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Old 01-25-2007, 12:11 AM   #1
fenix_black
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Default Need help FAST o2 sensor problem and due for insp!

Ok heres the deal... I have a 2005 RS and I HAD OBX headers on it and a wrx axelback with no other mods... check engine light came on... p0131 bank 1 02 low voltage so I drove the car for awhile while I was debating what to do about it. I took the headers back off and put the stock ones back on to make the light go away so I could pass emissions... well it comes back on after about 5 miles... same code. Here is the bigger problem of it... car is still under warranty BUT I had to lengthen the wires for the rear o2 sensor so it could reach it's bung. I have been trying to figure out what to do about all this and i just dumped $500 on books for school this semester. I have been trying to find info on the "resistor fix" but im not sure if this will even work for the bank 1 sensor. I reeeeally cant afford $260 for a new sensor and I'm thinking the dealership will decline because of the wires... WHAT DO I DO!! the car is due by the end of the month and cops here suck... please someone help me out, any info is appreciated thanks in advance!
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Old 01-25-2007, 12:27 AM   #2
Absubtle
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Quote:
Originally Posted by fenix_black View Post
Ok heres the deal... I have a 2005 RS and I HAD OBX headers on it and a wrx axelback with no other mods... check engine light came on... p0131 bank 1 02 low voltage so I drove the car for awhile while I was debating what to do about it. I took the headers back off and put the stock ones back on to make the light go away so I could pass emissions... well it comes back on after about 5 miles... same code. Here is the bigger problem of it... car is still under warranty BUT I had to lengthen the wires for the rear o2 sensor so it could reach it's bung. I have been trying to figure out what to do about all this and i just dumped $500 on books for school this semester. I have been trying to find info on the "resistor fix" but im not sure if this will even work for the bank 1 sensor. I reeeeally cant afford $260 for a new sensor and I'm thinking the dealership will decline because of the wires... WHAT DO I DO!! the car is due by the end of the month and cops here suck... please someone help me out, any info is appreciated thanks in advance!
Dude, you just stated you have to lengthen the wiring. AND the main reason for a low voltage CODE, is an open in the signal wire! SO why not check the obvious and perhaps re-try wiring it. Perhaps solder and shrink wrap the connections. That is a free way to make sure, your sensor is good. Unless you have a multi-meter (that is fast enough) to check the signal voltage.
Absubtle
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PS- Right off hand, you sure it doesn't mention that your heater voltage is too low. Can't look the code, just yet. I am assuming your signal voltage is low.
Also the "resistor fix", is for the secondary Oxygen sensor, which has a very small operating voltage window. Your code is for bank 1, which will be your primary oxygen sensor. The important one, for you computer to adjust your, closed loop, air/fuels.

Last edited by Absubtle; 01-25-2007 at 12:32 AM. Reason: also...
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Old 01-25-2007, 12:37 AM   #3
silver2004impreza
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The "resistor fix" you're talking about is a simple one. All you have to do is go to Radio Shack and ask them for a 1 mega-ohm resistor, then you wire that resistor into the signal wire of your O2 sensor (I can't remember which wire that is though). Technically the resistor fix is for the downstream sensor if you're running either no cats, or a high-flow one.

However, putting a resistor in line with your sensor is the last thing you want to do at the moment. You've already got low voltage according to the P0131 code, and putting a resistor in the system will lower that voltage even more. I'd definetly do what Absubtle suggested and double check the wires, and if that doesn't fix the problem, you may have to bite the bullet and buy a new sensor. You can try using one of the "universal" O2 sensors, as they're considerably cheaper than the OEM sensors, but you run the risk of the "universal" sensor not working. That's what happened to me anyway. I hope you get it figured out.

Brian
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Old 01-25-2007, 01:52 AM   #4
SiFuSpEc
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i think the best chance you have is to buy a new front o2 sensor, that seems to be end all solution.

other wise, get a tactrix cable, enginuity/ecuflash, and erase the code forever but beware you need something to monitor your front o2 and should only be a temporary fix
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Old 01-25-2007, 04:07 PM   #5
fenix_black
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Quote:
Originally Posted by Absubtle View Post
Dude, you just stated you have to lengthen the wiring. AND the main reason for a low voltage CODE, is an open in the signal wire! SO why not check the obvious and perhaps re-try wiring it. Perhaps solder and shrink wrap the connections. That is a free way to make sure, your sensor is good. Unless you have a multi-meter (that is fast enough) to check the signal voltage.
Absubtle
CO
PS- Right off hand, you sure it doesn't mention that your heater voltage is too low. Can't look the code, just yet. I am assuming your signal voltage is low.
Also the "resistor fix", is for the secondary Oxygen sensor, which has a very small operating voltage window. Your code is for bank 1, which will be your primary oxygen sensor. The important one, for you computer to adjust your, closed loop, air/fuels.
I lengthened the wires to the rear one and when I did it i soldered and shrinked everything... do you think the dealer will decline me?
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Old 01-25-2007, 04:11 PM   #6
fenix_black
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[quote=SiFuSpEc;16801858}
other wise, get a tactrix cable, enginuity/ecuflash, and erase the code forever but beware you need something to monitor your front o2 and should only be a temporary fix[/QUOTE]

Can you tell me some more about this?

