On my V8 i got both upstreams swapped out through the wheel wells on either side--didn't even take the wheels off, just jacked it up so there was more room, and cranked the wheel to either side. Just used a couple of wrenches (use box end on the sensor, don't remember size), put one on the O2 sensor, then use the other linked into the end of the other to pry with as an extension. The downstreams I got to from underneath, used an O2 sensor removal tool, but once you've disconnected the wires I see no reason a normal box end wrench won't take the downstreams off too.
Definitely knock any mud/crud off around the sensor and soak them with a good penetrating oil before trying to take them off just in case they're nice and rusted in there.
I recommend a box end wrench over an O2 sensor removal tool--i used both to remove mine and the removal tool nearly rounded off one of the upstream sensors due to the angle, luckily I was able to get the sensor out with a box end wrench.

I'm new here but I have a 2004 Limited 4Runner that I would love to keep going for as long as possible. I'm also cheap as hell and have become a bit of a mechanic just through youtube videos.

I just got this error code and I'm seeing conflicting messages online about what part I need and what is the actual problem. Do I need to replace the Oxygen Sensor? Or is this a smaller circuit issue?

Any help or advice would be appreciated.

I’m new to this forum for the most part so forgive me if this is the wrong place to post about this but can’t figure any thing else out but…
07 limited v8 o2 sensor bank 2 sensor 1. Every video I find shows the o2 sensor right inside the wheel well on the bottom of the exhaust. I’m not sure but mine is on the inside of the exhaust and I can’t seem to get an o2 socket or wrench on the sensor. Any ideas as to what I might need to do?