GMC 2010 Sierra - Manual (Page 163)

B (ACC/ACCESSORY): This position lets things like
the radio and the windshield wipers operate while the
engine is off. Use this position if the vehicle must be
pushed or towed.
C (ON/RUN): This position can be used to operate the
electrical accessories and to display some instrument
panel cluster warning and indicator lights. The switch
stays in this position when the engine is running. The
transmission is also unlocked in this position on
automatic transmission vehicles.
If you leave the key in the ACC/ACCESSORY or
ON/RUN position with the engine off, the battery
could be drained. You may not be able to start the
vehicle if the battery is allowed to drain for an
extended period of time.
D (START): This is the position that starts the engine.
When the engine starts, release the key. The ignition
switch returns to ON/RUN for driving.
A warning tone will sound when the driver door is
opened, the ignition is in ACC/ACCESSORY or
LOCK/OFF and the key is in the ignition.
Retained Accessory Power (RAP)
The following vehicle accessories can be used for up to
10 minutes after the engine is turned off:
. Audio System
. Power Windows
. OnStar ® System (if equipped)
. Sunroof (if equipped)
These features work when the key is in ON/RUN or
ACC/ACCESSORY. Once the key is turned from ON/
RUN to LOCK/OFF, the windows and sunroof continue
to work up to 10 minutes until any door is opened. The
radio continues to work for up to 10 minutes or until the
driver door is opened.
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