Oxygen Sensor
 

I am new to this forum -- usually on the 911 forum, but I also have a 1994 BMW 525 i, with 162,000 miles and it has recently about driven me to the poorhouse. I've always been intimidated about working on this car much myself, but I think I am going to have start.

My check engine light came on today and, based on my mechanic's diagnosis the last time it was in, it is probably the O2 sensor. On a scale of 1 to 10 how hard is the repair and where is the sensor? What's got to be moved or removed to get to it? I'll order from our host and do it myself, if possible.

Thanks.

Hello,

I am disapointed that a response was not posted after so long. I have not been on line looking for stuff for a while and came across it.
Hopefully you had the answer from someone that it is easy. The difficulty is making sure you order the right one! Out of the two I could have ordered, wouldn't you know I ordered the wrong one. Make sure you call the order desk with the vin #.
The replacement goes easy. Disconnet the negative terminal. Jack up and block the vehicle so you can get under it. The sensors are on the exhaust towards the mid section of the vehicle. Disconnect the connection at the connector and loosen and remove the sensor from the exhaust. Install the new ones and keep them clean. do not touch the probe end of the sensor. I have heard of some problems with the removal. I had none. just the right (tight wrench) tool and it comes off. be careful to not rack your knuckles. Make sure the tail of the cable is restrained from dragging or interfering with the driveshaft.

Rich

Thanks for your reply. I have been out of town and today am getting a crack at it. I have located both ends of the sensor, but cannot figure out how to get to the end up in the exhaust. I cannot get a wrench, channel lock, or anything else on it. What is the trick?

Thanks.

I too am usually on another part of this board and was amazed to find this question on here. I have a 95 540I also and am needing to change the O2 sensors. They are the original ones that came with the car and it now has 113k on it. I was wondering how to change them myself as the mechanic wanted around 500 to change them both. I saw a special tool they sell to replace them for about 15.00 and I think I am going to just buy it with the new sensors. Any advice would be appreciated.

Right. I found the tool at a local parts store for about $12.00. All it is is a socket with a slot up the side for the cord. Actually, with that socket, getting the sensor out is a breeze. The hard part is threading the new one back in as you are working blind laying under the middle of the car. Be patient and careful because you want to protect the threads, but once it is on tightening with that socket is also a breeze.

Good luck.

One thing to keep in mind. Just because you change the sensor, does not mean that the check light will go off. It will need to be reset. I'm not sure how it is on the 5 series but on 3 series cars, there is a box connected to the speedometer cable. This box measures miles & every 25,000 the oxygen sensor light will go on. To reset on the 3 series, there is a button on this box and it simply needs to get pushed.

Vern