GMC Sierra Classic 2007 Owner's Manual page 275

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 252.
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. If the message is displayed
immediately after starting the vehicle or the
message appears while driving, the Supplemental
Brake Assist system needs service. See your
dealer. See Brake System Warning Light on
page 252 for additional information.
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. See your dealer.
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