What to do?!!! Cummins engine keeps shutting off!

Hi everyone, I have a 2008 KW T800 with a cummins isx500 engine 500hp used for heavy haul. The truck was running great but a few days ago it shut off while running. We noticed that when the temperature reached 200 on the gauge it shut off before the fan clutch kicked in. We checked the wiring for the fan clutch and everything seems fine. We connected the computer and it gave an active code for the After treatment doser. Replaced it with a new one, turned on fine but when it reached a temperature of 200 it shut off again before the fan turned on. I was told that the engine is protecting itself which is why its shutting off and that's fine and dandy but why is it shutting off? Has anyone had this problem? What could it be? Any help appreciated. Thanks!

 

Yeah seems to be working fine.

 

It's supposed to turn on by itself at a temperature of 210 and it wont even reach to that point.

 

Would've the computer have picked that up when it was connected?

 

When the engine is running and the temp starts to increase as soon as it reaches 200 it begins to shut off. The fan is supposed to turn when it reaches 210 but before it even gets there the engine shuts off. The guys at rush hooked up the computer and it said it was the doser so I purchased a new one and replaced it but that didnt work. I didnt want rush to replace it cause they are pricey so I hired another mechanic to do it thinking that would be it but apparently its not. So when the engine cools down it'll turn on again but once it starts to heat up same problem occurs.

 

Just had another technician hook up the computer for a diagnosis now its saying "ECU power output supply voltage #1. Data erratic, intermittent or incorrect." So now it's the computer? Going crazy!