Lambda tool - oxygen sensor socket

From Knowledgebase

The lambda tool is a special socket designed for removing, and especially installing, oxygen sensors.

It features a slot down one side so the wire to the sensor has a place to go when the socket is in place.

For removal, if replacing the sensor, this does not matter much, and it might be easier to cut the wires off and use a normal socket for more torque to break the old rusty threads loose. Note that once you cut those wires, your car won't run well until you put the new sensor in!

For installing, it is a must (unless you want to use a wrench), since the wires get in the way of a normal socket.