e60rider

Just wondering how long a DIY for the precat sensor would take and what would it involve?

What will i need to remove to get them changed out (TIS/DIY procedure anyone)? (528xi 2008)

pcy

On an I6 engine, there is enough room to work from the top on the passenger side.
Buy O2 sensor wrench (like the one shown in the link below). Once you break it loose, you can use short open-end wrench to turn and remove the sensor. There will be very little room for the wrench to turn, but can be done. I have replaced both of the pre-cat O2 sensors on my '06 530i. It's obvious that you need to do this while the engine is completely cold.

3/8" Offset Oxygen Sensor Wrench

FaintReality

Hopefully it's not seized on. Tried to replace the 02 sensors on my girls car a couple weeks ago and they would not budge with a breaker bar or an impact gun. The 02 sensor wrench started to strip the bolt as the wire opening in the socket was expanding due to the force. I even soaked the thing numerous times with penetrating oil as well as heated it up.

Ended up taking it to a shop to remove :-/ Last few threads of 02 sensor were striped and he had to retap threads.

Assuming your 02 sensors come off with no issues, it's an easy job.

e60rider

Thanks for all the input, I got done and it was pretty easy and took me about 30min's, for only B1S1. The sensor broke loose pretty easily, and FOR NOW the check engine light hasnt returned (P0135 - Not back but only drove a max of 5 miles). This is just a update for anyone else trying to do this. Again thanks for the help

pcy

Glad to hear that you replaced O2 sensors without much difficulty. When I replaced mine, I was pleasantly surprised how easy they broke loose; I was expecting for a difficult job and I had cheater bar ready and I didn't need to use any other tool than the regular 3/8" ratchet and O2 sensor socket. New O2 sensors came with anti-seize compound on the threads.

FaintReality

Many manufactures don't use anti-seize and /or cross thread them during install, which creates a nightmare come time to remove. Glad to hear you guys had no issues.