I have a Ford Fusion. I am looking at the sensor on top of the exhaust with a collar, and I cannot see how to undo it. I put the image in to show what I'm dealing with.
I don't see a way to fit a socket onto it.
How do I remove this lambda sensor?
In addition to Bob's sock puppet's O2 socket and crow's foot suggestion, I'd like to add that O2 sensors are usually size 22 mm.
In a pinch, a 22 mm spanner/wrench with enough leverage will also do the job. It helps to soak the threads in rust solvent prior to removal.