So I just replaced my own 0xygen sensor and wanted to put my input on here to hopefully help out other owners in my situation.
I own a 2005 Lexus IS300 and the engine light came on. Went to Autozone and for free had it diagnosed as my Bank 2 Sensor 2. They had Bosche and Denso for $95, so instead I just borrowed their oxygen sensor socket.
I purchased Denso (great reviews) from Amazon for $52 with shipping. (Part # for B2S2 is 234-4517 Oxygen Sensor)
The B2S2 sensor screws in from under your car by the T-pipe.
Make sure to spray plenty of lube 1 day before to make it easier to unscrew since there will be rust. The other end of the harness will go from under the plastic cover to inside your car from under the passenger seat rug. In the picture description, I called it a "cargo" but i meant plastic cover, sorry.
Unplug your negative terminal from battery and remove your front passenger seat. Some say just move it all the way forward which I did, but was way easier to just take seat out since you will need to be passing the o2 wires under the rug
I jacked up my car and couldn't unscrew the o2 sensor since it was so rusted and not much leverage from laying under car so I went to local oil change/smog shop and paid $10 for them to loosen it for me.
Unscrew the o2 sensor from under the car with the special socket and follow the wires from under the plastic cover leading into your car. Unplug the harness from the old one.
You will be leading the other end of the o2 sensor, which is the harness from the outside to the inside. Plug in both ends of the harness and you are done.
Denso o2 threads do not require anti-seize since they come pretreated with it already and you do not need to splice wires since other end is a simple harness. Saves you the trouble
I forgot to point out that the bottom picture is where the harness end of the o2 sensor comes in from. This is located pretty much center to end of where your passenger seat will be. After you pull the harness end from that opening, then you will plug in harness to the other harness inside your car, which will be located under the rug approximately on the front end of the passenger seat as shown from above pics. Sorry if its not organized properly, I need to shower and eat but wanted to try and help