GMC Sierra Denali Classic 2007 Owner's Manual page 196

SERVICE 4WD (Four-Wheel-Drive)
If a problem occurs with the all-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 all-wheel-drive system
needs service. See your dealer. Pressing any of
the four DIC buttons or the trip odometer reset
stem will acknowledge the message and clear it
from the DIC display.
SERVICE AIRBAG
If there is a problem with the airbag system, this
message will be displayed on the DIC. Have
your dealer inspect the system for problems. See
Airbag Readiness Light on page 171 and
Airbag System on page 64 for more information.
Pressing any of the four DIC buttons or the
trip odometer reset stem will acknowledge the
message and clear it from the DIC display.
196
SERVICE BRAKE BOOSTER
CAUTION:
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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 176.
If the brake system warning light is not
on, you still have brakes, but the
supplemental brake assist system 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.