2021 GMC SIERRA Side mirror operation

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
276 Driving and Operating
Without Head-Up Display
When your vehicle approaches another
detected vehicle too rapidly, the red FCA
display will flash on the windshield. Also,
eight rapid high-pitched beeps will sound
from the front, or both sides of the Safety
Alert Seat will pulse five times. When this
Collision Alert occurs, the brake system may
prepare for driver braking to occur more
rapidly which can cause a brief, mild
deceleration. Continue to apply the brake
pedal as needed. Cruise control may be
disengaged when the Collision Alert occurs.
Tailgating Alert
The vehicle ahead indicator will display
amber when you are following a vehicle
ahead much too closely.
Selecting the Alert Timing
The Collision Alert control is on the steering
wheel. Press
[to set the FCA timing to
Far, Medium, or Near. The first button press
shows the current setting on the DIC.
Additional button presses will change this
setting. The chosen setting will remain until
it is changed and will affect the timing of
both the Collision Alert and the Tailgating
Alert features. The timing of both alerts will
vary based on vehicle speed. The faster the
vehicle speed, the farther away the alert will
occur. Consider traffic and weather
conditions when selecting the alert timing.
The range of selectable alert timings may
not be appropriate for all drivers and driving
conditions.
If your vehicle is equipped with Adaptive
Cruise Control (ACC), changing the FCA
timing setting automatically changes the
following gap setting (Far, Medium,
or Near).
Following Distance Indicator
The following distance to a moving vehicle
ahead in your path is indicated in following
time in seconds on the Driver Information
Center (DIC). The minimum following time is
0.5 seconds away. If there is no vehicle
detected ahead, or the vehicle ahead is out
of sensor range, dashes will be displayed.
Unnecessary Alerts
FCA may provide unnecessary alerts for
turning vehicles, vehicles in other lanes,
objects that are not vehicles, or shadows.
These alerts are normal operation and the
vehicle does not need service.
Cleaning the System
If the FCA system does not seem to operate
properly, this may correct the issue:
.Clean the outside of the windshield in
front of the rearview mirror.
.Clean the entire front of the vehicle.
.Clean the headlamps.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 281
When the vehicle is started, both outside
mirror LCA displays will briefly come on to
indicate the system is operating. When the
vehicle is in a forward gear, the left or right
side mirror display will light up if a moving
vehicle is detected in the next lane over in
that blind zone or rapidly approaching that
zone. If the turn signal is activated in the
same direction as a detected vehicle, this
display will flash as an extra warning not to
change lanes.
LCA can be disabled through vehicle
personalization. When you disable LCA, SBZA
is also disabled. SeeVehicle Personalization
0 131. If LCA is disabled by the driver, the
LCA mirror displays will not light up.
When the System Does Not Seem to
Work Properly
The LCA system requires some driving for
the system to calibrate to maximum
performance. This calibration may occur
more quickly if the vehicle is driving on a
straight highway road with traffic and
roadside objects (e.g., guardrails, barriers).
LCA displays may not come on when
passing a vehicle quickly, for a stopped
vehicle, or when towing a trailer. The LCA
detection zones that extend back from the side of the vehicle do not move further back
when a trailer is towed. Use caution while
changing lanes when towing a trailer. LCA
may alert to objects attached to the vehicle,
such as a trailer, bicycle, or object extending
out to either side of the vehicle. Attached
objects may also interfere with the
detection of vehicles. This is normal system
operation; the vehicle does not need service.
LCA may not always alert the driver to
vehicles in the next lane over, especially in
wet conditions or when driving on sharp
curves. The system does not need to be
serviced. The system may light up due to
guardrails, signs, trees, shrubs, and other
non-moving objects. This is normal system
operation; the vehicle does not need service.
LCA may not operate when the LCA sensors
in the left or right corners of the rear
bumper are covered with mud, dirt, snow,
ice, or slush, or in heavy rainstorms. For
cleaning instructions, see "Washing the
Vehicle" under
Exterior Care0398. If the
DIC still displays the system unavailable
message after cleaning both sides of the
vehicle toward the rear corners of the
vehicle, see your dealer. If the LCA displays do not light up when
moving vehicles are in the side blind zone or
are rapidly approaching this zone and the
system is clean, the system may need
service. Take the vehicle to your dealer.
