With the premise that I have no direct experience with either of these two codes, one thing I noticed in my 35d at one point is that the NOx module is right below the drain for the AC condenser.

In addition to that it is also in contact with an insulating mat placed on the transmission cover. Said mat get soaked up with the condensation dripping (what is circled in red is the A/C drain).



When I inspected my module was showing some superficial corrosion which I went ahead and cleaned off.

Like you mention in your post, it wouldn't be the first time someone has a NOx code where the culprit is actually the NOx module, not the sensor itself.

My theory (just a theory, nothing more), is that condensation eventually makes it into the module and fries it (I also went as far as saying that the failure in the driveshaft is the result of the same combined likely with low quality bearings on the u-joints...). There was also some superficial corrosion on the transmission cross member.

In any case, I rerouted the A/C drain, removed the mat and drilled holes in the plastic cover so condensation doesn't puddle.



This may not be much help and may actually be totally irrelevant, but if in your quest you end up finding the culprit in the NOx module, I'd love to hear that and would love to see the condition of the module itself.

I wish I could help more...

__________________