[777stickman]

Looking at my '98 C/K manual I can only see 2 things the ECM B fuse powers, although there may be more. The ECM B fuse is "hot at all times".

1. Powers the fuel pump thru the "energized" contacts of the fuel pump relay.
2. Supplies 12v power to the VCM/PCM.

Since you have removed the fuel pump relay and it still blows the next thing to check is the VCM.

There are 4 connectors at the VCM. The one that has the ECM B feed is the one labled "white" (top fwd). Pull this connector off and install a new ECM B fuse and see what happens.

If the fuse blows then there is probably a worn spot in the wire shorting directly to ground. If it does not blow, wiggle the harness around and if still does not blow then remove the fuse and reconnect the "white" VCM connector. Reinstall the fuse. If it blows then it's most likely an internal short in the VCM.

Hope this helps and please post back what you find.

Cheers from another old aircraft mechanic...........Steve