GMC SIERRA 2020 Owner's Manual page 252

Irregular Objects Affecting ACC
ACC may have difficulty detecting
the following objects:
Vehicles in front of your vehicle
that have a rear aspect that is
low, small, or irregular
An empty truck or trailer that has
no cargo in the cargo bed
Vehicles with cargo extending
from the back end
Non-standard shaped vehicles,
such as vehicle transport,
vehicles with a side car fitted,
or horse carriages
Vehicles that are low to the road
surface
Objects that are close to the
front of your vehicle
Vehicles on which extremely
heavy cargo is loaded in the
cargo area or rear seat
ACC Automatically Disengages
ACC may automatically disengage
and the driver will need to manually
apply the brakes to slow the
vehicle if:
The front camera is blocked or
visibility is reduced.
The Traction Control System
(TCS) or StabiliTrak/ESC system
has activated or been disabled.
There is a fault in the system.
A DIC message displays to
indicate that ACC is temporarily
unavailable.
The ACC indicator will turn white
when ACC is no longer active.
Driving and Operating
In some cases, when ACC is
temporarily unavailable, regular
cruise control may be used. See
Switching Between ACC and
Regular Cruise Control previously
in this section. Always consider
driving conditions before using
either cruise control system.
Notification to Resume ACC
ACC will maintain a follow gap
behind a detected vehicle and slow
your vehicle to a stop behind that
vehicle.
If the stopped vehicle ahead has
driven away and ACC has not
resumed, the vehicle ahead
indicator will flash as a reminder to
check traffic ahead before
proceeding. In addition, the left and
right sides of the Safety Alert Seat
will pulse three times, or three
beeps will sound. See Alert Type
and Adaptive Cruise Go Notifier in
Collision/Detection Systems under
Vehicle Personalization 0 156.
When the vehicle ahead drives
away, press RES+ or the
accelerator pedal to resume ACC.
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