Dies in middle of Highway

Driving for a half hour going up grade before. Elk
viewing area on 38 motor shut and still have lights
first thing I do is switch tanks and knowing both
are full. I pull over at weight station chech all fuses
and relay panel under hood .Of course why would i
check for fuel pumps under the hood they are in
tanks right .Also check ECM and a tiny box on
driver fender actual unplug that and put back in
.Could be as simple as a Coil or do both fuel
pumps go out at same time? The motor has
150,000 for 4.9 6cylinder