Cadillac 2011 DTS Owner's Manual page 170

FCA is enabled when the green light on the button
is lit. FCA is disabled when the indicator light is
amber.
On winding roads, FCA may not detect a
vehicle ahead. You could crash into a vehicle
ahead of you. Do not rely on FCA on winding
roads.
When weather limits visibility, such as in fog,
rain, or snow, FCA performance is limited.
There may not be enough warning distance to
the vehicle in front of you. Do not rely on FCA
in low visibility conditions.
4-8
When FCA is enabled, the Adaptive Cruise
Control switch is on. If you press another Adaptive
Cruise Control button, you might go into cruise
when you do not want to. You could be startled
and even lose control. Be careful not to press
adaptive cruise buttons unless you want to use
cruise control.
The FCA alert symbol will
flash and a warning beep
will sound when driver
action may be required.