o2 sensors go bad, as does the front "o2" (an exhaust temp sensor really) over time...

This is why mileage suffers over time a lot of the time... it's the final say to the ECU on how the engine is running... Being that you're getting codes randomly, my guess is they are starting to fail..

If it was just dead fail, I'd be looking at the harness and whatnot, but random codes says normal dieing sensors to me... (I am but one person mind you)

Any other PM work you can think of that's not been done? plugs? fuel filter? IACV clean? Check for vacuum/boost leaks? ...
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Old 01-03-2013, 04:16 PM   #3
subaru_steve
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Quote:
Originally Posted by Aaron'z 2.5RS View Post
o2 sensors go bad, as does the front "o2" (an exhaust temp sensor really) over time...

This is why mileage suffers over time a lot of the time... it's the final say to the ECU on how the engine is running... Being that you're getting codes randomly, my guess is they are starting to fail..

If it was just dead fail, I'd be looking at the harness and whatnot, but random codes says normal dieing sensors to me... (I am but one person mind you)

Any other PM work you can think of that's not been done? plugs? fuel filter? IACV clean? Check for vacuum/boost leaks? ...
Well the rear is technically not "on" since the AccessPort gives a false reading for that one.

Plugs were replaced this summer with NGK iridium's, fuel filter as well, IACV cleaned a month after plugs and filters when it made the car stall out a few times, I am hitting target boost and so far I'm not noticing any signs of boost leak.

I work at Advance Auto and get a discount, I think I'll just grab one already and change the front.
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Old 01-04-2013, 08:24 PM   #4
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Quote:
Originally Posted by subaru_steve View Post

Well the rear is technically not "on" since the AccessPort gives a false reading for that one.

Plugs were replaced this summer with NGK iridium's, fuel filter as well, IACV cleaned a month after plugs and filters when it made the car stall out a few times, I am hitting target boost and so far I'm not noticing any signs of boost leak.

I work at Advance Auto and get a discount, I think I'll just grab one already and change the front.
The AP gives a false reading for what code?

I currently am running a extremely similiar set up
(Stage2 93 oct
Helix high flow cat dp
Cobb cat back)
And my vehicle recently poped up the code P0031

Also on warm start up she will bog very often and stalled twice so far but only on warm start up (drove, parked, came back 30min later)

I was speaking to someone else on the forum about it and he said he replaced the whole throttle body and it fixed the bogging problem nd as for O2 sensor I was reccomended to start with intake and make my way to the upipe, ill clean the maf sensor and mybe do a seafoam run.
Hopefully the problem will get solved
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Old 01-04-2013, 09:07 PM   #5
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Quote:
Originally Posted by Aaron'z 2.5RS View Post
o2 sensors go bad, as does the front "o2" (an exhaust temp sensor really) over time...


the front o2 is nothing like any sort of exhaust temp sensor......in no way...it IS a feedback 'narrow band' o2 sensor and have NO temperature input or output

there are 3 sensors in the 2.0 exhaust

in this order
front o2 in the passengers manifold
egt in the up pipe just below the turbo
rear o2 at the aft end of the dp


now....many have confused the egt for an o2 sensor which it is NOT and the front o2 and egt are NOT interchangeable

there IS a fuse for the heater circuit that may be bad
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Old 01-05-2013, 03:53 AM   #6
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Quote:
Originally Posted by Uncle Scotty View Post

there IS a fuse for the heater circuit that may be bad
Is that for both situations or just the OP's
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Old 01-05-2013, 07:54 PM   #7
subaru_steve
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So I plugged my AP in and using live data looked at my AFR, it sits at 14.7, no deviation. That tells me either the wires burnt through, the sensor has failed, or something isn't connected.

I looked at the gray connector near the passanger strut tower and pulled it apart, no corrosion, no frayed wires or anything. Next will be tomorrow when I do my oil change I'm taking the passenger wheel off to look at the sensor from inside the wheel well and see what I can find.

