7 codes J1939 system down

[tree98]

2019 pete 567 X15 performance 565 hp factory stock 92,000 mi. Did an EGR tune up about 10,000 mi ago. Today out of nowhere the dash says" increased derate in 4 hours seek service to repair scr, scr system altered or fault detected" the def tank gauge went to empty and it has 7 active codes 6688,4151,3232,2771,3868,4572,4677 all are emission sensor communication problems. So apparently the J1939 network is down i guess? So I looked at what the sensors were reading with insite and the nox sensor says "reading not stable" Then I did some troubleshooting with quickserve trying to isolate which sensor is acting up. Quickserve says to check the engine harness by unplugging the 14 pin crossover connector and then measure resistance at the 3 pin data connector and resistance should be between 108-132 ohms. I did that and it's 120 ohms, ok so the engine harness must be good. Then it says to disconnect the nox sensor and again check resistance at the 3 pin and if resistance is 108-132 ohms you have a bad nox sensor. I did that and again it's 120 ohms. So according to quickserve I have a bad nox sensor, is it possible for a bad nox sensor to cause all this? Also how would unplugging a sensor and getting the same resistance tell you the sensor is bad??