I've got a 2005 Hyundai Sonata. Its check engine light came on and the code reader from Advance Auto said "Passenger side bank" or some crap...

Anyway, I got the replacement sensor but... what's the correct tool to get this stupid thing out of the damned exhaust down pipe?

Have you tried a 22mm or 7/8" wrench?  

If that doesn't do it, you'll need something like this or this.

For one-time use, a cheap one from Auto Zone will do.  They might even offer a free rental.

dont forget to spray liquid wrench on the threads first and let it sit prior to attempting to remove the 02 sensor.

Just be ready for it to slip and make you drive your knuckles into something sharp. The last one I bought from Auto Zone opened up as soon as I put the wrench to it. YMMV.

Really, you can use just about anything to remove the old one since you're not going to reuse it. You can even snip the wires off of it and use a standard deep-well socket. You'll only need the specialty tools to put the new one back in.

Looks like a deep-well socket with a "u-shaped" cut out.  The cutout gives a place for the wires to exit.

You can buy one at Advance Auto or a Pep Boys for around $5-$7.

Please put some anti-sieze compound on the threads of the new O2 sensor before installing it.  This will make life much easier if you ever need to relace it again.

Thanks for the replies. The Denso sensor I got from Advance Auto didn't come with anti-seize. I wasn't going to use it but, since y'all are so convincing I'll get some.

I figured it was something like 22mm and I was right. There's not a lot of space to get anything onto it to get it out. Dammit. I'll need a can of PB Blaster too.

I wasn't planning on cutting the wires to get it off, I don't like doing that. I just need to find a 22mm crow's foot. I think I've got one and would rather NOT have to buy or borrow one. It's on my list of things to accomplish this weekend.

That, and check the serpentine belt on my Maxima... it's got some miles on it and probably needs to be replaced... the check engine light has been on it for months too... geez... all this stuff to do.