i had a friend put a scanner on my 1999 Suburban and it won't turn over. help

Check connections, state of charge, power to the start enable pigtail wire, put it in park and step on the brake. If you thoroughly check it and cannot resolve, check circuit protections like fusible links, inline fuses or if you have a poer distribution box, follow and trace cables to it and check connections and test fuses inside.

Excuse, please, (power distribution) and start enable pigtail powers up when all driver controls are set and the ignition is cranked. You have to look at what is supplied for parts on your rig and act accordingly. A schematic may be found thru Autozone but be specific and be sure what ones you pick.

In automotive terms, "won't turn over" means engine fails to crank. Is that what it is doing? Or cranks but wont start? or cranks, tries to start and dies.

The schematics can be found thru a search of the website.