This describes the removal and installation of the rear O2 sensor behind the catalytic converter for 95-99(Federal Emissions) Maxima/I30s.
PB Blaster (or other rust penetrant)
Flat Head Screwdriver
Jack and Stands
First you will need to remove the bad O2 sensor. Use generous amounts (frequently) of the rust penetrant on the sensor where it goes into the exhaust pipe (bung).
While allowing the the penetrant to work, follow the wire from the back of the sensor to where it goes into the floor panel. Use a screw driver to pry the large rubber grommet from the floor pan. Once the grommet is loose, disconnect the plug that attaches the sensor to the harness.
Now use the 22mm wrench to remove the bad sensor from the bung. Continue using the penetrant as needed. This is the hardest part of the process (especially if you live in a snow state).
This is what you should be looking at once the bad sensor is removed.
Screw the new sensor into the bung and measure where the grommet will be positioned. Mark this position with a piece of electrical tape, and remove the new sensor from the bung.
Wrap the electrical tape around the wire cover on both sides of where it passes through the grommet. I added tape where the wire come out of the rear of the sensor.
Apply the anti-seize that comes with the new sensor to the threads; use plenty and coat all the threads, you’ll be glad if you have to do this again. Screw the new sensor into the bung and tighten with the wrench.
Attach the sensor clip to the harness.
Push the grommet back into the floor panel until you feel/hear the plastic backing catch, and the grommet is secured.