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
386 Vehicle Care
8. Remove any rust or dirt from the wheelbolts, mounting surfaces, and spare
wheel.
9. Install the spare tire.
{Warning
Never use oil or grease on bolts or nuts
because the nuts might come loose. The
vehicle's wheel could fall off, causing a
crash.
10. Put the wheel nuts back on with the rounded end of the nuts toward the
wheel. 11. Tighten each wheel nut by hand. Then
use the wheel wrench to tighten the
nuts until the wheel is held against
the hub.
12. Turn the wheel wrench counterclockwise to lower the vehicle. Lower the jack
completely.
{Warning
If wheel studs are damaged, they can
break. If all the studs on a wheel broke,
the wheel could come off and cause a
crash. If any stud is damaged because of
a loose-running wheel, it could be that all
of the studs are damaged. To be sure,
replace all studs on the wheel. If the stud
holes in a wheel have become larger, the
wheel could collapse in operation. Replace
any wheel if its stud holes have become
larger or distorted in any way. Inspect
hubs and hub‐piloted wheels for damage.
Because of loose running wheels, piloting
pad damage may occur and require
replacement of the entire hub, for proper
centering of the wheels. When replacing
studs, hubs, wheel nuts or wheels, be
sure to use GM original equipment parts.
{Warning
Wheel nuts that are improperly or
incorrectly tightened can cause the
wheels to become loose or come off. The
wheel nuts should be tightened with a
torque wrench to the proper torque
specification after replacing. Follow the
torque specification supplied by the
aftermarket manufacturer when using
accessory locking wheel nuts. See
Capacities and Specifications 0424 for
original equipment wheel nut torque
specifications.
Caution
Improperly tightened wheel nuts can lead
to brake pulsation and rotor damage. To
avoid expensive brake repairs, evenly
tighten the wheel nuts in the proper
sequence and to the proper torque
specification. See Capacities and
Specifications 0424 for the wheel nut
torque specification.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Vehicle Care 387
13. Tighten the nuts firmly in a crisscrosssequence, as shown, by turning the
wheel wrench clockwise.
When reinstalling the regular wheel and tire,
also reinstall either the center cap,
or bolt-on hub cap, depending on what the
vehicle is equipped with. For center caps,
place the cap on the wheel and tap it into
place until it seats flush with the wheel. The
cap only goes on one way. Be sure to line
up the tab on the center cap with the
indentation on the wheel. For bolt-on hub
caps, align the plastic nut caps with the
wheel nuts and then tighten by hand. Then
use the wheel wrench to tighten.
Storing a Flat or Spare Tire and Tools
{Warning
Storing a jack, a tire, or other equipment
in the passenger compartment of the
vehicle could cause injury. In a sudden
stop or collision, loose equipment could
strike someone. Store all these in the
proper place.
{Warning
Failure to follow these tire storage
instructions carefully could result in
personal injury or property damage if the
hoist cable fails or if the tire comes loose.
Make sure the tire is stored securely
before driving.
Caution
Storing an aluminum wheel with a flat
tire under your vehicle for an extended
period of time or with the valve stem
pointing up can damage the wheel.
Always stow the wheel with the valve
stem pointing down and have the wheel/
tire repaired as soon as possible.
Caution
The tire hoist can be damaged if there is
no tension on the cable when using it. To
have the necessary tension, the spare or
road tire and wheel assembly must be
installed on the tire hoist to use it.
{Warning
An improperly stored spare tire could
come loose and cause a crash. To avoid
personal injury or property damage,
always store the spare tire when the
vehicle is parked on a level surface.
Store the tire under the rear of the vehicle
in the spare tire carrier.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Vehicle Care 391
Caution (Continued)
would not be covered by the warranty.
Never use four-wheel drive when a
different size spare tire is installed on the
vehicle.
The vehicle may have a different size spare
tire than the road tires originally installed
on the vehicle. This spare tire was developed
for use on this vehicle, so it is all right to
drive on it. If the vehicle has four-wheel
drive and a different size spare tire is
installed, drive only in two-wheel drive.
After installing the spare tire on the vehicle,
stop as soon as possible and check that the
spare is correctly inflated. The spare tire is
made to perform well at speeds up to
112 km/h (70 MPH) at the recommended
inflation pressure, so you can finish
your trip.
Have the damaged or flat road tire repaired
or replaced and installed back onto the
vehicle as soon as possible so the spare tire
will be available in case it is needed again.
Do not mix tires and wheels of difference
sizes, because they will not fit. Keep the
spare tire and its wheel together. If the vehicle has a spare tire that does not
match the original road tires and wheels in
size and type, do not include the spare in
the tire rotation.
Jump Starting
Jump Starting - North America
For more information about the vehicle
battery, see
Battery - North America 0343.
If the vehicle's battery (or batteries) has run
down, you may want to use another vehicle
and some jumper cables to start your
vehicle. Be sure to use the following steps
to do it safely.
{Warning
WARNING: Battery posts, terminals, and
related accessories contain lead and lead
compounds, chemicals known to the
State of California to cause cancer and
birth defects or other reproductive harm.
