Circuit/System Verification
WARNING: This page is about a different car, the 2010 GMC Terrain and 2010 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
Ignition ON, observe the scan tool Brake Pressure Sensor parameter. The reading should be 0 V, when the brake pedal is released and greater than 1 V, when the brake pedal is applied.