Brake System Warning Light - GMC Sierra Denali 2009 Owner's Manual

The voltmeter gage may also read lower when in fuel
economy mode. This is normal.
Readings in the low warning zone can occur when a
large number of electrical accessories are operating in
the vehicle and the engine is left at an idle for an
extended period. This condition is normal since the
charging system is not able to provide full power
at engine idle. As engine speeds are increased, this
condition should correct itself as higher engine speeds
allow the charging system to create maximum power.
The vehicle can only be driven for a short time with the
reading in either warning zone. If the vehicle must
be driven, turn off all unnecessary accessories.
Readings in either warning zone indicate a possible
problem in the electrical system. Have the vehicle
serviced as soon as possible.

Brake System Warning Light

With the ignition on, the brake system warning light
comes on when the parking brake is set. If the vehicle
is driven with the parking brake engaged, a chime
sounds when the vehicle speed is greater than 5 mph
(8 km/h).
3-38
The vehicle's hydraulic brake system is divided into two
parts. If one part is not working, the other part can
still work and stop the vehicle. For good braking, both
parts need to be working well.
If the warning light comes on and a chime sounds there
could be a brake problem. Have the brake system
inspected right away.
This light can also come on due to low brake fluid. See
Brakes on page 5-38 for more information.
United States
This light comes on briefly when the ignition key is
turned to ON/RUN. If it does not come on then, have it
fixed so it is ready to warn if there is a problem.
Canada