Thanks Matt and company for the post. It was very helpful.
I was successful after about 3 hours all told including a trip to home depot for a 22mm wrench and looking up this post! and lots of cussing!
I did a few things differently.
1) I removed the two pieces of the connector first, pulling UP on the part that you don't replace after pinching the side away from the bracket. I had spent about 30 minutes trying to pull the side that attaches to the O2 sensor down, not realizing that would never work with the bracket snapped in place to the bottom half.
2) Once I had the top half off, I used a long screw driver (and some WD40) and my finger from underneath, to push down on the O2 side connector pushing it away from the rusted locked metal bracket.
3) I was using a monkey wrench and a mallet underneath the car, I just drove up on a curb to give me enough room, and I was just stripping the O2 sensor. So I ended up clipping the wire so I could get a box end wrench over it. Even with the 22mm box end hitting it with a mallet wasn't working, so I took another long box end wrench, put it over the open end of the 22, made a 2 foot long lever arm and then slowly pushed the sensor free. Gotta remember tighty righty, but when you are upside down, righty might be loosey. The 22mm from home depot was like $6.50 vs. the fancy O2 wrench from a auto parts place at about $20?
4) After resetting the Codes using my cheapy OBD2 reader, no more P0135 code! and I can get my car emissions inspected, and I didn't pay about $1,000 for the dealer to do it. I also has another code P1739, suggested the 3rd clutch pressure switch, but after looking at this: P1739 ACURA Problem in 3rd Clutch Pressure Switch Circuit
, I just filled up the transmission fluid, put maybe 1/2 a quart of honda transmission fluid in and that went away. My clue was that the VTM light would come on after a bit of driving and then sometimes go off. But eventually it stayed on. I added only about 4 ounces first, and it went out for like 2 seconds after you started the car it went back on, so that sounded to me like the fluid flew around and there wasn't enough to cover the sensor. Adding another maybe 6 ounces and that's gone too.
Happy MDXing - Mine is a 2001 - very first black MDX in the washington DC area with over 262.000 miles on it and I've done most of my own maintenance for the past 10 years. GREAT car..