GMC 1999 Sierra 1500 Pickup Owner's Manual page 118

.Featurns & Controls
I
To Increase Speed While Using Cruise Control
There are two ways to go
to a higher speed. Here's the first:
1. Use the accelerator pedal to get to the higher speed.
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2. Push the button at the end of the lever, then release the button and the
accelerator pedal.
You'll now cruise at the higher speed.
Here's the Second Way to go to a higher speed:
1.
Move the Cruise switch from ON to WA. Hold it there until you get up
to the speed you want, and then release the switch.
2. To
increase your speed in very small amounts, move the switch to WA
for less than half a second and then release it. Each time you do this,
your vehicle will go about 1 mph (1.6 km/h) faster.
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