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2004 Nissan Xterra, 4x4 S/C
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Discussion Starter · #1 ·
Any advice on how to remove the downstream driver's side oxygen sensor? Super awkward to get to it. Tried to use one of those tall O2 sockets, but can't get any leverage on it at all. Disconnected the sensor wire and ran it down to the sensor so I could try to get a 22mm line wrench on it, but the hex threads are literally just off enough that I can't seat the line wrench - either hitting the drive shaft of the downsteam cat... ugh!

I was gonna disconnect the drive shaft tomorrow, but it seems a bit excessive for literally removing an o2 sensor!!
 

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2004 Nissan Xterra, 4x4 S/C
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326 Posts
Discussion Starter · #2 ·
Ok, so I gave up trying to remove the O2 sensors and just pulled the cats, seeing as those needed to be replaced anyway. For anyone trying to remove the cats, you can get to all 3 stud nuts on the right (passenger) rear catalytic converter using extensions. 2 of the nuts are easy and can be reached with a direct extension, the 3rd one required a bit of creativity...



That's a looong extension + swivel-head + socket to get at it. Heating these with a torch first + penetrating oil + using a socket is the best way to ensure you don't snap off the studs, which turns into a different headache -> especially if you aren't pulling/touching the front cats.

As for the left-rear (driver side) catalytic converter, 2 of the stud nuts can also be reached with an extension, but the top stud is directly behind the downstream O2 sensor -> so you have to be able to remove it before you can unbolt the cat... ugh. Still trying to figure that out, stay tuned.
 

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2004 Nissan Xterra, 4x4 S/C
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Discussion Starter · #3 ·
UPDATE: Oh man, what a pain. Finally got the drive-side rear o2 sensor out. Trying to use an O2 socket didn't work, started blowing out and stripping the sensor nut so had to rethink my strategy.

Ended up disconnecting the sensor wire, then removing the wires from the sensor plug using a weatherpak connector tool so that I could get a closed box-end of a 22mm wrench over the wire. Was able to just fit it on the sensor from underneath the truck, then did the 2 wrench bigger-lever trick. After some hitting it with a hammer to 'vibrate' the rust-lock and then some sweating it finally popped. Brutal.











I even considered removing the catalytic converter first and then wrestling with the sensor once it's off the truck, but you can't even do that b/c the sensor blocks access to one of the studs/nuts which attach the downstream cat to the upstream cat...
 

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2004 Nissan Xterra, 4x4 S/C
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326 Posts
Discussion Starter · #5 ·
Love the double wrench method!
A butane torch works wonders to free up seized metal. Not sure if you tried that or if it was an option.
I was trying to save the O2 sensor, I think heating it is usually only a viable option if you're replacing - otherwise the heat cooks the internals? At least I remember hearing that somewhere before. But yes, heat is the best - in this case I resorted to heat but it still wouldn't budge!
 
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