2006 GMC Sierra 1500 Pickup Owner's Manual - Page 239

SERVICE 4WD (Four-Wheel-Drive) If a problem occurs with the four-wheel-drive system, this message will appear 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 four-wheel-drive system needs service. See your GM dealer. SERVICE BRAKE BOOSTER {CAUTION: Your brake system may not be working properly if the SERVICE BRAKE BOOSTER message is displayed. If the brake system warning light is also on, you should have the vehicle towed for service. See Brake System Warning Light on page 3-41. If the brake system warning light is not on, you still have brakes, but the supplemental brake assist system on vehicles with rear disc brakes may not operate properly. In the event of a vacuum loss, you may not have vacuum power assist for braking. The brake pedal will be harder to push and it will take longer to stop. If you continue to drive with this message displayed it can lead to a crash. Have the brake system serviced as soon as possible. If your vehicle has vacuum assist power brakes, this message will be displayed on the DIC when there is a problem with the Supplemental Brake Assist system. 3-61 SERVICE AIRBAG If there is a problem with the airbag system, this message will be displayed on the DIC. Have your GM dealer inspect the system for problems. See Airbag Readiness Light on page 3-35 and Airbag System on page 1-70 for more information. Pressing any of the four DIC buttons will acknowledge the message and clear it from the DIC display. If your vehicle does not have the four DIC buttons, pressing the trip odometer reset stem will acknowledge the message and clear it from the DIC display.