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Discussion Starter · #1 ·
Over the past like 3 weeks, I've had P0133 come up again and again. Ive replaced the upper O2 sensor, and cleaned the MAF. Cleaning the MAF kept the light off for a highway of about 100 miles, but as soon as I let her idle it came right back. I reset the ECU today, and it stayed off for a bit as well, until I got into a drive through and let it idle a lot. I don't hear any exhaust leaks, but I was planning checking the manifold tomorrow with the soapy water. I have a completely aftermarket exhaust, with a spacer on the upper and lower O2 sensors. Any ideas are much appreciated.

The only other mod I have is a CAI mostly just for the meme. I did also notice soot on my bumper above my muffler which is usually a good sign its running rich right?
 

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Take the damn spacer off of the upper o2 sensor...dude wtf...the upper is for the a/f ratio....
 

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Discussion Starter · #3 ·
Take the damn spacer off of the upper o2 sensor...dude wtf...the upper is for the a/f ratio....
I was under the impression that would give me a code for not having the precat on anymore. Is that not the case then?
 

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It is not, the spacer is for the lower one and for emissions...
 

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2005 Sentra SE-R spec-v
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Alright well I'll take that off then haha thank you
The precat O2 sensor measures the air fuel ratio coming from your engine and forms a baseline for the amount of oxygen in your exhaust stream. When it goes through a warmed up cat, the chemical reaction creates more oxygen that the second sensors should read. The spacer is to simulate that additional oxygen. If you space both, they'll have the same reading and the ECM will think you're running absurdly lean. That's setting your fault.
 
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