tow GMC SIERRA 2021 Owner's Guide

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
116 Instruments and Controls
Caution
If the vehicle is driven continually with
this light on, the emission control system
may not work as well, the fuel economy
may be lower, and the vehicle may not
run smoothly. This could lead to costly
repairs that might not be covered by the
vehicle warranty.
Caution
Modifications to the engine, transmission,
exhaust, intake, or fuel system, or the
use of replacement tires that do not
meet the original tire specifications, can
cause this light to come on. This could
lead to costly repairs not covered by the
vehicle warranty. This could also affect
the vehicle’s ability to pass an Emissions
Inspection/Maintenance test. See
Accessories and Modifications0323.
If the light is flashing : A malfunction has
been detected that could damage the
emission control system and increase vehicle
emissions. Diagnosis and service may be
required. To help prevent damage, reduce vehicle
speed and avoid hard accelerations and
uphill grades. If towing a trailer, reduce the
amount of cargo being hauled as soon as
possible.
If the light continues to flash, find a safe
place to park. Turn the vehicle off and wait
at least 10 seconds before restarting the
engine. If the light is still flashing, follow
the previous guidelines and see your dealer
for service as soon as possible.
If the light is on steady :
A malfunction has
been detected. Diagnosis and service may be
required.
Check the following:
.If fuel has been added to the vehicle
using the capless funnel adapter, make
sure that it has been removed. See
“Filling the Tank with a Portable
Gas Can” underFilling the Tank (Pickup
Model) 0285 or
Filling the Tank (Chassis Cab Model) 0287. The diagnostic system can
detect if the adapter has been left
installed in the vehicle, allowing fuel to
evaporate into the atmosphere. A few
driving trips with the adapter removed
may turn off the light.
.Poor fuel quality can cause inefficient
engine operation and poor driveability,
which may go away once the engine is
warmed up. If this occurs, change the fuel
brand. It may require at least one full
tank of the proper fuel to turn the light
off. See Recommended Fuel (Except 6.2L
V8 Engine) 0283 or
Recommended Fuel (6.2L V8 Engine)
0 284.
If the light remains on, see your dealer.
Emissions Inspection and Maintenance
Programs
If the vehicle requires an Emissions
Inspection/Maintenance test, the test
equipment will likely connect to the
vehicle's Data Link Connector (DLC).
The DLC is under the instrument panel to
the left of the steering wheel. Connecting
devices that are not used to perform an
Emissions Inspection/Maintenance test or to

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Instruments and Controls 117
service the vehicle may affect vehicle
operation. SeeAdd-On Electrical Equipment
0 318. See your dealer if assistance is
needed.
The vehicle may not pass inspection if:
.The light is on when the engine is
running.
.The light does not come on when the
ignition is on while the engine is off.
.Critical emission control systems have not
been completely diagnosed. If this
happens, the vehicle would not be ready
for inspection and might require
several days of routine driving before the
system is ready for inspection. This can
happen if the 12-volt battery has recently
been replaced or run down, or if the
vehicle has been recently serviced.
See your dealer if the vehicle will not pass
or cannot be made ready for the test.
Brake System Warning Light
MetricEnglish
This light should come on briefly when the
vehicle is turned on. If it does not come on
then, have it fixed so it will be ready to
warn you if there is a problem.
If the light comes on and stays on at start
up, there is a brake problem. Have the brake
system inspected right away.
If the light comes on while driving, pull off
the road and stop carefully. If equipped with
electric brake boost, vehicle speed may be
limited when the brake system warning
light comes on. The brake pedal might be
harder to push, or the brake pedal may go
closer to the floor. It could take longer to
stop. If the light is still on, have the vehicle
towed for service. See Towing the Vehicle
0 394.
{Warning
The brake system might not be working
properly if the brake system warning
light is on. Driving with the brake system
warning light on can lead to a crash.
If the light is still on after the vehicle has
been pulled off the road and carefully
stopped, have the vehicle towed for
service.
