redfishtd

As you can see on an o5 5.4 fuse102 does feed the start relay but you pulled it and it still blew. Most of the time its the transmission switch wiring underneath truck but then there is the ignition switch/wiring inside steering tube . Putting oversize fuses in it very bad you can burn the wires badly melting the insulation all along the way . You are making a heater out of that small wire . Outlet's in a house are 14/12 gauge and they are fused 15amp -truck wires are much smaller .Therefore they get hotter faster.
I would be looking all along the wiring harness for chafing /rubbing . If you don't see anything replace that trans switch . There are some tricks you can use if all else fails . You could put a small 10 amp fuse ahead of trans switch to see if it blows to eliminate ignition switch wiring but put it inside where it starts going towards floorboards .
make sure somebody has not added something to this run like aftermarket remote start -they are horrible .

needsmoarturbo

? Fuse 101 goes to the starter relay. Fuse 102 goes to the ignition switch unless you mean how it does work it's way through the ignition switch to the neutral safety switch and over to the trigger wire of the start relay when in the start position?
It is good advise not to put a higher amperage fuse in a place where lower is specified, unless you want wires to melt or possibly start a fire.

redfishtd

f101feeds the contacts of starter relay ,f102 feeds coil of starter relay . he is blowing 102 which covers interlock of transmission switch and wiring of steering column going to start switch . I'm only interested in getting the exact area of his failure isolated. Trans sw under driver seat or steering column. Or a remote start package .

redfishtd

A remote start package would have to use the same safety interlocks of trans sw and only try it in neutral or park . It would bypass keyswitch . Only way to find it is by searching manually for extra wires/going to a extra module. .