My sensor seems to have been in quite a while, how would I best go about in loosening it up? Besides that, there seems no way to get a wrench around the hex-shaped part of the sensor. Does one usually use pliers instead?

 

My sensor is the type stuck in the first catalytic converter.

can you get a wrench in there? that's what i always use. dropping the exhaust may give you more room to work with.

 

you could use a torch around the catalytic converter if you've done that before and know how to do it. torch the threaded area around the O2 sensor but not the sensor itself. then try to break it loose.

 

or spray the O2 sensor down with liquid wrench a couple days in a row.

I would invest in a o2 sensor socket, they are 1/2in drive and work like a breeze. I used to fight with them but now all I will use is a o2 sensor socket. It also gives you an excuse to add another tool to your collection!

 

Scott

O2 sensor socket i bought does not work on my AWD XT6, not nearly enough room between the sensor and front diff. vehicle dependent.

I remove O2 sensors all day (being in the exhaust bizz). I have strong faith in the 02socket system. If ever you cant get a box end on there, pop on the handy 02 socket, grab your wratchet and your good to go. Works like a champ on my 96 imprez, which problibly has the same setup as what your talking about.

The socket I got looked like it meant business, but sadly the clearance between the cat and the differential is too narrow to fit the socket, even less the socket and wrench assembly. :-(

 

http://www.ultimatesubaru.org/photos/showphoto.php?photo=3909&size=big&sort=1&cat=500

 

This shows what i'm talking about. I've also now disconnected the sensor and my car doesnt seem to give a damn. No CEL, nothing. Not that I always want to be running around with an ultra-rich fuel mix...

the socket has a hex on the top so if a ratchet doesnt work, you can fit either its a 1" oe 13/16" open or box wrench