Electric Parking Brake Light
MetricEnglish
This light comes on when the parking brake
is applied. If the light continues flashing
after the parking brake is released, or while
driving, there is a problem with the Electric
Parking Brake system. A message may also
display in the Driver Information
Center (DIC).
If the light does not come on, or remains
flashing, see your dealer.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Instruments and Controls 119
Tow/Haul Mode Light
For vehicles with the Tow/Haul Mode
feature, this light comes on when the Tow/
Haul Mode has been activated.
SeeTow/Haul Mode 0242.
Hill Descent Control Light
If equipped, the Hill Descent Control light
comes on when the system is ready for use.
When the light flashes, the system is active.
See Hill Descent Control (HDC) 0250.
Lane Keep Assist (LKA) Light
After the vehicle is started, this light turns
off and stays off if LKA has not been turned
on or is unavailable.
If equipped, this light is white if LKA is
turned on, but not ready to assist. This light
is green if LKA is turned on and is ready to
assist.
LKA may assist by gently turning the
steering wheel if the vehicle approaches a
detected lane marking. The LKA light is
amber when assisting.
This light flashes amber as a Lane Departure
Warning (LDW) alert, to indicate that the
lane marking has been crossed.
LKA will not assist or alert if the turn signal
is active in the direction of lane departure,
or if LKA detects that you are accelerating,
braking, or actively steering.
See Lane Keep Assist (LKA) 0281.
Vehicle Ahead Indicator
If equipped, this indicator will display green
when a vehicle is detected ahead and amber
when you are following a vehicle ahead
much too closely.
See Forward Collision Alert (FCA) System
0 275.
Pedestrian Ahead Indicator
If equipped, this indicator will display amber
when a nearby pedestrian is detected in
front of the vehicle.
See Front Pedestrian Braking (FPB) System
0 278.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
128 Instruments and Controls
Head-Up Display (HUD)
{Warning
If the HUD image is too bright or too
high in your field of view, it may take
you more time to see things you need to
see when it is dark outside. Be sure to
keep the HUD image dim and placed low
in your field of view.
If equipped with HUD, some information
about the operation of the vehicle is
projected onto the windshield. The image is
projected through the HUD lens on top of
the instrument panel. The information
appears as an image focused out toward the
front of the vehicle.
Caution
If you try to use the HUD image as a
parking aid, you may misjudge the
distance and damage your vehicle. Do not
use the HUD image as a parking aid.
The HUD information can be displayed in
various languages. The speedometer reading
and other numerical values can be displayed
in either English or metric units. The language selection is changed through
the radio, and the units of measurement is
changed through the instrument cluster. See
Settings
0186 and “Options” under
Instrument Cluster 0106.
HUD Display on the Windshield
Depending on how the vehicle is equipped,
the HUD may display some of the following
vehicle information and vehicle messages or
alerts:
.Speed
.Audio
.Phone
.Navigation
.Driver Assistance Features
.Vehicle Messages Some vehicle messages or alerts displayed in
the HUD may be cleared by using the
steering wheel controls.
The HUD control is to the left of the
steering wheel.
To adjust the HUD image:
1. Adjust the driver seat.
2. Start the engine.
3. Use the following settings to adjust the HUD.
$:Press or pull to center the HUD image.
The HUD image can only be adjusted up and
down, not side to side.
!: Press to select the display view. Each
press will change the display view.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
132 Instruments and Controls
Touch Off or On.
Auto Rear Defog
This setting automatically turns the rear
defogger on based on temperature and
humidity conditions.
Touch Off or On.
Collision/Detection Systems
Touch and the following may display:
.Alert Type
.Forward Collision System
.Front Pedestrian Detection
.Adaptive Cruise Go Notifier
.Lane Change Alert
.Park Assist
.Rear Camera Park Assist Symbols
.Rear Cross Traffic Alert
Alert Type
This feature sets the type of alert from the
driver assistance systems to help avoid
crashes.
