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GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 247
Using ABS
Do not pump the brakes. Just hold the brake
pedal down firmly. Hearing or feeling ABS
operate is normal.
Braking in Emergencies
ABS allows steering and braking at the same
time. In many emergencies, steering can
help even more than braking.
Electric Parking Brake
The Electric Parking Brake (EPB) can always
be applied, even if the vehicle is off. In case
of insufficient electrical power, the EPBcannot be applied or released. To prevent
draining the battery, avoid unnecessary
repeated cycles of the EPB.
The system has a red parking brake status
light and an amber service parking brake
warning light. See
Electric Parking Brake
Light 0117 and
Service Electric Parking Brake Light 0118.
There are also parking brake-related Driver
Information Center (DIC) messages.
Before leaving the vehicle, check the red
parking brake status light to ensure that the
parking brake is applied.
EPB Apply
To apply the EPB:
1. Be sure the vehicle is at a complete stop.
2. Press the EPB switch momentarily.
The red parking brake status light will flash
and then stay on once the EPB is fully
applied. If the red parking brake status light
flashes continuously, then the EPB is only
partially applied or there is a problem with
the EPB. A DIC message will display. Release
the EPB and try to apply it again. If the
light does not come on, or keeps flashing, have the vehicle serviced. Do not drive the
vehicle if the red parking brake status light
is flashing. See your dealer.
If the amber service parking brake warning
light is on, press the EPB switch. Continue to
hold the switch until the red parking brake
status light remains on. If the amber service
parking brake warning light is on, see your
dealer.
If the EPB is applied while the vehicle is
moving, the vehicle will decelerate as long
as the switch is pressed. If the switch is
pressed until the vehicle comes to a stop,
the EPB will remain applied.
The vehicle may automatically apply the EPB
in some situations when the vehicle is not
moving. This is normal, and is done to
periodically check the correct operation of
the EPB system, or at the request of other
safety functions that utilize the EPB.
If the EPB fails to apply, block the rear
wheels to prevent vehicle movement.
EPB Release
To release the EPB:
1. Turn the ignition on or to ACC/ ACCESSORY.
2. Apply and hold the brake pedal.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
248 Driving and Operating
3. Press the EPB switch momentarily.
The EPB is released when the red parking
brake status light is off.
If the amber service parking brake warning
light is on, release the EPB by pressing and
holding the EPB switch. Continue to hold the
switch until the red parking brake status
light is off. If either light stays on after
release is attempted, see your dealer.
Caution
Driving with the parking brake on can
overheat the brake system and cause
premature wear or damage to brake
system parts. Make sure that the parking
brake is fully released and the brake
warning light is off before driving.
If you are towing a trailer and parking on a
hill, see Driving Characteristics and Towing
Tips 0288.
Automatic EPB Release
The EPB will automatically release if the
vehicle is running, placed into gear, and an
attempt is made to drive away. Avoid rapid
acceleration when the EPB is applied, to
preserve parking brake lining life.
Brake Assist
Brake Assist detects rapid brake pedal
applications due to emergency braking
situations and provides additional braking to
activate the Antilock Brake System (ABS) if
the brake pedal is not pushed hard enough
to activate ABS normally. Minor noise, brake
pedal pulsation, and/or pedal movement
during this time may occur. Continue to
apply the brake pedal as the driving
situation dictates. Brake Assist disengages
when the brake pedal is released.
Hill Start Assist (HSA)
{Warning
Do not rely on the HSA feature. HSA does
not replace the need to pay attention
and drive safely. You may not hear or
feel alerts or warnings provided by this
system. Failure to use proper care when
driving may result in injury, death,
or vehicle damage. See Defensive Driving
0 213.
When the vehicle is stopped on a grade, Hill
Start Assist (HSA) prevents the vehicle from
rolling in an unintended direction during the
transition from brake pedal release to accelerator pedal apply. The brakes release
when the accelerator pedal is applied. If the
accelerator pedal is not applied within a few
minutes, the Electric Parking Brake will
apply. The brakes may also release under
other conditions. Do not rely on HSA to hold
the vehicle.
HSA is available when the vehicle is facing
uphill in a forward gear, or when facing
downhill in R (Reverse). The vehicle must
come to a complete stop on a grade for HSA
to activate.
