[AndyW]

Most DIYs for the rears seem to indicate it is "straightforward". Even the Bentley manual direction is simple (but it does use the BMW special tools). This PSA is that, if you have c-PE downpipes, it is not. The angles are such that you really need to remove the rear DP to do it. As it was, I needed to disconnect the exhaust pipes, crush the heat shield a bit above the sensor (to fit the socket) and temporarily remove the tie wrap from the new O2 sensors so the socket and wrench 22mm tools could fit around the wires. I also removed the heat shield and sensor wire bracket from the transmission. In hindsight, I should have just bit the bullet and removed the rear DP. Took me over 4 hours to figure out, by trial and error, that an engineering sadist had perfectly positioned them to be a PITA, and then figure out and execute the job.

HTH someone avoid the swearing and the bashed knuckles I experienced doing a "simple" job.

[blaster3500]

What o2 socket were you using? On my e90 with CPE downpipes I have easily changed rear o2's using a short o2 socket.

[nissubaru]

I forget which dps I have on my car but to get both O2 sensors out I have to drop one of them. I wanna say it's the front downpipe, whichever is closest to the center of the car.

Just did this a couple weeks ago when I did my clutch replacement, I had already dropped the exhaust so it was just the front O2 sensor and the v-band clamp that I had to remove. Didn't see any other way around it, maybe with a crow/O2 socket but I use a 7/8" hand wrench with the bottom sawed off lol

[mweisdorfer]

Originally Posted by AndyW

Most DIYs for the rears seem to indicate it is "straightforward". Even the Bentley manual direction is simple (but it does use the BMW special tools). This PSA is that, if you have c-PE downpipes, it is not. The angles are such that you really need to remove the rear DP to do it. As it was, I needed to disconnect the exhaust pipes, crush the heat shield a bit above the sensor (to fit the socket) and temporarily remove the tie wrap from the new O2 sensors so the socket and wrench 22mm tools could fit around the wires. I also removed the heat shield and sensor wire bracket from the transmission. In hindsight, I should have just bit the bullet and removed the rear DP. Took me over 4 hours to figure out, by trial and error, that an engineering sadist had perfectly positioned them to be a PITA, and then figure out and execute the job.

HTH someone avoid the swearing and the bashed knuckles I experienced doing a "simple" job.

You should of just taken the downpipes out. 🧐

[AndyW]

Originally Posted by blaster3500

What o2 socket were you using? On my e90 with CPE downpipes I have easily changed rear o2's using a short o2 socket.

I ended up using a long O2 socket and holding my mouth right to get the socket wrench in there. The short one i had was the traditional type and with the tab was too wide. The schwaben-type tool worked for the inboard one but not the outboard. The most difficult part was actually trying to get leverage to get it started in to the hole...lol.