Tried using the Jumper/Terminal block in the engine compartment on my '05 the other day and got nada.
There is 12vdc at the terminal, but the GRND portion of the bracket was no good.
GM was overzealous with the powder coating on the ground bracket.
Had to remove the bracket and wire-wheel the powder coating off the bolt end of the bracket to establish good ground continuity.
Before you find it necessary to jump-start a Powerstroke or Cummin's, best check your GRND bracket, otherwise you'll be clamping the ground lead of your jumper cables to something else to get things to work. Not a big problem, but if it's there for the jumper cable clamp, it really oughta work.

there really shouldnt be anything on the ground bracket. dont know why gm would powdercoat it at all. at least you figured it out.

You got that right, they left the flat section with 'GRND' stamped on it free of powder coating, but they coated it pretty heavily on the rest of the bracket. Must've just been for looks I guess.

yeah im sure it was for looks but obviously it was a stupid thing to do. my 02' didnt have anything on it but i bought it used maybe is WAS powdercoated.

there really shouldnt be anything on the ground bracket. dont know why gm would powdercoat it at all. at least you figured it out.

And then they leave several undercarriage components (driveshaft, etc.) bare metal. Boggles the mind . . .

They been doing that to the ground jumper since 01.
Go figure that one out!