Oxygen sensor

2004 Tacoma 4 door V6
Harness routes under passenger seat.
The sensor has a shield and so far I have not been able to loosen
the nuts because of very small space.
Should I drop the tail pipe or what tools work?

Plus I replaced the AF sensor and broke the lock tab.
Plan on a plastic tie for male and female harness,then a
third tie to secure them together.

 

Soak them in acetone and transmission fluid 50/50 mix and let it sit. Use a 6 point socket.

 

Check out this thread, seems like you are after?

https://www.tacomaworld.com/threads/rear-o2-sensor-done.142451/

 

I finally did what you did,took a grinder to the shield.
Do I need another shield?