Thanks everyone
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Old 01-25-2007, 04:30 PM   #7
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yes if you messed with the sensor the dealer will decline you, if that is the issue... if the code is being cause from something else unmodified you would be ok
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Old 01-25-2007, 06:23 PM   #8
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Don't waste time and money on things that "might" fix the problem. I had the exact same code (p0131) a month ago and after replacing the front 02 sensor all has been solved.
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Old 01-26-2007, 03:49 AM   #9
Tim Sanderson
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I don't see an alternative to just replacing the sensor. Are you sure it
s 260$ for the sensor?
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Old 01-26-2007, 09:16 AM   #10
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Quote:
Originally Posted by Tim Sanderson View Post
I don't see an alternative to just replacing the sensor. Are you sure it
s 260$ for the sensor?
Yea i'm sure
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Old 01-26-2007, 10:30 AM   #11
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as others said why not just try to take it apart and rewire it, than reset the ecu and cross your fingers
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Old 01-26-2007, 01:25 PM   #12
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He is having problems with the front sensor. He modified the rear sensor.

I would follow sc00ters advice.
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Old 02-02-2007, 09:53 AM   #13
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Quote:
Originally Posted by fenix_black View Post
I lengthened the wires to the rear one and when I did it i soldered and shrinked everything... do you think the dealer will decline me?
I hope so, that's not what warranties are for. Buy a new front sensor, either the appropriate generic one, or try one of the many online dealers that sell for less than your local.
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Old 05-05-2008, 05:12 PM   #14
fenix_black
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so, i now have another problem, and since it is relation to this original problem i figured i would just continue in this thread...

well i took sc00ters advice, got a new front o2 sensor and returned to the stock headers.... everything went fine, no more code but now the code is back with the stock headers! The only mod left to my exhaust is an axle back which should have nothing to do with this. I removed the sensor and the tip of it was completely black, so i removed the headers and the inside is completely black so i'm thinking my cats are now completely blocked and this is what caused the code again....

my (possible) plan is to go back to the OBX headers which i USED to be running catless and get universal cat to put in place of the little resonator thing the OBX's came with, and replace both front and rear o2 sensors just to be safe....

my question is, can this setup be run on an '05 (OBX-cat-stock mid pipe-axel back) WITHOUT the need for a tune? im thinking the lack of tune is what has started this whole mess and i just want it to be over... so any input would be much appreciated! thanks in advance
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Old 05-05-2008, 05:14 PM   #15
fenix_black
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oh and once again.. car is due for inspection hahaha figures the timing is perfect....
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Old 05-05-2008, 05:19 PM   #16
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well id be more worrysome of bringing the car for inspection with the obx headers than anything due to the modded cat section, not sure how strict your area is

worse comes to worse borrow a friends sensor to pass than fix your issue
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Old 05-06-2008, 12:29 AM   #17
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your obx headers doesn't HAVE a cat section. It's a REPLACEMENT. It's just a resonator. You need to BUY a generic hi-flow cat and weld that IN PLACE of the resonator for you to have any semblance of a catalytic converter.

That being said, you may have fouled up the sensors when you were running cat-less OR when you installed the headers. It happens.

Stop making it more complicated than it really is and just buy a new sensor. Even the generic ones from autozone will work fine.
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Old 05-06-2008, 01:31 AM   #18
fenix_black
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the car throws the code after a few miles of driving, even on a new sensor straight from the dealer, i have tried that, twice..
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Old 05-06-2008, 01:34 AM   #19
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i love SC... no inspections...
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Old 05-06-2008, 08:30 AM   #20
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Quote:
Originally Posted by rougeben83 View Post
your obx headers doesn't HAVE a cat section. It's a REPLACEMENT. It's just a resonator. You need to BUY a generic hi-flow cat and weld that IN PLACE of the resonator for you to have any semblance of a catalytic converter.

That being said, you may have fouled up the sensors when you were running cat-less OR when you installed the headers. It happens.

Stop making it more complicated than it really is and just buy a new sensor. Even the generic ones from autozone will work fine.



did you even read what he put in post 14?
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