Ride Control Systems
Traction Control/Electronic
Stability Control
System Operation
The vehicle has a Traction Control System
(TCS) and StabiliTrak/Electronic Stability
Control (ESC) system. These systems help
limit wheel spin and assist the driver in
maintaining control, especially on slippery
road conditions.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 251
5must be pressed again to re-enable HDC.
HDC may disable after an extended period
of use. If this happens, HDC will require
time to cool down. The length of time HDC
remains active depends on road conditions,
grade, set speed, vehicle loading, and
outside temperature.
When enabled, if the vehicle speed is above
30 km/h (19 mph) and below 60 km/h
(37 mph), a DIC message will display.
Driver Mode Control
Driver Mode Control (DMC) allows the driver
to adjust the overall driving experience to
better suit preference by adjusting multiple
systems to fit specific driving needs. Drive
mode availability and affected vehicle
subsystems are dependent upon vehicle trim
level, region, and optional features.
Mode Activation
To activate Tow/Haul Mode turn the knob
counterclockwise. To activate other drive
modes turn the knob clockwise.
If equipped, select Terrain Mode by
pressing the
gbelow the 4mtransfer
case button.
Modes:
Normal Mode : Use for normal city and
highway driving to provide a smooth ride.
This setting provides balance between
comfort and handling. This is the standard/
default mode. There is no persistent
indicator in the instrument cluster for
this mode.
8Sport Mode : Use where road conditions
or personal preference demand a more
controlled response.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
252 Driving and Operating
When you enter this mode, you will
immediately feel a down shift. In this mode
the vehicle also monitors driving behaviors
and automatically enables Performance Shift
Features when spirited driving is detected.
These features maintain lower transmission
gears to increase available engine braking
and improve acceleration response. The
vehicle will exit these features and return to
normal operation after a short period when
spirited driving is no longer detected. If the
vehicle has Magnetic Ride Control, the
suspension will change to provide better
cornering performance.
6Snow/Ice Mode :Snow/Ice Mode
improves vehicle acceleration on snow and
ice covered roads. When active, Snow/Ice
Mode will adjust acceleration to optimize
traction on slippery surfaces. This can
compromise the acceleration on dry asphalt.
This feature is not intended for use when
the vehicle is stuck in sand, mud, ice, snow,
or gravel. If the vehicle becomes stuck, see If
the Vehicle Is Stuck 0221.
7Off-Road Mode : Use this mode for
off-road recreational driving. Off-Road Mode
should be used to improve driving at
moderate speeds, on grass, gravel, dirt,
unpaved roads, or snow-covered roads. The accelerator pedal is tuned for off-road use.
This mode modifies pedal mapping,
All-Wheel Drive (AWD), ride height, Antilock
Brake System (ABS), StabiliTrak/Electronic
Stability Control (ESC), and Traction Control
System (TCS) performance.
For more information on off-road driving see
Off-Road Driving
0215.
_Tow/Haul Mode : Use this mode
when hauling heavy loads to provide
increased performance and vehicle control.
Tow/Haul Mode adjusts the transmission
shift pattern, AWD, and ESC performance.
If the vehicle is turned off with Tow/Haul
Mode active and then restarted within four
hours or less, Tow/Haul will remain active.
Otherwise, the vehicle will start in
Normal Mode.
If the vehicle has a diesel engine, exhaust
braking is automatically activated when
Tow/Haul Mode is selected. It maintains
vehicle speed by automatically
implementing a shift pattern that uses the
engine and the transmission to slow the
vehicle. The system will command
downshifts and use the turbocharger on the
engine to reduce vehicle speed when the
brake is applied. The normal tow/haul shift pattern will return once the vehicle is on a
low grade or when the accelerator pedal is
pressed.
While in the Electronic Range Select (ERS)
Mode (see
“manual mode”), grade breaking
is deactivated, allowing the driver to select a
range and limiting the highest gear
available.
For more information on trailer weight
specifications, see Towing Equipment 0296.
gTerrain Mode : Use for finer control
during low speed, off-road driving. When
using this mode it will mimic the
characteristics of four-wheel-drive low (4
n)
without the torque capabilities.
Use when:
.Traveling on very rough roads at very low
speeds, such as a two-track or heavily
rutted road.
.Traveling slowly in grassy fields.
.Pulling a boat out of the water on a
trailer.
.Using the vehicle for public off-road
recreational driving. See Off-Road Driving
0 215 and
Hill and Mountain Roads 0219.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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254 Driving and Operating
Terrain Mode is only available on vehicles
equipped with the single speed
transfer case.
