HOW did your truck (simonsocm) get lucky enough to have that 2 fuse ECM power holder junction block intstalled on the firewall? EVERY Detroit powered truck I've ever seen or owned, all being pre-egr Series 60 powered trucks (Freightliner, Kenworth, Int'l, Peterbilt or Volvo ) has always had those two fuses down somewhere in the area of the battery box, if not inside the battery box. I'd MUCH perfer having them up on the firewall where they'd be much better protected from weather, road debris, etc.. As a side note: at least in my truck (1999 379) there is a third 10-amp fuse on a 5 circuit strip behind the tach/speedo dash panel. When it blows, not if, that will make the engine also NOT start. WHY, idk. It's tied into the ECM power/starting circuit somehow.
Mine is the same way, have a 10 amp fuse right behind my tach as well, does the exact same thing, no idea how it's all tied in. I think because my truck was originally a Canadian truck maybe plays a part of it as far as where the main ecu fuses are on the firewall.