GMC 2010 Yukon/Yukon XL Owner's Manual page 231

If the cruise control system is already activated,
Press and hold the +RES button on the steering
wheel until the desired speed is reached, then
release it.
To increase vehicle speed in small amounts,
press the +RES button. Each time this is done,
the vehicle goes about 1.6 km/h (1 mph) faster.
If the cruise control system is already activated,
Press and hold the SET button on the steering
wheel until the desired lower speed is reached,
then release it.
To slow down in small amounts, press the SET
button on the steering wheel briefly. Each time this
is done, the vehicle goes about 1.6 km/h (1 mph)
slower.
Use the accelerator pedal to increase the vehicle
speed. When you take your foot off the pedal, the
vehicle will slow down to the previous set cruise speed.
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 turns off.
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.
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