ACC Unavailable Warning
If the system turns off, and the EVIC displays “Adaptive Cruise Control (ACC) Unavailable”, there may be a temporary malfunction that limits ACC functionality.
Although the vehicle is still drivable under normal conditions, ACC will be temporarily unavailable. If this occurs, try activating ACC again later, following a key cycle. If the problem persists, see your authorized dealer.

Adaptive Cruise Control (ACC) Unavailable Warning
See also:
Security System Manual Override
The Vehicle Security Alarm will not arm if you lock the
doors using the manual door lock plunger. ...
Trailer And Tongue Weight
Always load a trailer with 60% to 65% of the weight in
the front of the trailer. This places 10% of the Gross Trailer
Weight (GTW) on the tow hitch of your vehicle. Loads
balanced over the wheel ...
Power-Up
After switching the ignition key from OFF to either the
ON or ACC position, or after a language change, you
must wait at least fifteen seconds prior to using the
system.
...
