Do I need to replace O2 sensors no codes 134k miles
 

Do I need really need to replace oxygen sensors when no codes but mileage at 134k miles? Fuel mileage has been the same for years. It's about $440 for the 4 sensors from fcpeuro. Wondering if this is a worthy preventative maintenance or just hang on until they fail or throw codes. I don't think O2 sensor failure would be catastrophic.

Thoughts?

Good day!!

I may get a lot of hate mail about this thought, but I only change items that are broken or have worn out... I don't wait for a tie rod to fail before replacing it... Obviously... But an oxygen sensor is one that won't get changed unless the computer is telling me it is time... I think some items BMW recommends on replacing at certain time or mileage limits is Preventative Maintenance to keep the annoying CEL or SES light from illuminating... The other items, like LTF is them getting out of replacing fluid... I don't believe any fluid is made so well that it will last 300,000 miles...

So, my vote is replace when it gives a code or performance degrades substantially...

Cheers!!

I think you're right- I will defer to the computer the decision to replace the oxygen sensors, especially since they're expensive items.

Thanks!

If you have a scanner that allows you to view real time live data (ie Torque Pro) you can see how well the 02 sensors are working. the precat 02 sensors voltage should be jumping up and down, whereas the post cat 02 sensors should be at a constant voltage.

Yep, I have INPA, DIS, and ISTA. Thanks Upallnight for the info!

I agree completely. Definitely don't replace the downstream ones until you get a code, at least.

I wondered same as the OP when I got my '01 3.0i at around 170k miles. Maintenance records indicated they were original (and subsequent removal seemed to confirm this), and even though the truck ran great, I hoped for better MPG and was grasping for solutions.

After research, I ended up replacing the upstream ones, with absolutely no change in anything other than a lighter wallet.

I noticed that the "universal" ones (where you have to attach the connection yourself) were the same for upstream vs. downstream. So, figuring the ones I took out were just fine, I saved them in case I need them for future trouble shooting, or to solder in if a downstream one ever fails.