GMC 2011 Sierra - Manual (Page 220)

Black plate (4,1) GMC Sierra Owner Manual - 2011
6-4 Lighting
Daytime Running
Lamps (DRL)
Daytime Running Lamps (DRL) can
make it easier for others to see the
front of your vehicle during the day.
Fully functional daytime running
lamps are required on all vehicles
first sold in Canada.
The DRL system comes on when
the following conditions are met:
. The ignition is on.
. The exterior lamps control is
in AUTO.
. The transmission is not in Park.
. The light sensor determines it is
daytime.
When the DRL system is on,
only the DRL lamps are on.
The taillamps, sidemarker,
instrument panel lights, and
other lamps will not be on.
When it begins to get dark, the
automatic headlamp system
switches from DRL to the
headlamps.
To turn off the DRL lamps, turn
the exterior lamps control to the
OFF position and then release.
For vehicles first sold in Canada,
the transmission must be in the
P (Park) position before the DRL
lamps can be turned off.
Automatic Headlamp
System
When it is dark enough outside, the
automatic headlamp system turns
on the headlamps at the normal
brightness, along with the taillamps,
sidemarker, parking lamps, and the
instrument panel lights. The radio
lights will also be dim.
To turn off the automatic headlamp
system, turn the exterior lamps
switch to the off position and then
release it. For vehicles first sold in
Canada, the transmission must be
in the P (Park) position before the
automatic headlamp system can
be turned off.
The vehicle has a light sensor
located on the top of the instrument
panel which regulates when the
automatic headlamps turn on.
Do not cover the sensor, otherwise
the headlamps will come on
whenever the ignition is on.
The system may also turn on the
headlamps when driving through a
parking garage or heavy overcast
weather. This is normal.
There is a delay in the transition
between the daytime and
nighttime operation of the Daytime
Running Lamps (DRL) and the
automatic headlamp systems
so that driving under bridges
or bright overhead street lights
does not affect the system.