Otherwise looks like I'm getting a new sensor, anyone know an online vendor selling them for under $140? I found most places sell them at $215 and I know someone has to have them for a bit cheaper.
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Old 01-05-2013, 08:25 PM   #8
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Quote:
Originally Posted by subaru_steve View Post
So I plugged my AP in and using live data looked at my AFR, it sits at 14.7, no deviation. That tells me either the wires burnt through, the sensor has failed, or something isn't connected.

I looked at the gray connector near the passanger strut tower and pulled it apart, no corrosion, no frayed wires or anything. Next will be tomorrow when I do my oil change I'm taking the passenger wheel off to look at the sensor from inside the wheel well and see what I can find.

Otherwise looks like I'm getting a new sensor, anyone know an online vendor selling them for under $140? I found most places sell them at $215 and I know someone has to have them for a bit cheaper.
Let me know what you find and I shall do the same, im in the same situation as you right now -_-
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Old 01-05-2013, 08:28 PM   #9
04sedantyson
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my 04 did this around 120,000, replaced front o2 and it was fine
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Old 01-05-2013, 08:42 PM   #10
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Mines only sitting at 85k -_-
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Old 01-05-2013, 08:50 PM   #11
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Quote:
Originally Posted by tjmmason93 View Post
Is that for both situations or just the OP's
Quote:
Originally Posted by tjmmason93 View Post
Mines only sitting at 85k -_-

irrelevant
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Old 01-05-2013, 09:50 PM   #12
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irrelevant
I Guess start with cheapest options and move upward
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Old 03-18-2013, 12:09 PM   #13
Aloretoc
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Quote:
Originally Posted by subaru_steve View Post
So I plugged my AP in and using live data looked at my AFR, it sits at 14.7, no deviation. That tells me either the wires burnt through, the sensor has failed, or something isn't connected.

I looked at the gray connector near the passanger strut tower and pulled it apart, no corrosion, no frayed wires or anything. Next will be tomorrow when I do my oil change I'm taking the passenger wheel off to look at the sensor from inside the wheel well and see what I can find.

Otherwise looks like I'm getting a new sensor, anyone know an online vendor selling them for under $140? I found most places sell them at $215 and I know someone has to have them for a bit cheaper.
BUMP for an answer!!!

im in the same situation as the OP i have 2011 wrx with 25k miles in her.
I just had both o2 sensors replaced by the dealer. Front o2 and the o2 in the downpipe. As soon as i start her up i get both cel codes p0031 and p0037.
When i connect my AP to read the sensor ratio for the narrowband, sometimes it just stays at 14.7 and doesnt move at all but after driving for a while it starts reading but it doesnt seem to be accurate. It will read around 14.4 crusing speed (matches my wideband sensor) but when i go into boost the lowest it will go is 13.6 and when i let go of the throtle the highest it will go is 15.6 (my wideband reads 10.8 when accelerated and "---" when let go of the accelerator)
I dont know what this problem could be.
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Old 03-18-2013, 12:18 PM   #14
tjmmason93
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Quote:
Originally Posted by Aloretoc View Post
BUMP for an answer!!!

im in the same situation as the OP i have 2011 wrx with 25k miles in her.
I just had both o2 sensors replaced by the dealer. Front o2 and the o2 in the downpipe. As soon as i start her up i get both cel codes p0031 and p0037.
When i connect my AP to read the sensor ratio for the narrowband, sometimes it just stays at 14.7 and doesnt move at all but after driving for a while it starts reading but it doesnt seem to be accurate. It will read around 14.4 crusing speed (matches my wideband sensor) but when i go into boost the lowest it will go is 13.6 and when i let go of the throtle the highest it will go is 15.6 (my wideband reads 10.8 when accelerated and "---" when let go of the accelerator)
I dont know what this problem could be.
I would suggest resting the ecu... If you just recently had the 02 sensors replaced? Maybe its acting up. And if its still under warranty have subaru do it lmao
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Old 03-18-2013, 12:28 PM   #15
Aloretoc
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Quote:
Originally Posted by tjmmason93 View Post
I would suggest resting the ecu... If you just recently had the 02 sensors replaced? Maybe its acting up. And if its still under warranty have subaru do it lmao
ECU was reset and both sensors were replaced by the dealer.