Batteries also contain other chemicals
known to the State of California to cause
cancer. WASH HANDS AFTER HANDLING.
(Continued)
Warning (Continued)
For more information go to
www.P65Warnings.ca.gov/
passenger-vehicle.
See California Proposition 65 Warning 0322
and the back cover.
{Warning
Batteries can hurt you. They can be
dangerous because:
.They contain acid that can burn you.
.They contain gas that can explode or
ignite.
.They contain enough electricity to
burn you.
If you do not follow these steps exactly,
some or all of these things can hurt you.
Caution
Ignoring these steps could result in costly
damage to the vehicle that would not be
covered by the vehicle warranty. Trying
(Continued)

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Vehicle Care 393
4. Turn the ignition off on both vehicles.Unplug unnecessary accessories plugged
into the accessory power outlets. Turn
off the radio and all the lamps that are
not needed. This will avoid sparks and
help save both batteries. And it could
save the radio!
5. Open the hood on the other vehicle and locate the positive (+) and negative (−)
terminal locations on that vehicle.
The positive (+) terminal is under a red
plastic cover at the positive battery post.
To uncover the positive (+) terminal,
open the red plastic cover.
For more information on the location of
the remote positive (+) and remote
negative (−) terminals, see Engine
Compartment Overview 0325.
{Warning
An electric fan can start up even when
the engine is not running and can injure
you. Keep hands, clothing, and tools
away from any underhood electric fan.
{Warning
Using a match near a battery can cause
battery gas to explode. People have been
hurt doing this, and some have been
blinded. Use a flashlight if you need
more light.
Battery fluid contains acid that can burn
you. Do not get it on you. If you
accidentally get it in your eyes or on
your skin, flush the place with water and
get medical help immediately.
{Warning
Fans or other moving engine parts can
injure you badly. Keep your hands away
from moving parts once the engine is
running.
6. Check that the jumper cables do not have loose or missing insulation. If they
do, you could get a shock. The vehicles
could be damaged too.
Before you connect the cables, here are
some basic things you should know.
Positive (+) will go to positive (+) or to a
remote positive (+) terminal if the vehicle has one. Negative (−) will go to a
heavy, unpainted metal engine part or to
a remote negative (−) terminal if the
vehicle has one.
Do not connect positive (+) to negative
(−) or you will get a short that would
damage the battery and maybe other
parts too. And do not connect the
negative (−) cable to the negative (−)
terminal on the dead battery because
this can cause sparks.
7. Connect one end of the red positive (+) cable to the remote positive (+) terminal
of the vehicle with the discharged
battery.
8. Do not let the other end touch metal. Connect it to the positive (+) terminal of
the good battery. Use a remote
positive (+) terminal if the vehicle
has one.
9. Connect one end of the black negative (−) cable to the negative (−) terminal of
the good battery. Use a remote negative
(−) terminal if the vehicle has one.
Do not let the other end touch anything
until the next step.
10. Connect the other end of the negative (−) cable to the remote negative (−)
terminal to the discharged battery.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
396 Vehicle Care
Dinghy Towing (Vehicles with a
Two-Speed Transfer Case)
Only dinghy tow four-wheel-drive vehicles
with a two-speed transfer case that have an
N (Neutral) and a 4
n(Four-Wheel Drive
Low) setting.
{Warning
Shifting a four-wheel-drive vehicle's
transfer case into N (Neutral) can allow
the vehicle to move even if the
transmission is in P (Park). You or others
could be injured. Set the parking brake
and use wheel blocks before shifting the
transfer case to N (Neutral). To dinghy tow:
1. Position the vehicle being towed behind the tow vehicle, facing forward and on a
level surface.
2. Securely attach the vehicle being towed to the tow vehicle.
3. Apply the parking brake and start the engine.
4. Shift the transfer case to N (Neutral). See “Shifting into N (Neutral)” under
Four-Wheel Drive 0242.
5. With the engine running, release the parking brake and verify that the
transfer case is in N (Neutral) by shifting
the transmission to D (Drive) and then to
R (Reverse). There should be no
movement while shifting the
transmission.
6. Shift the transmission to D (Drive).
7. If equipped with an ignition key, turn the ignition to ACC/ACCESSORY.
If equipped with Keyless Access, turn the
engine off. Disregard the Shift to P (Park)
DIC message. See Ignition Positions
(Keyless Access) 0230 or
Ignition Positions (Key Access) 0229.
{Warning
To avoid death, serious injury,
or property damage, before dinghy
towing the vehicle, always disconnect and
secure the negative battery cable and
cover the negative battery post and cable
with a non-conductive material. If the
battery is left connected or the battery
cable contacts the post, the Electric
Parking Brake may activate during
towing, which could cause a crash.
8. Disconnect the negative (–) battery cable. See “Negative Battery Cable
Disconnection” inBattery - North
America 0343.
9. Shift the transmission to P (Park).
Caution
If the steering column is locked, vehicle
damage may occur.
