Voltmeter Gage; Brake System Warning Light - GMC Yukon XL Denali 2005 Owner's Manual

Voltmeter Gage

When the engine is running, the gage shows the
condition of the charging system. 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.
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 maximum power.
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When your engine is not
running, but the ignition is
in RUN, this gage
shows your battery's state
of charge in DC volts.
You can only drive for a short time with the reading in
either warning zone. If you must drive, 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 will
flash when you set the parking brake. The light will flash if
the parking brake doesn't release fully. If you try to drive
with the parking brake engaged, a chime will sound when
the vehicle speed is greater than 3 mph (5 km/h).
Your vehicle's hydraulic brake system is divided into two
parts. If one part isn't working, the other part can still
work and stop you. For good braking, though, you need
both parts working well.
If the warning light comes on and a chime sounds there
could be a brake problem. Have your brake system
inspected right away.