2003 GMC Sierra 1500 Pickup Owner's Manual - Page 217

SERVICE BRAKE SYSTEM If there is a problem with the brake system, this message will be displayed on the DIC. If this message appears, stop as soon as possible and turn off the vehicle. Restart the vehicle and check for the message on the DIC display. If the message is still displayed, or appears again when you begin driving, the brake system needs service. Your brake s tem may not be working properly if the SERVICE BRAKE BOOSTER message is displayed. If the brake system warning light is on, you also should have the vehicle towed for service. See "Brake System Warning Light" in the Index. SERVICE BRAKE BOOSTER If your vehicle has vaccum assist power brakes, this message will be displayed on the DIC when there is a problem with the Supplemental Brake Assist system. If the message is displayed immediately after starting the vehicle or the message appears while driving, your Supplemental Brake Assist system needs service. See Brake System Warning Light on page 3-40. If the brake system warning isn't on, you light still have brakes, but the supplemental brake In the assist system may not operate properly. event of a vacuum loss, you may not have vacuum power assist for braking. brake The pedal will be harder to push it will take and longer to stop. If you continue to drive with th message displayedit can leadto a crash.Have the brake system serviced soon as possible. as 3-62