warning GMC SIERRA 2021 Owner's Manual

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
260 Driving and Operating
speed. The faster the vehicle speed, the
further back your vehicle will follow a
vehicle detected ahead. Consider traffic and
weather conditions when selecting the
following gap. The range of selectable gaps
may not be appropriate for all drivers and
driving conditions.
Changing the gap setting automatically
changes the alert timing sensitivity (Far,
Medium, or Near) for the Forward Collision
Alert (FCA) feature. SeeForward Collision
Alert (FCA) System 0275.
Alerting the Driver
With Head-Up Display
Without Head-Up Display If ACC is engaged, driver action may be
required when ACC cannot apply sufficient
braking because of approaching a vehicle
too rapidly.
When this condition occurs, the collision
alert symbol will flash on the windshield.
Either eight beeps will sound from the front,
or both sides of the Safety Alert Seat,
if equipped, will pulse five times. See
“Collision/Detection Systems”
underVehicle
Personalization 0131.
See Defensive Driving 0213.
Approaching and Following a Vehicle
The vehicle ahead indicator is in the
instrument cluster. It only displays when a
vehicle is detected in your vehicle’s path
moving in the same direction. If this symbol
is not displaying, ACC will not respond to or
brake for vehicles ahead.
ACC automatically slows the vehicle down
and adjusts vehicle speed to follow a
detected vehicle ahead at the selected following gap. The vehicle speed increases or
decreases to follow a detected vehicle in
front of your vehicle when that vehicle is
traveling slower than your vehicle set speed.
It may apply limited braking, if necessary.
When braking is active, the brake lamps will
come on. The automatic braking may feel or
sound different than if the brakes were
applied manually. This is normal.
Passing a Vehicle While Using ACC
If the set speed is high enough, and the left
turn signal is used to pass a vehicle ahead
in the selected following gap, ACC may
assist by gradually accelerating the vehicle
prior to the lane change.
{Warning
When using ACC to pass a vehicle or
perform a lane change, the following
distance to the vehicle being passed may
be reduced. ACC may not apply sufficient
acceleration or braking when passing a
vehicle or performing a lane change.
Always be ready to manually accelerate
or brake to complete the pass or lane
change.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 261
Stationary or Very Slow-Moving Objects
{Warning
ACC may not detect and react to stopped
or slow-moving vehicles ahead of you. For
example, the system may not brake for a
vehicle it has never detected moving. This
can occur in stop-and-go traffic or when a
vehicle suddenly appears due to a vehicle
ahead changing lanes. Your vehicle may
not stop and could cause a crash. Use
caution when using ACC. Your complete
attention is always required while driving
and you should be ready to take action
and apply the brakes.
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.
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” underVehicle
Personalization 0131.
When the vehicle ahead drives away, press
RES+ or the accelerator pedal to resume
ACC. If stopped for more than two minutes
or if the driver door is opened and the

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
262 Driving and Operating
driver seat belt is unbuckled, the ACC
automatically applies the Electric Parking
Brake (EPB) to hold the vehicle. The EPB
status light will turn on. SeeElectric Parking
Brake 0247.
A DIC warning message may display
indicating to shift to P (Park) before exiting
the vehicle. See Vehicle Messages 0130.
{Warning
If ACC has stopped the vehicle, and if ACC
is disengaged, turned off, or canceled, the
vehicle will no longer be held at a stop.
The vehicle can move. When ACC is
holding the vehicle at a stop, always be
prepared to manually apply the brakes.
{Warning
Leaving the vehicle without placing it in
P (Park) can be dangerous. Do not leave
the vehicle while it is being held at a
stop by ACC. Always place the vehicle in
P (Park) and turn off the ignition before
leaving the vehicle. ACC Override
If using the accelerator pedal while ACC is
active, the ACC indicator turns blue on the
instrument cluster and in the HUD,
if equipped, to indicate that automatic
braking will not occur. ACC will resume
operation when the accelerator pedal is not
being pressed.
{Warning
The ACC will not automatically apply the
brakes if your foot is resting on the
accelerator pedal. You could crash into a
vehicle ahead of you.