Touch Beeps or Safety Alert Seat. Forward Collision System
This setting can alert of a potential crash
with a detected vehicle ahead and can apply
brakes to help reduce a collision’s severity.
Touch Off, Alert, or Alert and Brake.
Front Pedestrian Detection
This feature may help avoid or reduce the
harm caused by front-end crashes with
nearby pedestrians. See
Front Pedestrian
Braking (FPB) System 0278.
Touch Off, Alert, or Alert and Brake.
Adaptive Cruise Go Notifier
This setting determines if an alert will
appear when Adaptive Cruise Control brings
the vehicle to a complete stop and the
vehicle ahead of you starts moving again.
See Adaptive Cruise Control (Camera) 0256.
Touch Off or On.
Lane Change Alert
This allows the feature to be turned on or
off. See Lane Change Alert (LCA) 0280.
Touch Off or On. Park Assist
This allows the feature to be turned on or
off. See
Assistance Systems for Parking or
Backing 0266.
Select Off, On, or On with Towbar.
Rear Camera Park Assist Symbols
This setting enables the Rear Camera Park
Assist Symbols. See Assistance Systems for
Parking or Backing 0266.
Touch Off or On.
Rear Cross Traffic Alert
This allows the Rear Cross Traffic Alert
feature to be turned on or off. See
Assistance Systems for Parking or Backing
0 266.
Touch Off or On.
Comfort and Convenience
Touch and the following may display:
.Chime Volume
.Reverse Tilt Mirror
.Remote Mirror Folding
Chime Volume
This determines the chime volume level.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/6/20
Lighting 141
.The vehicle is loaded such that the front
end points upward, causing the light
sensor to aim high and not detect
headlamps and taillamps.
.Driving on winding or hilly roads.
The automatic high-beam headlamps may
need to be disabled if any of the above
conditions exist.
Exterior Lamps Off Reminder
A reminder chime sounds when the
headlamps or parking lamps are manually
turned on, the ignition is off, and a door is
open. To disable the chime, turn the
lamps off.
Headlamp High/Low-Beam
Changer
Push the turn signal lever toward the
instrument panel to change the headlamps
from low to high beam.
Pull or push the turn signal lever to return
to low-beam headlamps.
When the high-beam headlamps are on, this
indicator light on the instrument cluster will
also be on.
Flash-to-Pass
This feature lets you use the high-beam
headlamps to signal a driver in front of you
that you want to pass. It works even if the
headlamps are in the automatic position.
To use it, pull the turn signal lever toward
you, then release it.
If the headlamps are in the automatic
position or on low beam, the high-beam
headlamps will turn on. Depending on the
type of headlamp, they will either turn off
after a short duration or stay on as long as
you hold the lever toward you. The
high-beam indicator on the instrument
cluster will come on. Release the lever to
return to normal operation.
Daytime Running Lamps (DRL)
DRL can make it easier for others to see the
front of the vehicle during the day. Fully
functional DRL are required on all vehicles
first sold in Canada.
The DRL system comes on when the
following conditions are met:
.The ignition is on.
.The exterior lamp control is in AUTO.
.The transmission is not in P (Park).
.The light sensor determines it is daytime.
When the DRL system is on, only the DRL
are on. The taillamps, sidemarker lamps,
instrument panel lights, and other lamps
will not be on.
When it begins to get dark, the automatic
headlamp system switches from DRL to the
headlamps.
To turn off the DRL, turn the exterior lamp
control to
Oand then release. For vehicles
first sold in Canada, off will only work when
the vehicle is parked.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/6/20
Lighting 143
Turn and Lane-Change Signals
An arrow on the instrument cluster flashes
in the direction of the turn or lane change.
Move the turn signal lever all the way up or
down to signal a turn.
Partially raise or lower the lever for less
than one second until the arrow starts to
flash to signal a lane change. This causes
the turn signals to automatically flash three
times. It will flash six times if Tow/Haul
Mode is active. Holding the turn signal lever
for more than one second will cause the
turn signals to flash until the lever is
released.The lever returns to its starting position
whenever it is released.
