O2 Sensors

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O2 Sensors

Post by forum-guru » Sat Dec 09, 2017 1:55 am

Since this question pops up from time-to-time, here's an easy to follow diagram that illustrates what they mean when your OBDII code scanner (or manual) tells you something like "O2 sensor, Bank 1, Sensor 2":
Oxygen 02 Sensor FAQ and Info.jpg

What does upstream and downstream mean?

Simple, upstream means the O2 sensor is "upstream" of the catalytic convertors, meaning before the catalytic convertors. Downstream means the O2 sensor is "downstream" of the catalytic convertors, meaning after the catalytic convertors.


What brand of O2 sensors should I use for replacements?

Pay close attention to this one so you can do it once and do it right! The Jeep Wrangler TJ is extremely sensitive to all oxygen sensors other than NGK / NTK. Bosch O2 sensors and all the others (including the crappy Chinese brands you'll buy at your local auto part store) are very well documented as not working properly with our TJs. In other words, you plug them in and you assume all is well, until you notice your check engine light isn't going away. This is almost always due to the fact that you didn't use an NGK / NTK replacement O2 sensor.

I'm going to break down which sensors you need based off what year your TJ is. The part numbers (and information) below were taken directly from the NGK website, so you can assure it is 100% accurate (even double checked each individual year and model before writing this thread).


4 Cylinder Engines

1997-2000
NGK #23506 - Bank 1, Sensor 1 (Upstream)
NGK #23099 - Bank 1, Sensor 2 (Downstream)

2001-2004
NGK #23138 - Bank 1, Sensor 1 (Upstream)
NGK #23141 - Bank 1, Sensor 2 (Downstream)

2005-2006
NGK #23159 - Bank 1, Sensor 1 (Upstream)
NGK #23159 - Bank 1, Sensor 2 (Downstream)


6 Cylinder Engines

1997-1998
NGK #23151 - Bank 1, Sensor 1 (Upstream)
NGK #23099 - Bank 2, Sensor 2 (Downstream)

2000
NGK #23122 - Bank 1, Sensor 1 (Upstream)
NGK #23506 - Bank 2, Sensor 1 (Upstream)
NGK #23099 - Bank 1, Sensor 2 (Downstream)
NGK #23099 - Bank 2, Sensor 2 (Downstream)

2001-2003
NGK #23139 - Bank 1, Sensor 1 (Upstream)
NGK #23138 - Bank 2, Sensor 1 (Upstream)
NGK #23142 - Bank 1, Sensor 2 (Downstream)
NGK #23141 - Bank 2, Sensor 2 (Downstream)

2004
NGK #23137 - Bank 1, Sensor 1 (Upstream)
NGK #23135 - Bank 2, Sensor 1 (Upstream)
NGK #23132 - Bank 1, Sensor 2 (Downstream)
NGK #23531 - Bank 2, Sensor 2 (Downstream)

2005-2006
NGK #23018 - Bank 1, Sensor 1 (Upstream)
NGK #23160 - Bank 2, Sensor 1 (Upstream)
NGK #23159 - Bank 1, Sensor 2 (Downstream)
NGK #23158 - Bank 2, Sensor 2 (Downstream)


Misc Installation Notes

When installing new O2 sensors, be certain to use some anti-seize on the threads of the new O2 sensors! This is important, and will save you a huge headache should you ever need to remove them in the future.

In addition, a O2 sensor socket will greatly aide in the installation and removal of O2 sensors.
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