Curves in the Road
{Warning
On curves, ACC may not detect a vehicle
ahead in your lane. You could be startled
if the vehicle accelerates up to the set
speed, especially when following a vehicle
exiting or entering exit ramps. You could
lose control of the vehicle or crash. Do
not use ACC while driving on an entrance
or exit ramp. Always be ready to use the
brakes if necessary.
{Warning
On curves, ACC may respond to a vehicle
in another lane, or may not have time to
react to a vehicle in your lane. You could
crash into a vehicle ahead of you, or lose
control of your vehicle. Give extra
attention in curves and be ready to use
the brakes if necessary. Select an
appropriate speed while driving in curves.
ACC may operate differently in a sharp
curve. It may reduce the vehicle speed if the
curve is too sharp. ACC automatically slows
the vehicle down while navigating the curve
and may increase speed out of the curve,
but will not exceed the set speed.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
264 Driving and Operating
Weather Conditions Affecting ACC
If the interior temperature is extremely
high, the instrument cluster may indicate
that ACC is temporarily unavailable. This can
be caused by extreme hot weather
conditions with direct sunlight on the front
camera. ACC will return to normal operation
once the cabin temperature is lower.
Conditions that are associated with low
visibility, such as fog, rain, snow, or road
spray, may limit ACC performance. Water
droplets from rain or snow that remain on
the windshield may also limit ACC’s ability
to detect objects.
{Warning
Camera visibility may be limited and the
ACC system may not work properly if the
windshield is not clear. Do not use ACC if
moisture is present on the inside of the
windshield or the windshield washer is
used in cold weather. Turn on the front
defroster and make sure the windshield is
clear before using ACC. Before driving,
check that the windshield wipers are in
good condition and replace them if worn.Lighting Conditions Affecting ACC
The ACC front camera can be affected by
poor lighting conditions, and ACC may have
limited performance when:
.There are changes in brightness, such as
entering and exiting tunnels, bridges, and
overpasses.
.Low sun angles cause the camera to not
detect objects, or it is more difficult to
detect objects in the same traffic lane.
.Lighting is poor in the evening or early
morning
.There are multiple changes in brightness
or shadows along the vehicle roadway.
.In a tunnel without the headlamps on,
or in a tunnel when there is a vehicle in
front that does not have its taillamps on.
.Subjected to strong light from opposing
lane traffic in the front of the vehicle,
such as high-beam headlamps from
oncoming traffic.
Accessory Installations and Vehicle
Modifications
Do not install or place any object around
the front camera windshield area that would
obstruct the front camera view. Do not install objects on top of the vehicle
that overhang and obstruct the front
camera, such as a canoe, kayak, or other
items that can be transported on the
vehicle roof.
Do not modify the hood, headlamps, or fog
lamps, as this may limit the camera’s ability
to detect an object.
Cleaning the Sensing System
The camera sensor on the windshield behind
the rearview mirror can become blocked by
snow, ice, dirt, mud, or debris. This area
needs to be cleaned for ACC to operate
properly.
The vehicle headlamps may need to be
cleaned due to dirt, snow, or ice. Objects
that are not illuminated correctly may be
difficult to detect.
If ACC will not operate, regular cruise control
may be available. See
“Switching Between
ACC and Regular Cruise Control” previously
in this section. Always consider driving
conditions before using either cruise control
system.
For cleaning instructions, see “Washing the
Vehicle” underExterior Care 0398.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 265
Driver Assistance Systems
This vehicle may have features that work
together to help avoid crashes or reduce
crash damage while driving, backing, and
parking. Read this entire section before
using these systems.
{Warning
Do not rely on the Driver Assistance
Systems. These systems do not replace
the need for paying attention and driving
safely. You may not hear or feel alerts or
warnings provided by these systems.
Failure to use proper care when driving
may result in injury, death, or vehicle
damage. SeeDefensive Driving 0213.
Under many conditions, these systems
will not:
.Detect children, pedestrians, bicyclists,
or animals.
.Detect vehicles or objects outside the
area monitored by the system.
