Chevy & GMC Vans

Are they different than normal DTC codes form the scan tool? I have several scan tools and both are saying no DTC but I have an intermittant ABS light and random odd brake behavior. I know something id going on but can't figure out what especially if I can't find a code from the ABS system.

Figured it out. My old scan tools simply don't read the ABS codes. Ordered a new blue tooth scan tool that should handle my needs well into the future. Always something..