Locating O2 sensors

2004 NISSAN XTERRA
214,000 MILES • 3.3L • V6 • 4WD • AUTOMATIC
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LISA D CAREY
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O2 sensors on the driver and passenger sides has come up as an error code. I am trying to figure out if it is the upstream and/or downstream. It is the top that has been identified.
Sep 30, 2017 at 10:53 AM
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STEVE W.
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First, what is/are the actual codes you have. There are many times an O2 sensor has been changed when it was not the real problem.

As for how many sensors you have, four total. Two in front of the forward converters and two behind them.
Bank one is the passenger side. Upstream = Sensor 1 / Downstream = Sensor 2.

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Sep 30, 2017 at 11:41 AM