Chevrolet 2005 Tahoe Owner's Manual page 195

If the warning light comes on and a chime sounds there
could be a brake problem. Have your brake system
inspected right away.
United States
This light should come on briefly when you turn the
ignition key to RUN. If it doesn't come on then,
have it fixed so it will be ready to warn you if there's
a problem.
If the light comes on while you are driving, pull off the
road and stop carefully. You may notice that the pedal is
harder to push or may go closer to the floor. It may
take longer to stop. If the light is still on, have the
vehicle towed for service. See Towing Your Vehicle on
page 4-57.
Canada
CAUTION:
{
Your brake system may not be working
properly if the brake system warning light is
on. Driving with the brake system warning light
on can lead to an accident. If the light is still
on after you have pulled off the road and
stopped carefully, have the vehicle towed
for service.
3-43