Chevrolet 2004 Impala Owner's Manual page 134

4. Take your foot off the accelerator.
The CRUISE light on the instrument panel cluster will
come on after the cruise control has been set to
the desired speed.
3-12
3. Press the SET button
located on the steering
wheel and release it.
Resuming a Set Speed
Suppose you set your cruise control at a desired speed
and then you apply the brake. This, of course shuts
off the cruise control. But you don't need to reset it.
Once you're going about
25 mph (40 km/h) or more,
press the RESUME
button on your steering
wheel. You'll go right back
up to your chosen
speed and stay there.