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-   -   Is It Necessary To Replace Post-Cat O2 Sensors as Prev. Maint? (http://www.bimmerfest.com/forums/showthread.php?t=670565)

kgorczyn 01-16-2013 08:28 PM

Is It Necessary To Replace Post-Cat O2 Sensors as Prev. Maint?
 
I have a 2000 528i w/ 235k miles - no codes or anything. I replaced pre-cat at 100k and 200k. Post Cat are still original.

Do they affect anything other than emissions?

edjack 01-16-2013 08:38 PM

They only monitor cat performance. If you do not get any post-cat codes, relax.

ian@jewelorjalopy 01-16-2013 08:55 PM

Nope, what Ed says. They are only there to measure the cat efficiency, and will tell you when they go bad. If they don't throw a code, keep them.

professorman 01-17-2013 05:47 PM

Quote:

Originally Posted by ian@jewelorjalopy (Post 7319163)
Nope, what Ed says. They are only there to measure the cat efficiency, and will tell you when they go bad. If they don't throw a code, keep them.

How about the pre-cat oxygen sensor for me? I have 168k miles. Should I replace them 'just because', or wait for something?

ian@jewelorjalopy 01-17-2013 10:41 PM

Unless you are having issues with them, or funny idle or other symptoms, just run them.

Even if they fail, the car will still run, and you can replace them then.

When they fail they slow down, and you can start to feel a slight flutter at idle.

(FWIW - I worked on OBDII systems for one of the Big 3 for 3 years)

kgorczyn 01-18-2013 08:35 AM

Thanks - I'll let my 1/4 million mile O2 Sensors at work a while longer :)


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