If after signaling a turn or a lane change the
arrows flash rapidly or do not come on, a
signal bulb could be burned out. If equipped
with LED turn signals, see your dealer.
Replace any burned out bulbs. If a bulb is
not burned out, check the fuse. See
Fuses
and Circuit Breakers 0353.
Turn Signal On Chime
If the turn signal is left on for more than
1.2 km (0.75 mi), a chime sounds at each
flash of the turn signal. A message may
appear in the Driver Information Center
(DIC). See Vehicle Messages 0130. To turn
the chime and message off, move the turn
signal lever to the off position.
Fog Lamps
If equipped, the fog lamp control is near the
exterior lamp control to the left of the
steering column.
The ignition must be on for the fog lamps
to come on.
#: Press to turn the fog lamps on or off.
A light will come on in the instrument
cluster.
When the fog lamps are turned on, the
parking lamps automatically turn on.
When the headlamps are changed to high
beam, the fog lamps also go off. When the
high-beam headlamps are turned off, the fog
lamps will come on again.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Infotainment System 151
.When the power is on and the
system is not muted, a quick
status pane will display when
Ois
pressed. Pressing
Owill mute the
system and trigger this pane to
show a long press is required to
actually power down the system.
.Turn to decrease or increase the
volume.
4.6
.Radio: Press and release to go to
the next station or channel. Press
and hold to fast seek the next
strongest station or channel.
.USB/Bluetooth: Press to seek the
next track. Press and hold to fast
forward through a track. Release to
return to playing speed. See USB
Port 0158 or
Bluetooth Audio 0162.
5.v
.Press and release to access the
phone display or answer an
incoming call. Home Page
The Home Page is where vehicle application
icons are accessed. Some applications are
disabled when the vehicle is moving.
The Home Page can be set up to have up to
four pages with eight icons per page.
Swipe left or right across the display to
access the pages of icons.
Managing Home Page Icons
1. Touch and hold any of the Home Page icons to enter edit mode.
2. Continue holding the icon and drag it to the desired position.
3. Release your finger to drop the icon in the desired position.
4. To move an application to another page, drag the icon to the edge of the display
toward the desired page.
5. Continue dragging and dropping application icons as desired.
Steering Wheel Controls
If equipped, some audio controls can be
adjusted at the steering wheel.
g:Press to answer an incoming call or
start voice recognition. See Bluetooth
(Pairing and Using a Phone) 0181 or
Bluetooth (Overview) 0180.
c:Press to decline an incoming call or
end a current call. Press to mute or unmute
the infotainment system when not on a call.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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Infotainment System 157
seconds. The radio will also display
icons representing additional channels
(HD2, ...HD8), that may be available.
When the radio successfully tunes to a
HD station, the HD logo will display and
digital audio will play.
2. Touch the display arrows to tune to the previous or next HD Radio station.
There may be a delay before the station
starts playing.
The HD Radio station number is indicated
next to the HD logo.
HD Radio stations can be saved as favorites.
For a list of all stations, see
www.hdradio.com.
HD Radio Troubleshooting
Digital Audio Delay : Wait for the signal to
process. This can take several seconds.
Volume Change, Audio Skip, Echo, Digital
Audio Lost : Station signal strength may be
weak, the station is out of range, or the
station may be out of alignment. Verify
proper reception on another station.
If the HD Radio signal weakens while
listening to HD1, the radio will automatically
switch to the analog version of the radio
station. If the HD Radio signal loses reception while
listening to stations HD2 to HD8, the radio
mutes until the signal can be recovered or
until the station is changed.
HD Radio can be disabled if driving in a
weak signal area. Touch HD Radio On/Off to
toggle HD Radio reception on and off.
Radio Data System (RDS)
If equipped, RDS features are available for
use only on FM stations that broadcast RDS
information. With RDS, the radio can:
.Group stations by Category (i.e., Program
Type) such as Rock, Jazz, Classical, etc.
