2001 Screw, 5.4, AT, 4X4,
would not start the conventional way
battery checks out good, starter solenoid is good
fuse #21 is blown
replace fuse start with ignition key and fuse #21 blows
checked all pin connections in ignition switch, ok
each time in start position fuse blows
with new fuse in neutral still blows fuse will not start
fuse #20 is good
it has to be grounding out, is it the key cylinder?
how do I check
I can start by jumpering across the starter solenoid with key in run

 

problem solved, it was a melted wiring harness going from the firewall to the tranny
all works fine now