But as soon as i crank up the car the codes come back up almost immediately
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Old 03-18-2013, 02:03 PM   #16
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Quote:
Originally Posted by Aloretoc View Post

ECU was reset and both sensors were replaced by the dealer.

But as soon as i crank up the car the codes come back up almost immediately
If the dealership did it then call them back and tell them they screwed something up. I mean off the top of my head I can't think of any resolution unless the cords are damaged and switching on and off somewhere in the feed back to the ecu. But it wouldn't explain how it starts to work when u drive for a while. I would try and get it to work then clear the codes with ur AP and then see how long it takes for the codes to appear again. Its gotta be in the wiring right?
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Old 03-18-2013, 02:22 PM   #17
Aloretoc
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Quote:
Originally Posted by tjmmason93 View Post

If the dealership did it then call them back and tell them they screwed something up. I mean off the top of my head I can't think of any resolution unless the cords are damaged and switching on and off somewhere in the feed back to the ecu. But it wouldn't explain how it starts to work when u drive for a while. I would try and get it to work then clear the codes with ur AP and then see how long it takes for the codes to appear again. Its gotta be in the wiring right?
I can't demand too much from the dealer as they replaced both sensors as a favor if you might say... (My car is pro tuned stage 2)
I checked the fuses and everything seems to be fine, my guess is there might be a connector somewhere loose nor making proper connection... Idk man... It's driving me nuts...

Last edited by Aloretoc; 03-18-2013 at 02:35 PM.
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Old 03-20-2013, 10:36 PM   #18
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i got similar code p0030 but i cleared it and it never came back since then.
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Old 03-21-2013, 05:40 PM   #19
subaru_steve
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Hey the my thread is alive again!

So I have purchased a new front O2 sensor, just waiting for the temp to get above freezing so I can stand to be outside next to my car for more than 10 minutes to do this. I'll see if it fixes it!
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Old 03-21-2013, 07:01 PM   #20
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Quote:
Originally Posted by subaru_steve View Post
Hey the my thread is alive again!

So I have purchased a new front O2 sensor, just waiting for the temp to get above freezing so I can stand to be outside next to my car for more than 10 minutes to do this. I'll see if it fixes it!
Good luck my friend
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Old 03-21-2013, 07:32 PM   #21
Aloretoc
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Quote:
Originally Posted by subaru_steve View Post
Hey the my thread is alive again!

So I have purchased a new front O2 sensor, just waiting for the temp to get above freezing so I can stand to be outside next to my car for more than 10 minutes to do this. I'll see if it fixes it!
I'm taking mine to the dealer tomorrow... I'll keep you guys posted what it could be (if they can find the reason)
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Old 03-22-2013, 01:04 PM   #22
Aloretoc
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Quote:
Originally Posted by Aloretoc View Post

I'm taking mine to the dealer tomorrow... I'll keep you guys posted what it could be (if they can find the reason)
So the dealer came back saying it was a fuse... They tested it and everything is fine now -_-
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Old 03-24-2013, 10:37 PM   #23
adecan
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Hey there,

I had the p0031 code and I installed a new sensor (denso 234-9011) but the code still on.

I'm kinda neewe here so I need some extra help. I will follow your suggestions and sharing the results. Please don't leave me alone. I'm in Venezuela and the nearest dealer is about 500 mile from my city.

Thanks in advance
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Old 03-24-2013, 10:59 PM   #24
Aloretoc
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Quote:
Originally Posted by adecan View Post
Hey there,

I had the p0031 code and I installed a new sensor (denso 234-9011) but the code still on.

I'm kinda neewe here so I need some extra help. I will follow your suggestions and sharing the results. Please don't leave me alone. I'm in Venezuela and the nearest dealer is about 500 mile from my city.

Thanks in advance
Check your fuses
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Old 04-03-2013, 12:19 PM   #25
Aloretoc
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Quote:
Originally Posted by adecan View Post
Hey there,

I had the p0031 code and I installed a new sensor (denso 234-9011) but the code still on.

I'm kinda neewe here so I need some extra help. I will follow your suggestions and sharing the results. Please don't leave me alone. I'm in Venezuela and the nearest dealer is about 500 mile from my city.

Thanks in advance
Any updates?
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