Keeps blowing the ignition fuses, why?

I I have the vehicle listed above 3500 cutaway van. The ignition fuses keep blowing can off powertrain transmission. Module fuse blows once put in fuse box sometimes don’t blow until car is cranked this thing down all power to the powertrain which is the transmission send it into limp mode, once this happens transmission is stuck in second gear I don’t know where to look at for short to ground if possible is number fuse number six in the fuse box, ignition fuse, which controls, PCM,ECM.