Bleeding the brake system after changing the brakes can be hard on some anti-lock braking systems. The good news is that on some GM vehicles, a scan tool isn’t needed to bleed ABS brakes. A scan tool is only needed with a DBC-7 anti-lock braking system, and then only if air entered the ABS modulator during brake service. The GM vehicles using the DBC-7 system include many recent Chevy and Pontiac cars, so check with your manual or dealer to see which braking system your GM vehicle has.
Open the front bleeder screw on the modulator. There are two screws, open the one at the front. Bleed the brakes by having another person gradually press on the brake pedal until all air is purged and clean fluid flows. Attaching a clear tube to the bleeder valve and placing the other end in a container of fluid helps.