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?

enter image description here

  • 6
    I would encourage you to make an edit to include an image of what you're talking about so we can properly assist you. May 20, 2016 at 18:22
  • The socket simply slides inside the heat shield that's around the sensor May 25, 2016 at 3:54
  • the 22mm lambda socket is to big to go in, and when I look in it, I can not see anyway that a socket can grip the sensor. I have welded a flat bar across a socket and clamp it onto the flats of the collar. I will not be replacing this kind of lambda sensor to the car. May 26, 2016 at 18:49

2 Answers 2


It should look something like the following picture. The flats for the wrench are at the bottom so you may not be able to see them depending on the location. They also might be covered by a heat shield.

enter image description here

You use something like the tools pictured below to get it off.

enter image description here

enter image description here

  • Special tools are not strictly necessary. If you are committed to replacement, knock off the wire end with an air chisel, and put a standard wrench or socket on it.
    – kmarsh
    May 25, 2016 at 2:26
  • @kmarsh In some cases they, as this application as well as others have heat shields blocking access to the wrench flats. While you method will help you get one out, you can't tighten the new one that way. May 25, 2016 at 3:56

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.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .