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2004 Outback Wagon EJ259 - 4EAT
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Discussion Starter #1
I have a 2004 PZEV with the five total O2 sensors. Should the readings for the two front sensors be nearly the same, when being monitored by logging software?
 

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2001 VDC/SC One of a Kind
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Yes. If they are not close to equal in the minimal waveform they have, there may be an issue with combustion or fuel delivery. I have a video of a VDC with a 3.0 that uses front wideband sensors that may give you an idea here http://www.subaruoutback.org/forums/66-problems-maintenance/49537-p0420-diag-3.html#post481085 .

The complete thread has a lot of good info.

The rear sensors, behind the CATs, let the computer know if the CATs are functioning proper or if there is an issue with the exiting trim in the exhaust.

If you can record and post the readings, we could see what you are looking at for a better explanation of what is occurring.
 

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Registered
2004 Outback Wagon EJ259 - 4EAT
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121 Posts
Discussion Starter #3
Ah, I appreciate the offer. Going back to the computer, I realized I was comparing one front and the rear, not the two fronts like I thought. My apologies.

On the other hand, the stumbling idle that i've been having seems to have been cured by a good throttle body cleaning, and probably isn't O2 sensor related like I imagined.

The thread you linked was indeed very informative, thanks for posting it.
 
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