Do you have scanner that can plot a graph of your O2 outputs?

If not, get one. You can use a $20 WiFi obd adapter and $10 app like obd fusion.

On both of my 2001 X5 when the cats got tired I was able to reset the clock with some defoulers. It will take a tired cat and get it just over the threshold of acceptable but I need to see the graph of the sensor outputs to get a better idea.

The first ones were like $9@ but I couldn't find a good deal like that on the second set which were $30@ but far better design two piece 90° so not only 10x easier to install now it's 10x easier to get to the o2 sensors to change them as well (which I needed to as one failed with just over 2 years use)

The defouler only smooths out the signal so the cat can't be completely gone and still must function.

Crucially; if you are close to needing an emission pass, there is something you can do as well that is not snake oil like you reverse m referred to as found on the internet

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)