GMC 2003 GMT560 T-Series Owner's Manual page 74

With cruise control, you can maintain a speed of about
30 mph (48 km/h) or more without keeping your foot
on the accelerator. Cruise control does not work
at speeds below about 30 mph (48 km/h).
If you have an automatic transmission and you apply
your brakes, the cruise control will shut off.
If you have a manual transmission and you apply your
brakes or push the clutch pedal, the cruise control
will shut off.
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CAUTION:
•
Cruise control can be dangerous where
you can't drive safely at a steady speed.
So, don't use your cruise control on
winding roads or in heavy traffic.
•
Cruise control can be dangerous on
slippery roads. On such roads, fast
changes in tire traction can cause
needless wheel spinning, and you could
lose control. Don't use cruise control on
slippery roads.
3-10
Setting Cruise Control
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CAUTION:
If you leave your cruise control on when you're
not using cruise, you might hit a button and go
into cruise when you don't want to. You could
be startled and even lose control. Keep the
cruise control switch off until you want to use
cruise control.
1. Move the cruise control switch to on.
2. Get up to the speed you want.
3. Press in the set button at the end of the lever and
release it.
4. Take your foot off the accelerator pedal. The
accelerator pedal will not go down.