2006 Sentra SE-R SpecV P2A00

2006 NISSAN SENTRA
60,000 MILES • 4 CYL • FWD • MANUAL
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SPECV
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I have a 2006 Nissan Sentra SE-R Spec-V. Almost immediately upon putting on a Megan Racing header, my car started throwing a P2A00 code. I know this is the primary O2 sensor out of range/out of performance. It is caused by a shift to the lean or rich side for a specified period.

I have replaced BOTH of the O2 sensors with stock Nissan units, but the code remained. I took it to Nissan and they performed an idle air relearn using their Consult-III program. The code stayed off for 120 miles and then reappeared.

I have been unable to find any sort of intake or exhaust leak after attacking the engine bay with carb cleaner.


I'm able to read the voltage given off by both O2 sensors, and the A/F sensor likes to stay around .024V. If I blip the throttle or slow the engine using the transmission, the voltage will go up to sometimes .8V.

Any ideas what could be causing this code, and is the voltage I'm seeing the way it should be?
Apr 25, 2011 at 6:18 PM
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WRENCHTECH
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It sounds like the 0/2 sensor is accurately reporting a lean condition. You could verify that by looking at the long term fuel adaptives and see if they are going rich. You're going to have to get to the bottom of the cause for the lean condition.
Apr 25, 2011 at 7:01 PM
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SPECV
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I agree, the car is running lean. At idle, my long term fuel trim is flatlined at 0%. My short term fuel trim hovers around 14%. When I hold the engine at 1500-2000 RPM, the STFT rises to 20%. Letting my foot off the throttle, the STFT falls to 6%, then rises to the 14% at idle again.

Would this suggest a vacuum leak, or more likely an exhaust leak? Based on everything I can find on this code with my car, it appears that a crack in a header or something similar is to blame.
May 2, 2011 at 7:20 PM