The 12v on b and c is from the ecm. There is what is called a pull up resister in the ecm. This is ok.
ecm/sol fuse powers the purple wire to the trans at a. This is fed through the brake switch. 12v brake off, ov brake on.
Ecm/sol fuse also powers wastegate and can purge solenoids, egr relay and ac cutout relay.
Does the fuse blow immediately? Maybe unplug all those things, then plug them in one by one until the fuse blows?