2012 2500HD junction block failure

[BoatmanNH]

I think I have a junction block failure (fuse box) under the hood. I have no d/c power at all. Completely dead.
I only have a test light at the moment.  When I check the voltage going into the junction block the voltage is good. Coming out of the block the light is dim.  If I jump the two post I have power and my alarm goes off, etc.  Does the junction block need to be replace or am I missing something?  
 

thanks
 

 

[Formulabruce]

There should be plug in fuseable links in the junction box.

[BoatmanNH]

Can you elaborate?  I don’t believe the box can be open.