GMC 1999 Suburban Owner's Manual page 109

Reducing Speed While Using Cruise Control
There are two ways to reduce your speed while using
cruise control:
D
Push in the SET button at the end of the lever until
you reach the lower speed you want, then release it.
D
To slow down in very small amounts, push the
button for less than half a second. Each time you do
this, you'll go 1 mph (1.6 km/h) slower.
Passing Another Vehicle While Using Cruise Control
Use the accelerator pedal to increase your speed. When
you take your foot off the pedal, your vehicle will slow
down to the cruise control speed you set earlier.
Using Cruise Control on Hills
How well your cruise control will work on hills depends
upon your speed, load and the steepness of the hills.
When going up steep hills, you may have to step on the
accelerator pedal to maintain your speed. If the
steepness of the hill causes the vehicle speed to drop
more than 15 mph (24 km/h) below the set speed, your
cruise control will automatically disengage. When going
downhill, you may have to brake or shift to a lower gear
to keep your speed down. Of course, applying the brake
takes you out of cruise control. Many drivers find this to
be too much trouble and don't use cruise control on
steep hills.
Ending Cruise Control
There are two ways to turn off the cruise control:
D
Step lightly on the brake pedal or
D
Move the cruise control switch to OFF.
Erasing Speed Memory
When you turn off the cruise control or the ignition,
your cruise control set speed memory is erased.
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