Oxygen sensor socket size?

[Wiscon_Mark]

I have had a CEL in my Forester since I bought it (upstream o2 sensor) and I figued I'd fix it, so I forked over the money for the nice and pricey front oxygen sensor and finally got it in today.

I really can't get the old one out. I PB blaster'd the hell out of it and used some adjustable wrenches on it with no luck. I'd rather not drop the exhaust as it's easy access from the top, but it's kind of an odd size and my adjustable crescent wrenches don't fit very well. I went looking at oxygen sensor sockets with the gap for the wire and they all seem to come in SAE sizes. I'd estimate the size of the sensor to be either 21mm or 22mm. Does anyone have a good solution for this? I don't want to use an inexact size and round anything off.

BTW- the reason I don't want to remove the exhaust is that I don't really want to deal with it before next year - it's rather rusty and I have a feeling I will just accelerate a flange leak if I disconnect anything.

One other note - the Denso (OE manufacturer) sensor I got is supposed to be exact fit, but the plug is a bit different than the OE sensor. Has anyone run into this?

[Thomistopheles]

I believe it's 22mm. A 7/8" tool will do the job admirably, it's a whopping 22.225 millimeters. :smt023

Edited for clarity, and also because racecar

[02_Legacy]

Usually o2 sensors are 7/8 or 22mm, they are very close to the same size.

[Dead91silvia]

90% of the time, wrenches will not pull o2's out...

Most of them are all the same size BTW... I have 2 different types, but both the same size. 22mm 7/8th's...

[Wiscon_Mark]

90% of the time, wrenches will not pull o2's out...

Are you suggesting an impact gun or something else?

[02_Legacy]

I think he is stating that you usually need something that will grip the o2 sensor on all 6 sided instead of 2. He must of missed the part about you wanting to buy a socket, but I would say definitely don't use an impact, a long breaker bar is what you need.

[decke48]

90% of the time, wrenches will not pull o2's out...

Are you suggesting an impact gun or something else?
12 point. Box end wrench and a couple wacks of the hand and they usually break free for me. Or for the pita ones i use my super deep 7/8 snap-on socket. But thats for the ones that pull out threads really, even heated

[Wiscon_Mark]

I think he is stating that you usually need something that will grip the o2 sensor on all 6 sided instead of 2. He must of missed the part about you wanting to buy a socket, but I would say definitely don't use an impact, a long breaker bar is what you need.

Okay, I figured. I didn't want to use an impact anyways. Don't really feel like replacing the cats while I'm at it.

[Dead91silvia]

NO IMPACTS!

LOL.... Yeah, get a socket (6 point) and a breaker bar. As soon as they are broke, lose they spin right off. Using a 12 point will give the possibility of rounding the sensor and that will be a bad day. They do make a 12 point, but Subaru's dont need them.

The 2 styles I have...
https://sl-i.net/FORUM/images/imported/2012/10/o202-1.jpg

https://sl-i.net/FORUM/images/imported/2012/10/o201-1.jpg

[Wiscon_Mark]

The 2 styles I have...
https://sl-i.net/FORUM/images/imported/2012/10/o202-1.jpg

I just tried this one. It wouldn't fit over the OEM sensor for whatever reason. Kept catching on the top part of the sensor's barrel.


https://sl-i.net/FORUM/images/imported/2012/10/o201-1.jpg

I just exchanged the previous one for this one. Looks like it will work better.

And no, I wasn't really thinking of using an impact. I'd hate to strip the threads in the cat.

[BattleWagon]

You dont need a special tool. just unplug it and slid the closed end of the wrench down.

[L.Michael]

^ I agree.

Have always used the box end of a wrench. Why waste your money, unless your auto parts store has a lend a tool option. But, Boxed end wrench will always work.. Just may have to use a cheater bar with it for the old one..

[kimokalihi]

I've always used a 7/8 or 22mm box end wrench. But I can see how in some cases you might not have room for a wrench.

[Odycee]

I just replace O2 last week, borrowed from Autozone, box has 3 different types similar as DeadSilvia posted(2.) I sprayed with BPlaster, sat 15 mins, used the short one in picture, removed it easily. As far as 02 sensor, it either has 3 or 4 wires should work. Two of the wires for O2 sensor heater, the other 2 for ECU (forward/return lines). Three wires 02 sensor uses 1 wire to share forward/return to ECU. I replaced mine with 3 wires from original 4 wires, it works fine. Two wires for OBD1 with no heater lines available for pre-96 models.

[shredtahoe]

I have always used the biggest pair of vice grips I can find for those stinking O2 sensors. Boy are they a pain though!