.Work at all driving speeds.
.Warn you or provide you with enough
time to avoid a crash. (Continued)
Warning (Continued)
.Work under poor visibility or bad
weather conditions.
.Work if the detection sensor is not
cleaned or is covered by ice, snow,
mud, or dirt.
.Work if the detection sensor is
covered up, such as with a sticker,
magnet, or metal plate.
.Work if the area surrounding the
detection sensor is damaged or not
properly repaired.
Complete attention is always required
while driving, and you should be ready to
take action and apply the brakes and/or
steer the vehicle to avoid crashes.
Audible or Safety Alert Seat
Some driver assistance features alert the
driver of obstacles by beeping. To change
the volume of the warning chime, see
“Comfort and Convenience” underVehicle
Personalization 0131. If equipped with the Safety Alert Seat, the
driver seat cushion may provide a vibrating
pulse alert instead of beeping. To change
this, see
“Collision/Detection Systems” under
Vehicle Personalization 0131.
Cleaning
Depending on vehicle options, keep these
areas of the vehicle clean to ensure the best
driver assistance feature performance. Driver
Information Center (DIC) messages may
display when the systems are unavailable or
blocked.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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Driving and Operating 267
1. View Displayed by the Rear VisionCamera
2. Corners of the Rear Bumper
Displayed images may be farther or closer
than they appear. The area displayed is
limited and objects that are close to either
corner of the bumper or under the bumper
do not display.
A warning triangle may display to show
that Rear Park Assist (RPA) has detected an
object. This triangle changes from amber to
red and increases in size the closer the
object.
If equipped with Hitch View, see “Surround
Vision” following.
Surround Vision
If equipped the Surround Vision system can
display various views surrounding the
vehicle in the infotainment display. See
below for camera view descriptions and
more information.
{Warning
The Surround Vision cameras have blind
spots and will not display all objects near
the corners of the vehicle. Folding outside
(Continued)
Warning (Continued)
mirrors that are out of position may not
display surround view correctly. Always
check around the vehicle when parking or
backing.
1. Views Displayed by the SurroundVision Cameras
2. Area Not Shown
1. Views Displayed by the Surround Vision Cameras
2. Area Not Shown
{Warning
The camera(s) do not display children,
pedestrians, bicyclists, crossing traffic,
animals, or any other object outside of
the cameras’ field of view, below the
bumper, or under the vehicle. Shown
distances may be different from actual
distances. Do not drive or park the
vehicle using only these camera(s).
Always check behind and around the
vehicle before driving. Failure to use
proper care may result in injury, death,
or vehicle damage.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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Driving and Operating 269
6. Guidance Lines/Hitch Guidance
Guidance Lines displays available
guidelines, including Standard and
Hitch Guidance. A grayed-out icon
indicates that guidelines are not
available. To enable, touch Guidance
Lines on the infotainment display
when a camera view is active.
Touching the button multiple times
will toggle through Standard
Guidelines, Hitch Guidance and no
guidelines. Standard guidelines are
available in Front/Rear Standard
Views, Front/Rear Top-Down Views
and Surround View.
Hitch Guidance displays a single
centered guideline on the
infotainment display to assist with
aligning the vehicle’s hitch ball with a
trailer coupler. Touch the Hitch
Guidance icon, then align the trailer
guidance line over the trailer coupler.
Continuously steer the vehicle to keep
the guideline centered on the coupler
when backing. Park Assist overlays will
not display when the trailer guidance
line is active. Hitch Guidance is
available in Rear Standard View.{Warning
Use Hitch Guidance only to help back the
vehicle to a trailer hitch or, when
traveling above 12 km/h (8 mph), to
briefly check the status of your trailer. Do
not use for any other purpose, such as
making lane change decisions. Before
making a lane change, always check the
mirrors and glance over your shoulder.
Improper use could result in serious
injury to you or others.
