Mx13 head scratcher

[Perro903]

2016 t680.mx13

New customer asked if I could look at truck, sure why not. Pulled up, hooked up and retrieverd code. Many random codes. I clear codes and some of the previous come up and then some new ones. Every time I clear code new codes come up and some of the old ones go away then come back up later. The craziest part is there is no CEL only calling for a Regen. The egr has been blocked off but I do not know if it's "tuned" for it. I do not know the history of this truck. When I checked voltages and resistance on wires, from ecm and out of ecm, to the first sensors I got codes for (egr temp, temp after bpv, oil temp, and humidity) they checked out fine. After clearing couple of times those went away just to get a new set of sensor faults (coolant level, coolant temp, oil pressure, can communication on bpv, scr temps). Did nothing but reset fault. Maybe the ecm go bad?