Radio Frequency Information
See
Radio Frequency Statement 0436.
Lane Keep Assist (LKA)
If equipped, LKA may help avoid crashes due
to unintentional lane departures. This
system uses a camera to detect lane
markings between 60 km/h (37 mph) and
180 km/h (112 mph). It may assist by gently
turning the steering wheel if the vehicle
approaches a detected lane marking. It may
also provide a Lane Departure Warning
(LDW) alert if the vehicle crosses a detected
lane marking. LKA can be overridden by
turning the steering wheel. This system is
not intended to keep the vehicle centered in
the lane. LKA will not assist and alert if the
turn signal is active in the direction of lane
departure, or if it detects that you are
accelerating, braking or actively steering.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 283
When the System Does Not Seem to
Work Properly
The system performance may be
affected by:
.Close vehicles ahead.
.Sudden lighting changes, such as when
driving through tunnels.
.Banked roads.
.Roads with poor lane markings, such as
two-lane roads.
If the LKA system is not functioning
properly when lane markings are clearly
visible, cleaning the windshield may help.
A camera blocked message may display if
the camera is blocked. Some driver
assistance systems may have reduced
performance or not work at all. An LKA or
LDW unavailable message may display if the
systems are temporarily unavailable. This
message could be due to a blocked camera.
The LKA system does not need service. Clean
the outside of the windshield behind the
rearview mirror.
LKA assistance and/or LDW alerts may occur
due to tar marks, shadows, cracks in the
road, temporary or construction lane
markings, or other road imperfections. This is normal system operation; the vehicle does
not need service. Turn LKA off if these
conditions continue.
Fuel
Top Tier Fuel
GM recommends the use of TOP TIER
Detergent Gasoline to keep the engine clean,
reduce engine deposits, and maintain
optimal vehicle performance. Look for the
TOP TIER Logo or see www.toptiergas.com
for a list of TOP TIER Detergent Gasoline
marketers and applicable countries.
Recommended Fuel (Except 6.2L
V8 Engine)
For diesel engine vehicles, see
“Fuel for
Diesel Engines” in the Duramax diesel
supplement.
If the vehicle has a yellow fuel cap or a
yellow sticker on the fuel door, E85 or
FlexFuel can be used. If the vehicle does not
have a yellow fuel cap or yellow sticker, do
not use gasoline with ethanol levels greater
than 15% by volume. See E85 or FlexFuel
0 284.
Use regular unleaded gasoline meeting
ASTM specification D4814 with a posted
octane rating of 87 —(R+M)/2 —or higher.
Do not use gasoline with a posted octane
rating of less than 87, as this may cause
engine knock and will lower fuel economy.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
318 Driving and Operating
If Tow/Haul Mode is off and this setting is
on for a Trailer Profile, each time the
ignition is turned on a reminder will appear
to turn on Tow/Haul Mode when the Trailer
Profile is active.
If Tow/Haul Mode is on and this setting is
on for a Trailer Profile, the reminder will not
appear when the Trailer Profile is active.
Trailer Length Indicator
Touch Trailer Length Indicator to view the
Trailer Length Indicator settings page. If this
setting is ON a guideline is displayed in the
side mirror camera view to indicate the rear
of the attached trailer. If this setting is OFF
the guideline will not be displayed.
This setting will default to OFF if the trailer
length indicator feature is not set up. See
"Towing Assistance" for details on the setup.
Conversions and Add-Ons
Add-On Electrical Equipment
{Warning
The Data Link Connector (DLC) is used for
vehicle service and Emission Inspection/
Maintenance testing. SeeMalfunction
Indicator Lamp (Check Engine Light) 0115.
A device connected to the DLC —such as
an aftermarket fleet or driver-behavior
tracking device —may interfere with
vehicle systems. This could affect vehicle
operation and cause a crash. Such devices
may also access information stored in the
vehicle’s systems.
Caution
Some electrical equipment can damage
the vehicle or cause components to not
work and would not be covered by the
vehicle warranty. Always check with your
dealer before adding electrical equipment.