7. Interior Trailer View
Provides a view of the interior of the
trailer. The feature is available when a
trailer is connected. The feature
requires user installation of an
accessory trailer camera on the
interior of the trailer per the accessory
trailer camera installation instructions
(see your dealer for accessory trailer
camera(s) and information). To select,
touch Interior Trailer View on the
infotainment display when a camera
view is active. To access this view
when in a forward gear above
12 km/h (8 mph), touch CAMERA on
the infotainment display and touchthe Interior Trailer View icon. The view
will close after 8 seconds and can be
closed early by touching X.
8. Hitch View
Assists with connecting to a trailer by
providing a zoomed-in view of the
hitch to help align the vehicle’s hitch
ball with the trailer coupler, or to
monitor the trailer connection. To
select, touch Hitch View on the
infotainment display when a camera
view is active. To access this view
when in a forward gear above
12 km/h (8 mph), touch CAMERA on
the infotainment display and touch
the Cargo Bed View icon. The view
will close after 8 seconds and can be
closed early by touching X. Shifting
into P (Park) while in this view will
automatically engage the Electric
Parking Brake (EPB).
9. Bed View
Provides a view of the truck bed and
the area behind the vehicle to assist
in cargo or hitch monitoring or
hitching to a fifth wheel or gooseneck
trailer. To select, touch Bed View on
the infotainment display when a
camera view is active. To access this
view when in a forward gear above

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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Driving and Operating 273
.The accessory trailer camera is mounted,
angled or rotated outside of the defined
mounting location (see camera
installation instructions).
Distortion may be observed in the calibrated
Transparent Trailer View if:
.The accessory trailer camera is mounted,
angled or rotated outside of the defined
mounting location (see camera
installation instructions).
The Transparent Trailer icon may appear
grayed out if:
.A compatible trailer profile is not
configured or a non-compatible trailer
profile is selected.
.The vehicle is in R (Reverse).
.The trailer is not connected.
.The accessory rear trailer camera is not
connected or connected to the incorrect
input.
The preview may not be provided or the
wrong preview may be provided if:
.The accessory cameras are not recognized.
Ensure that the accessory camera(s) are
connected and power cycle the vehicle.
.The accessory trailer cameras are
swapped at the hitch connector. Ensure
that the accessory camera(s) are
connected to the correct input.
.The accessory trailer camera(s) are
connected to the correct camera input.
.The accessory trailer camera(s) are not
installed according to the installation
instructions.
A feature may be unavailable or not
activating as expected if:
.The customization is disabled. Check the
customization settings where applicable.
.The accessory trailer cameras are
swapped at the hitch connector. Ensure
that the accessory camera(s) are
connected to the correct camera input.
A view may switch automatically if:
.The vehicle is shifted to another gear.
Park Assist
With Front and Rear Park Assist, as the
vehicle moves at speeds of less than 8 km/h
(5 mph) the sensors on the bumpers may
detect objects up to 1.2 m (4 ft) in front and
2.5 m (8 ft) behind the vehicle within a zone
25 cm (10 in) high off the ground and below
bumper level. These detection distances may be shorter during warmer or humid weather.
Blocked sensors will not detect objects and
can also cause false detections. Keep the
sensors clean of mud, dirt, snow, ice, and
slush; and clean sensors after a car wash in
freezing temperatures.
{Warning
The Park Assist system does not detect
children, pedestrians, bicyclists, animals,
or objects located below the bumper or
that are too close or too far from the
vehicle. It is not available at speeds
greater than 8 km/h (5 mph). To prevent
injury, death, or vehicle damage, even
with Park Assist, always check the area
around the vehicle and check all mirrors
before moving forward or backing.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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274 Driving and Operating
The instrument cluster may have a Park
Assist display with bars that show“distance
to object” and object location information
for the Front and Rear Park Assist system.
As the object gets closer, more bars light up
and the bars change color from yellow to
amber to red.
When an object is first detected in the rear,
one beep will be heard from the rear,
or both sides of the Safety Alert Seat will
pulse two times. When an object is very
close —<0.4 m (1.5 ft) in the vehicle rear or
<0.3 m (1 ft) in the vehicle front —a
continuous beep will sound from the rear or
front depending on object location, or both
sides of the Safety Alert Seat will pulse five
times. Beeps for FPA are higher pitched than
for RPA.
