[Kcolg]

Check engine light is on and error code says it is the Upflow O2 sensor. Where is that exactly? and where is a good/cheap place to buy a replacement?

 

[Creech]

find the exhaust manifold. Should be right around there probably in the downpipe from the manifold.

check Auto Zone, Advance Auto or Pep Boys. They have universal 4-wire O2 sensors for about $60. Wouldn't recommend those because I don't believe they give as accurate a reading as the factory replacements taht are about twice as expensive, but they'll work.

 

[Mrfreeze5]

I had to use one of those universal sensors when I replaced catalytic converter O2 sensor. I went to 3 Autozones, and an Advance Auto looking ofr the right sensor. What they had listed in the computer for my ZJ had the wrong harness on it. We looked at ones for other model years and even cherokees and didnt find one that matched the harness on the one I took off as well as the element that goes into the pipe. I had to use the universal and reuse my old harness and it seems to work fine now. Get the exact part number if you can but check it to make sure its the right one first.