That darn sensor (64116917001) has such a limited life span, I must have replaced it 5 times by now. :-)

So, I am contemplating replacing it yet again... And started to wonder about how it actually works. Does anyone know?

For example, what allows it to detect a bad smell? And what is its electrical signal/output when there is no bad smell vs when there is a bad smell?

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2001 BMW X5 3.0i, Automatic, Gasoline