HELP! I'm having trouble with engine shut down!

Hey guys,

I'm new to the forum but looks like a great community. Hopefully someone here can point me in the right direction. I've look through everything I can find but can't seem to diagnose or fix this issue.

I've got a 2011 Cascadia 116. 1st thing in the morning the truck is having a check engine light come on then after a little bit a stop engine light will come on, then begin flashing then shut the truck off. This has been going on for a week or so now. All other gauges and things seem to be fine and in normal ranges. I use the override and after 30 min or so eventually the lights will go away. I've occasionally had them come back on intermittently during a trip but usually its just during the morning. I've heard possibly low coolant but I've checked it numerous times and it seems to be in the normal range.

One thing to note would be that we put a new alternator on this truck about 2 weeks ago but the voltage seem to be reading fine. I don't think it's related but wanted to make a note of it.

I've looked through diagnostic menu on the truck and it gives me to faults - both read rad 76 - one has a spn 520193, and the other a spn 520192. I've look everywhere I can and can't find a definite answer on these anywhere.

Any advice or help on this would be greatly appreciated. Thanks.