[bluesmoke99]

I have a 2003 4.3 s10 a/t. i had the ecm b fuse pop one day while parking my truck and i tried to replace it and it popped immediatly it blew again i took the orange 12v wires that go directly from the ecm b fuse to ports 20 and 57 on the ecm and clipped them. It did not pop a fuse but tested perfectly i then thought it was the ecm so i went to the local salvage yard and purchased a ecm out of a identical truck and low and behold after hooking the ecm up i attempted to reconnect the 2 orange 12v wires back together and the fuse popped again and again any advice?

 

[CruisinS10]

That fuse is hot at all times, does it only blow once you turn the key on?
ECM B also powers the Fuel pump relay and therefore fuel pump.
Did you check resistance in the orange wires from the PCM to the Fuse box?

 

[Rebel n Dirt]

1. Get a set of schematics
2. Read said set of schematics.
3. Test effected circuit with a DMM and find the actual problem.
4. Fix actual problem instead of assuming and throwing parts at it.

 

[bluesmoke99]

I have checked the hot and ground at the fuel pump there fine ive tried replacing the fuse with the fp connector disconnected still blows i removed fp relay and it still blows all before buying an ecm as well as i checked all the ecm to relay wiring and it also didnt show any issues the c2 plug on the ecm port 9 is the fuel pump relay switch side wiring and the ecm b is hot constantly as well as supplys the relay with power for when the ecm trips the relay ive done my homework ive got every schema i could find ive subscribed to alldata and i still cant find figure this out

 

[oldeerslayer]

You're going to have to start following wires until you find the short.
I'd start by following 20 and 57 from the PCM to the underhood fuse block. Have you unbolted section C2 from the underhood fuse block (UBEC) to see if any of the wires under there have rubbed against something? While you have it out start stripping the harness looking for damage as you go. Until you reach the PCM.