AC Delco TDS (Technical Delivery System) is the bizzaro-land name for the parallel universe you must enter if you want to get actual useful information from GM.
Don’t bother going to GM.com or contacting them — although amazingly you can, with persistence, get through to someone even on a Saturday afternoon with grease on your fingers. They will try to brain-drain you for their CRM-filling, and then ask you helpful things like, “have you looked in the owner’s manual?”
The actual stuff you want: service manuals, technical bulletins, wiring diagrams, diagnostic procedures, specifications, etc. are actually pretty darn good within AC Delco TDS.
It costs $20 for a three-day online subscription. You can’t reliably capture or print out the information (you can use browser-level print etc.). There are, however, for most diagrams, good vector graphics that you can use (their proprietary shitty in-browser crippleware viewer) to zoom in on.
Good luck to you!