2017 Cascadia dd15, nox sensor issue

hey everybody,
got a 2017 cascadia with a code spn 3216 fmi 13 for a nox sensor before the scr catalyst signal not available. checked chassis wiring, have 12.4 volts on pins 1 and 4 and 63 ohms of resistance on pins 2 and 3 so everything checks out per the troubleshooting, replaced the nox sensor and code clears and comes back within seconds, the nox sensor fault counter reads 0 but the code has 19 counts, started to doubt whether I had changed the right sensor but its the first nox sensor downstream, theres two other things that look like nox sensor towards the end but ones a soot sensor and one im assuming the outlet nox sensor, removed the outlet one and got a code for nox sensor 'behind' the scr no signal, isnt that the same thing? before and behind? but upon reconnecting it goes away and connecting and reconnecting the inlet has no change, even tried a different sensor but same thing, never seen this kind of system havent worked on a 2017 before seems weird with the ACM mounted on the box, any thoughts or ideas?

 

Took a look at these, thanks for the info, inspected the connectors and found no corrosion or any other issues, went thru the full troubleshooting and have perfect voltage and resistance, checked continuity from ACM to inlet NOx sensor and it’s all good, ran scr efficiency procedure and code still is active, don’t know what else at this point, tried different NOx sensors also, during the efficiency test inlet NOx is stuck at 500ppm while outlet changes as it should