I have a CEL light and had the code read. It came up with a P0140 and P0141. It seems that the passenger (bank 1) rear (downstream Sensor 2) is malfunctioning, I have 77k miles.
Does anyone know how to get ot this o2 sensor? Can I reach it from the engine bay or do i need to remove the bottom covers / wheel?

 

Look under the hood, then under the car.

 

I replaced the rear O2 sensor after getting Bank 1 Sensor 2 Code (P1040).

So I changed the rear, passenger side O2 sensor. Attached are a few photos. It can be done entirely under the hood. I purchased Walker 350-341085 Sensor for $100 from carparts.com.
(https://www.carparts.com/oxygen-sens...s/wkp350341085)
Steps
1. Take off engine cover and stabilizer bar
2. Remove the aluminum shield. You will need a 10mm wrench or socket. There are 4 bolts to remove
3. You will then see 2 O2 sensors and catalytic converter.
4. If the sensor is tight get a 22mm socket. Otherwise use an adjustable wrench (it worked for me).
5. Unclip the sensor "wire" from 4 or 5 clips. You need to pry them open (almost like a dovetail connector)
6. Install the new sensor. Add a little anti-seize compound to the threads (do not touch the sensor). Connect connector to female end.
7. Replace everything back
8. CEL light should go away after 20 - 50 miles.


Aluminum cover is off. Remove the O2 sensor closest to the heatshield

Remove the aluminum heat shield to expose the cat and O2 sensors.

 

Well done!

 

What year is your car?
US cars have 8 year warranty on emissions components.