Rear Cross Traffic Alert (RCTA)
If equipped, when the vehicle is shifted into
R (Reverse), RCTA shows a red warning
triangle with a left or right pointing arrow
on the infotainment display to warn of
traffic coming from the left or right. This
system detects objects coming from up to
20 m (65 ft) from the left or right side of
the vehicle. When an object is detected,
either three beeps sound from the left or right or three Safety Alert Seat pulses occur
on the left or right side, depending on the
direction of the detected vehicle.
Use caution while backing up when towing
a trailer, as the RCTA detection zones that
extend out from the back of the vehicle do
not move further back when a trailer is
towed.
RCTA is disabled when the trailer connection
status is displayed.
RCTA can be turned off. See
“Collision/
Detection Systems” underVehicle
Personalization 0131.
Turning the Features On or Off
PressXon the center stack to turn on or
off the Front and Rear Park Assist. The
indicator light next to the button comes on
when the features are on and turns off
when the features have been disabled. Front and Rear Park Assist can be turned
Off, On, or On with Towbar. See
“Park
Assist” underVehicle Personalization 0131.
If Park Assist is turned off through vehicle
personalization, the Park Assist button will
be disabled. To turn Park Assist on again,
select On in vehicle personalization. The On
with Towbar setting allows Park Assist to
work properly with a trailer hitch. Some
larger trailer hitches may not be compatible.
Turn off Park Assist when towing a trailer.
To turn the RPA symbols on or off, see
“Rear Camera Park Assist Symbols” under
Vehicle Personalization 0131.
Assistance Systems for Driving
If equipped, when driving the vehicle in a
forward gear, Forward Collision Alert (FCA),
Lane Departure Warning (LDW), Lane Keep
Assist (LKA), Side Blind Zone Alert (SBZA),
Lane Change Alert (LCA), Automatic
Emergency Braking (AEB), and/or the Front
Pedestrian Braking (FPB) System can help to
avoid a crash or reduce crash damage.

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Driving and Operating 275
Forward Collision Alert (FCA)
System
If equipped, the FCA system may help to
avoid or reduce the harm caused by
front-end crashes. When approaching a
vehicle ahead too quickly, FCA provides a
red flashing alert on the windshield and
rapidly beeps or pulses the driver seat. FCA
also lights an amber visual alert if following
another vehicle much too closely.
FCA detects vehicles within a distance of
approximately 60 m (197 ft) and operates at
speeds above 8 km/h (5 mph).
{Warning
FCA is a warning system and does not
apply the brakes. When approaching a
slower-moving or stopped vehicle ahead
too rapidly, or when following a vehicle
too closely, FCA may not provide a
warning with enough time to help avoid
a crash. It also may not provide any
warning at all. FCA does not warn of
pedestrians, animals, signs, guardrails,
bridges, construction barrels, or other(Continued)
Warning (Continued)
objects. Be ready to take action and
apply the brakes. SeeDefensive Driving
0 213.
FCA can be disabled through vehicle
personalization. See “Collision/Detection
Systems” underVehicle Personalization
0 131.
Detecting the Vehicle Ahead
FCA warnings will not occur unless the FCA
system detects a vehicle ahead. When a
vehicle is detected, the vehicle ahead
indicator will display green. Vehicles may
not be detected on curves, highway exit
ramps, or hills, due to poor visibility; or if a
vehicle ahead is partially blocked by
pedestrians or other objects. FCA will not
detect another vehicle ahead until it is
completely in the driving lane.
{Warning
FCA does not provide a warning to help
avoid a crash, unless it detects a vehicle.
FCA may not detect a vehicle ahead if
the FCA sensor is blocked by dirt, snow,
or ice, or if the windshield is damaged.
It may also not detect a vehicle on
winding or hilly roads, or in conditions
that can limit visibility such as fog, rain,
or snow, or if the headlamps or
windshield are not cleaned or in proper
condition. Keep the windshield,
headlamps, and FCA sensors clean and in
good repair.
Collision Alert
With Head-Up Display