I'm going to, after reading the thread, redefine (if needed) that the dealer probably called you to say the NOx sensor failed….that was likely interpeted as the 'Knock Sensor' failed……and reported as such.
As a tired old wrench, we call the component (phonetically) a 'Knocks' sensor……as opposed to a Nitrogen Oxide (NOx) content sensor.
I guess this can easily be confused with a 'Knock Sensor' which is a vibration reading component found in gasoline engines.
Kinda funny to read though.
Rob