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Old 03-27-2011, 11:52 AM   #1
Boyka67
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Upstream and downstream 02 sensor swap?

I kinda jacked up my rear o2 sensor threading when removing it for my new header. now it wont screw into the header and I'm running lean now. question is, is it possible to use the front on the rear? i have the tune for it and the extension for it so length is no problem. they both have the same harness, so i was wondering if i could just wire up the good threaded o2 sensor to the harness i need, plug it in and be good to go? I don't want to start cutting yet, but if anyone can please help me i would appreciate it. Oh and for a new one it would cost me like $110 at an auto parts store, so I'm trying to avoid dishing out a crap load of money if i can do this. thanks!


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Old 03-27-2011, 11:54 AM   #2
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the rear 02 shouldn't make you run lean, i thought it only checked the function of the catalyst. the front 02 is what tells the computer info on the A/F. how do you know its running lean? a CEL or do you have a wideband?
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Old 03-27-2011, 11:59 AM   #3
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I checked the cel and it says o2 sensor malfunction lean or something like that
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Old 03-27-2011, 12:00 PM   #4
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^^Correct. The rear O2 only monitors cat health. If this is a newly installed header, you will get a CEL as the rear O2 sensor is no longer seeing a difference between what it and the front O2 sees as there is no cat anymore. You can either do an O2 cheater trick, or get a tune to delete it altogether.
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Old 03-27-2011, 12:02 PM   #5
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Quote:
Originally Posted by Boyka67 View Post
I checked the cel and it says o2 sensor malfunction lean or something like that
did it mention which one? its probably throwing a CEL because you removed that mani-cat or whatever you want to call it.
edit: got beat to it.
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Old 03-27-2011, 12:07 PM   #6
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i checked again right now and it says P2195 O2 sensor signal biased/stuck lean (B1,S1)

I do have the tune, but the cel still came on and my mpg is horrible now...i got ~30 before i installed the new fswerks header, and after, it threw the cel and now i get like 17mpg or is that normal?
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Old 03-27-2011, 12:10 PM   #7
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not normal. did you try to clean your sensor at all? sounds like your 1st is no longer working or it was not completely seated into the connector.
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Old 03-27-2011, 12:16 PM   #8
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maybe i screwed it up...i put the o2 sensor on that was on the cat on the new header and took off the one on the old header because it didnt fit the extension that came with the header, the one on the old cat did. It was the o2 sensor with the blue harness if that helps. should i have put the one with the gray harness on the header?
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Old 03-27-2011, 12:31 PM   #9
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not normal. did you try to clean your sensor at all? sounds like your 1st is no longer working or it was not completely seated into the connector.
well real problem is the threading is screwed up, so it doesnt sit properly in the header and falls out sometimes. i was wondering if i could use the other o2 sensor i had laying around since it has good threading on it. would it do the same thing.
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Old 03-27-2011, 12:59 PM   #10
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The O2 sensors will not swap between up stream an downstream, the plugs are differant, and yes you should have used the blue harness it is the upstream.
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