Terrain Mode can only be active when:
.Vehicle speed is less than 80 km/h
(50 mph).
.The transfer case is in 4m.
Frequent use of this mode may cause brake
wear due to the light braking.
The vehicle will automatically exit the mode
if the brakes get too hot. Terrain Mode can
be turned back on after the brakes have
cooled.
When Terrain Mode is selected:
.Auto Engine Start/Stop will be disabled.
.The Terrain Mode indicator displays on
the instrument cluster.
Limited-Slip Differential
If equipped, the limited-slip differential can
give more traction on snow, mud, ice, sand,
or gravel. It works like a standard axle most
of the time, but when traction is low, this
feature allows the drive wheel with the
most traction to move the vehicle. For
vehicles with the limited-slip differential, driven under severe conditions, the rear axle
fluid should be changed. See
Maintenance
Schedule 0409.
Locking Rear Axle
Vehicles with a locking rear axle can give
more traction on snow, mud, ice, sand,
or gravel. It works like a standard axle most
of the time, but when traction is low, this
feature will allow the rear wheel with the
most traction to move the vehicle.
Cruise Control
{
Warning
Cruise control can be dangerous where
you cannot drive safely at a steady
speed. Do not use cruise control on
winding roads or in heavy traffic.
Cruise control can be dangerous on
slippery roads. On such roads, fast
changes in tire traction can cause
excessive wheel slip, and you could lose
control. Do not use cruise control on
slippery roads. If equipped with cruise control, a speed of
about 40 km/h (25 mph) or more can be
maintained without keeping your foot on
the accelerator. Cruise control does not work
at speeds below about 40 km/h (25 mph).
If the cruise control is being used and the
Traction Control System (TCS) or StabiliTrak/
Electronic Stability Control (ESC) begins to
limit wheel spin, the cruise control will
automatically disengage. See
Traction
Control/Electronic Stability Control 0248.
If a collision alert occurs when cruise control
is activated, cruise control is disengaged. See
Forward Collision Alert (FCA) System 0275.
When road conditions allow you to safely
use it again, cruise control can be turned
back on.
Turning off the TCS or StabiliTrak/ESC
system will disengage the cruise control.
If the brakes are applied, cruise control
disengages.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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Driving and Operating 257
{Warning
ACC will not detect or brake for children,
pedestrians, animals, or other objects.
Do not use ACC when:
.On winding and hilly roads or when
the camera sensor is blocked by snow,
ice, or dirt. The system may not
detect a vehicle ahead. Keep the
windshield and headlamps clean.
.When visibility is poor due to rain,
snow, fog, dirt, insect residue, or dust;
when other foreign objects obscure
the camera’s view; or when the
vehicle in front or oncoming traffic
causes additional environmental
obstructions, such as road spray. ACC
performance is limited under these
conditions.
.On slippery roads where fast changes
in tire traction can cause excessive
wheel slip
.With extremely heavy cargo loaded in
the cargo area or rear seat
.When towing a trailer
J:Press to turn the system on or off. The
indicator turns white on the instrument
cluster when ACC is turned on.
RES+ : Press briefly to resume the previous
set speed or to increase vehicle speed if ACC
is already activated. To increase speed by
about 1 km/h (1 mph), press RES+ briefly. To
increase speed to the next 5 km/h (5 mph)
mark on the speedometer, hold RES+.
SET– :Press briefly to set the speed and
activate ACC or to decrease vehicle speed if
ACC is already activated. To decrease speed
by about 1 km/h (1 mph), press SET– briefly.
To decrease speed to the next 5 km/h
(5 mph) mark on the speedometer,
hold SET–.
*: Press to disengage ACC without erasing
the selected set speed.
[: Press to select a following gap setting
for ACC of Far, Medium, or Near.
The speedometer reading can be displayed
in either English or metric units. See
Instrument Cluster 0106. The increment
value used depends on the units displayed.
Switching Between ACC and Regular Cruise
Control
To switch between ACC and regular cruise
control, press and hold
*. A Driver
Information Display (DIC) message displays.
See Vehicle Messages 0130.
ACC IndicatorRegular Cruise Control
Indicator
When ACC is engaged, a green
oindicator
will be lit on the instrument cluster and the
following gap will be displayed. When the

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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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./
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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./
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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.

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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.