So since today was 57 F (14 deg C) I decided to change my O2 sensor I picked up yesterday. I ordered it from Subaru Genuine parts dot com. Cheaper than buying it here in Canada.
I disconnected the battery, then I removed the back part of the air filter box and the passenger side wheel to have better access to the O2 sensor wire.
I then unplugged the O2 sensor wire. Red below
Here is a view of the O2 sensor from the passenger side wheel well. Red O2 Sensor, Green tie down. ****Ensure you put the wire back into this tie down. Its to prevent the wire from being wrapped around the driveshaft****
I tried using a O2 sensor socket, but couldn't really get it in due to being so close to the engine subframe.
So I used a 22 mm flare nut wrench from the engine bay. I couldn't really get to the sensor from underneath. I was able to turn the wrench behind the drive axle thanks to the slight bend in the wrench. Afterwards it was easy to remove by unscrewing it by hand. I was also twisting the wire counterclockwise while turning the O2 sensor to prevent the wire from binding.
This is what it looked like
I then reconnected the battery and started it up and let it warm up to operating temperature.
It took me about 1/2 hour to replace the sensor. Was fairly easy to do. As usual, more tech stuff to be posted in the future!!!!