Engine shuts down going down road
 

I have a 99 379 peterbilt with c15 cat motor, it has shut off 3 time going down the road as if I shut key off, this truck does not have wire coming from battery to ecm , assuming it's comes from starter and this truck also has engine cutoff timer button that I push to shut off truck when I turn key off. We have replaced ign switch, replace 75 am Relay behind pryometer gauge panel. As of typing this I haven't had truck back on road yet to see if it has solved a thing due to cold temps but will be going back out Sunday nite. So I'm asking for any advice e or maybe what I can try or look for any other areas, thanks in advance

I had the exact same issue in a 2000 peterbilt. 550 Cat. Driving down the road, engine would just die (several times before I got irritated enough to get it into a shop). They put it in a Pete house in Lubbock and had to add gold pins to the ecm pins. It may not help at all, but that was the cure back then. I would assume that the wiring harnesses and plugs would be almost identical to whatever it is that your running.