GMC 2010 Sierra 1500 Crew Cab Owner's Manual page 233

If the cruise control is set at a desired speed and then
the brakes are applied, the cruise control is disengaged
without erasing the set speed from memory.
Once the vehicle speed reaches about 40 km/h
(25 mph) or more, press the +RES button on the
steering wheel. The vehicle returns to the previous set
speed and stays there.
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.
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