.Display messages from radio stations.
This system relies on receiving specific
information from these stations and only
works when the information is available.
It is possible that a radio station could
broadcast incorrect information that causes
the radio features to work improperly. If this
happens, contact the radio station.
When information is broadcast from a RDS
station, the station name or call letters
display on the audio screen. Radio text
supporting the currently playing broadcast
may also appear.
Satellite Radio
SiriusXM Radio Service
If equipped, vehicles with a valid SiriusXM
radio subscription can receive SiriusXM
programming.
SiriusXM radio has a wide variety of
programming and commercial-free music,
coast to coast, in digital-quality sound. In
the U.S., see www.siriusxm.com or call
1-888-601-6296. In Canada, see
www.siriusxm.ca or call 1-877-438-9677.
When SiriusXM is active, the channel name,
number, song title, and artist appear on the
display.
SiriusXM with 360L
SiriusXM with 360L interface has enhanced
in-vehicle listening experience for
subscribers. The experience now offers more
categories and system learned
recommendations toward discovering more
personalized content.
To use the full SiriusXM 360L program,
including streaming content and listening
recommendations, OnStar Connected Access
is required. Connected vehicle services vary

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
194 Infotainment System
Manage Settings
Audio Volume Limit :Allows the audio
volume limit to be turned on or off. Touch
Set Audio Volume Limit to choose the
maximum allowable audio volume level.
Set Audio Volume Limit : Allows a
maximum radio volume to be set. Use the
arrows to choose the maximum allowable
level for the audio volume.
Teen Driver Speed Limiter : Limits the
maximum speed of the vehicle. When the
speed limiter is turned on and the vehicle is
started with a Teen Driver key, the DIC
displays a message that the top speed is
limited.
On certain vehicles, when the Speed Limiter
is turned ON, the vehicle’s maximum
acceleration will be limited. The DIC will
display a message that the acceleration is
limited.
Teen Driver Speed Warning : Allows the
speed warning to be turned on or off. Touch
Set Teen Driver Speed Warning to set the
warning speed. Set Teen Driver Speed Warning :
Displays a
warning in the DIC when exceeding a
selectable speed. Choose the desired speed
warning level. The speed warning does not
limit the speed of the vehicle.
SiriusXM Explicit Content Filter (if
equipped) : Allows the SiriusXM Explicit
Content Filter to be turned ON or OFF.
When ON, the teen driver will not be able
to listen to SiriusXM stations that contain
explicit content, and the Explicit Content
Filter selection in the Audio Settings will be
unavailable for change.
When Teen Driver is Active:
.If equipped with Buckle to Drive, shifting
out of P (Park) will be prevented if the
driver seat belt, and in some vehicles the
front passenger seat belt, is not buckled.
.The radio will mute when the driver seat
belt, and in some vehicles the front
passenger seat belt, is not buckled. The
audio from any device paired to the
vehicle will also be muted.
.An object placed on the front passenger
seat, such as a briefcase, handbag,
grocery bag, laptop, or other electronic
device, could cause the passenger sensing
system to falsely sense an unbuckled
front passenger and mute the radio. If this happens, remove the object from
the seat. See
Passenger Sensing System
0 66.
.Some safety systems, such as Forward
Collision Alert, if equipped, cannot be
turned off.
.The gap setting for the Forward Collision
Alert and Adaptive Cruise Control,
if equipped, cannot be changed.
.When trying to change a safety feature
that is not configurable in Teen Driver,
the DIC displays a message indicating
that Teen Driver is active and the action
is not available.
.Super Cruise, if equipped, is not available.
.Enhanced Low Fuel Warning (if equipped)
–When the vehicle is low on fuel, the
low fuel light on the instrument cluster
flashes and the DIC low fuel warning
cannot be dismissed.
.Do not tow a trailer.
Report Card
The vehicle owner must secure the driver’s
consent to record certain vehicle data when
the vehicle is driven with a registered Teen
Driver key. There is one Report Card per