make sure the fuse to the ecm is ok , on the peter built it,s in the battrey box, if the fuse is good then trace that wire out of the battery box up to the starter area , peter builts are know to rub that wire out , so i think u have a broken wire. i have worked on peterbuilt,s for 5 years and this happens often, other possibility is the ecm box. peterbuilt has a harness u plug in to , to buy pass the box, and if it starts then ur box is finished . allso check a plug in on the fire wall on the drivers side, its a 2 wire plug in with locking clip , the pins in that plug in go bad , cut the wires and hard wire it with shrink tube . hope this gets u going, Al Larson