Voltmeter Gage; Brake System Warning Light - GMC 2009 Yukon XL Owner's Manual

Voltmeter Gage

When the engine is running, the gage shows the
condition of the charging system. The charging system
regulates voltage based on the state of the battery
for improved fuel economy and battery life. The gage
may transition from a higher to lower or a lower to higher
reading, this is normal. Readings between the low
and high warning zones indicate the normal operating
range. The gage may also read low during the fuel
economy mode, this is normal.
3-40
When the engine is not
running, but the ignition is
on, this gage shows
the battery's state of
charge in DC volts.
Readings in the low warning zone may 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 full power. If there is
a problem with the battery charging system, this light will
come on or the SERVICE BATTERY CHARGING
SYSTEM DIC message will display. See DIC Warnings
and Messages on page 3-64 and Charging System Light
on page 3-39 for more information.

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).
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.