I too know this is old, but this thread came up on a google search for this problem and the poster directly above helped my issue with my 02 Suburban. Hope my experience will help someone avoid hours of backbreaking work removing rusted on rear rotors to get to the star adjusters.
I couldn't get a vice grips on the cable inside the truck (not enough room) so I engaged the parking brake then clamped the parking brake cable with a vice grips just aft of the equalizer where it enters another sheath. I had to engage my pedal about 3/4 of the way before the autoadjuster would start to do its thing.
The truck now holds nice and steady, although the pedal does go almost all the way to the floor. Thanks, Dan B.!!