GMC 2010 Sierra 1500 Crew Cab Owner's Manual page 234

How well the cruise control will work on hills depends
upon the vehicle speed, load, and the steepness of the
hills. When going up steep hills, you might have to step
on the accelerator pedal to maintain the vehicle speed.
When going downhill, you might have to brake or shift
to a lower gear to keep the vehicle speed down. When
the brakes are applied the cruise control is disengaged.
There are three ways to end cruise control:
To disengage cruise control; step lightly on the
brake pedal.
Press on the steering wheel.
To turn off the cruise control, press
steering wheel.
The cruise control set speed is erased from memory by
pressing the button or if the ignition is turned off.
4-10
It controls the following systems:
Headlamps
Taillamps
Parking Lamps
on the
License Plate Lamps
Instrument Panel Lights
The exterior lamps control has four positions:
daytime running lamps (DRL). Turn the headlamp
control to the off position again to turn the automatic
headlamps or DRL back on.
For vehicles first sold in Canada, the off position will
only work when the vehicle is shifted into P (Park).
The exterior lamps
control is located on the
instrument panel to the
left of the steering wheel.
Turns off the automatic headlamps and