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HaqDeluxe 02-13-2005 02:58 PM

Substitute Bosch o2 sensors for OEM Siemens
Recently had my CATs replaced under warranty with surprisingly little grief from the dealer. I had not failed emissions but there was a noticeable rattle from inside them. 80K is the cut-off and I rolled it into the dealer at 79,800.
Anyway, since the change, and since they didn't change the O2 sensors after the CATs and since they have never been changed.... Let's change them!

Now for the question. I find the Bosch 13981 listed as an OE replacement (I double checked this on the Bosch US site) for the after-CAT OEM siemens unit but it is not exactly clear that this is correct. I have read threads that seem to state that the rich signal between these two sensors is reversed.

For a 99 S52, (Mine is in a Z3M but the M3 is the same) has anyone substituted the factory siemens O2 sensor with the Bosch (13884 or 13981) sensor?


vm 02-15-2005 05:07 PM

I didn't know that Siemens made O2 sensors and couldnt find them on Siemens website. I have always assumed that they were Bosch. Not directly related to your question but just to tell you that the only function of the after cat sensors is checking on the status of the Cats and nothing else. They will not help with mixture, fuel economy, etc. so it might be a waste of money to try to change them before they are broken or before the 100k service date.

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