Add-on equipment can drain the vehicle's
12-volt battery, even if the vehicle is not
operating. The vehicle has an airbag system. Before
attempting to add anything electrical to the
vehicle, see
Servicing the Airbag-Equipped
Vehicle 069 and
Adding Equipment to the Airbag-Equipped
Vehicle 069.
For information on wiring auxiliary switches,
see www.gmupfitter.com or contact your
dealer.
Adding a Snow Plow or Similar
Equipment
Caution
Do not exceed 72 km/h (45 mph) with a
snow plow mounted to the vehicle. The
vehicle could overheat and be damaged.
Before installing a snow plow on the vehicle,
follow these guidelines:
Caution
If the vehicle does not have the snow
plow prep package, RPO VYU, adding a
plow can damage the vehicle, and the
repairs would not be covered by the
vehicle warranty. Unless the vehicle was
built to carry a snow plow, do not add
(Continued)

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./Cana-
da/Mexico-14632426) - 2021 - CRC - 11/5/20
458 Index
Storage Compartments . . . . . . . . . . . . . . . . . . . 95
StrutsGas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
Stuck Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
Sun Visors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Sunroof . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
System Brake Pad Life . . . . . . . . . . . . . . . . . . . . . . . . . 342
Engine Air Filter Life . . . . . . . . . . . . . . . . . . . 333
Forward Collision Alert (FCA) . . . . . . . . . . . 275
Global Positioning . . . . . . . . . . . . . . . . . . . . . . 173
Infotainment . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
OnStar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
Systems
Driver Assistance . . . . . . . . . . . . . . . . . . . . . . 265
T
Tachometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
Tailgate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
TaillampsBulb Replacement . . . . . . . . . . . . . . . . . . . . . . 351
Task Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
Teen Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
Text Telephone (TTY) Users . . . . . . . . . . . . . . 430
Theft-Deterrent Systems . . . . . . . . . . . . . . . . . . .32 Immobilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Tires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360
All-Season . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
All-Terrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
Buying New Tires . . . . . . . . . . . . . . . . . . . . . . 376
Chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
Changing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381
Designations . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
Different Size . . . . . . . . . . . . . . . . . . . . . . . . . . 377
Full-Size Spare . . . . . . . . . . . . . . . . . . . . . . . . . 390
If a Tire Goes Flat . . . . . . . . . . . . . . . . . . . . . 380
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
Pressure Light . . . . . . . . . . . . . . . . . . . . . . . . . 122
Pressure Monitor Operation . . . . . . . . . . . 369
Pressure Monitor System . . . . . . . . . . . . . . 368
Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
Sidewall Labeling . . . . . . . . . . . . . . . . . . . . . . 362
Terminology and Definitions . . . . . . . . . . . 365
Uniform Tire Quality Grading . . . . . . . . . . 377
Wheel Alignment and Tire Balance . . . . 378
Wheel Replacement . . . . . . . . . . . . . . . . . . . . 378
When It Is Time for New Tires . . . . . . . . . 375
Winter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
Top Tier Fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
Tow/Haul Mode . . . . . . . . . . . . . . . . . . . . . . . . . 242
Tow/Haul Mode Light . . . . . . . . . . . . . . . . . . . . 119 Towing
Driving Characteristics . . . . . . . . . . . . . . . . . 288
Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
General Information . . . . . . . . . . . . . . . . . . . 288
Recreational Vehicle . . . . . . . . . . . . . . . . . . . 395
Trailer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
Trailer Sway Control (TSC) . . . . . . . . . . . . . 306
Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394
Traction Limited-Slip Differential . . . . . . . . . . . . . . . . 254
Off Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
Traction Control/Electronic Stability Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
Trademarks and License Agreements . . . . . 195
Trailer Sway Control (TSC) . . . . . . . . . . . . . . . . . . . . 306
Tow Mirrors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Towing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
Trailer Towing App . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
Trailering App . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
Transfer Case . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
Transmission
Automatic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
Fluid, Automatic . . . . . . . . . . . . . . . . . . . . . . . 333
Transportation Program, Courtesy . . . . . . . 433
Trip Odometer . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
Truck-Camper Loading Information . . . . . . . 226