The same thing happened to me after adding the Berryman Chemtool ( which is much harsher then techron).
Techron is usually quite safe.
It could be related or unrelated.
If related it might go away by itself.
I would do some more driving before I worry about replacing sensors.
Clear it and do some driving.
if it comes back clear it again..
Only if it still comes back after a couple weeks of this would I consider replacing sensors.
I waited for 1500 miles (probably too long)
It was the sensor not the cat in my case.
A broadly similar problem we ran down here on ThePath
http://www.thenissanpath.com/viewtopic. ... 1606344939