GM Service Manual Online
For 1990-2009 cars only

Hydraulic Booster Functional Test for Chevrolet Chevy P42 Commercial Chassis 1997

With the ignition switch in the "OFF" position, apply the brake pedal several times to empty the accumulator. Apply the brake pedal using 180 N (40 lb) of force and start the engine. The pedal should fall and then push back against your foot.