10. Move the steering wheel to make sure the steering column is unlocked.
11. If the vehicle has an ignition key, keep it in the towed vehicle in ACC/ACCESSORY
to prevent the steering column from
locking. If the vehicle is equipped with

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
398 Vehicle Care
Caution
Do not tow this vehicle with two wheels
on the ground, or vehicle damage could
occur. This damage would not be covered
by the vehicle warranty.
Dolly towing this vehicle is not allowed with
either the front or the rear tires on the
ground for two-wheel drive or four-wheel
drive, regardless of transfer case.
Appearance Care
Exterior Care
Locks
Locks are lubricated at the factory. Use a
de-icing agent only when absolutely
necessary, and have the locks greased after
using. See Recommended Fluids and
Lubricants 0418.
Washing the Vehicle
To preserve the vehicle's finish, wash it
often and out of direct sunlight.
{Warning
Do not power wash any part of the
vehicle’s interior, including the vinyl floor
covering. This could damage safety and
other systems in the vehicle, which
would not be covered by the vehicle
warranty.
Caution
Do not use petroleum-based, acidic,
or abrasive cleaning agents as they can
damage the vehicle's paint, metal,
or plastic parts. If damage occurs, it
would not be covered by the vehicle
warranty. Approved cleaning products can
be obtained from your dealer. Follow all
manufacturer directions regarding correct
product usage, necessary safety
precautions, and appropriate disposal of
any vehicle care product.
Caution
Avoid using high-pressure washes closer
than 30 cm (12 in) to the surface of the
vehicle. Use of power washers exceeding
8 274 kPa (1,200 psi) can result in
damage or removal of paint and decals.
Cleaning Underhood Components
Caution
Do not power wash any component
under the hood that has this
e
symbol.
This could cause damage that would not
be covered by the vehicle warranty.
Solvents or aggressive cleaners may harm
underhood components. The usages of these
chemicals should be avoided.
Recommend water only.
A pressure washer may be used, but care
must be utilized. The following criteria must
be followed:
.Water pressure must be kept below
14 000 KPa (2,000 PSI).
.Water temperature must be below 80 °C
(180 °F).

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Vehicle Care 405
Caution
Do not attach a device with a suction cup
to the display. This may cause damage
and would not be covered by the vehicle
warranty.
Instrument Panel, Leather, Vinyl, Other
Plastic Surfaces, Low Gloss Paint Surfaces
and Natural Open Pore Wood Surfaces
Use a soft microfiber cloth dampened with
water to remove dust and loose dirt. For a
more thorough cleaning, use a soft
microfiber cloth dampened with a mild soap
solution.
Caution
Soaking or saturating leather, especially
perforated leather, as well as other
interior surfaces, may cause permanent
damage. Wipe excess moisture from
these surfaces after cleaning and allow
them to dry naturally. Never use heat,
steam, or spot removers. Do not use
cleaners that contain silicone or
wax-based products. Cleaners containing
(Continued)
Caution (Continued)
these solvents can permanently change
the appearance and feel of leather or soft
trim, and are not recommended.
Do not use cleaners that increase gloss,
especially on the instrument panel. Reflected
glare can decrease visibility through the
windshield under certain conditions.
Caution
Use of air fresheners may cause
permanent damage to plastics and
painted surfaces. If an air freshener
comes in contact with any plastic or
painted surface in the vehicle, blot
immediately and clean with a soft cloth
dampened with a mild soap solution.
Damage caused by air fresheners would
not be covered by the vehicle warranty.
Care of Seat Belts
Keep belts clean and dry.
{Warning
Do not bleach or dye seat belt webbing.
It may severely weaken the webbing. In
a crash, they might not be able to
provide adequate protection. Clean and
rinse seat belt webbing only with mild
soap and lukewarm water. Allow the
webbing to dry.
Floor Mats
{Warning
If a floor mat, a liner, or a liner insert is
the wrong size or is not properly
installed, it can interfere with the pedals.
Interference with the pedals can cause
unintended acceleration and/or increased
stopping distance, which can cause a
crash and injury. Make sure the floor
mat, liner, or liner insert does not
interfere with the pedals.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Vehicle Care 407
Cleaning Rubber Floor Mats (All-Weather
Mats and Floor Liners)
{Warning
Do not use cleaners that contain silicone,
wax-based products, or cleaners that
increase gloss on rubber floor mats/liners.
These cleaners can permanently change
the appearance and feel of the rubber
and can make the floor mats/liners
slippery. Your foot could slip while
operating the vehicle, and you could lose
control, resulting in a crash. You or
others could be injured.
Use a soft cloth and/or a brush dampened
with water to remove dust and loose dirt.
For more thorough cleaning, use a mild soap
solution.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Service and Maintenance 409
Because of the way people use vehicles,
maintenance needs vary. There may need to
be more frequent checks and services. The
Additional Required Services - Normal are for
vehicles that:
.Carry passengers and cargo within
recommended limits on the Tire and
Loading Information label. SeeVehicle
Load Limits 0222.
.Are driven on reasonable road surfaces
within legal driving limits.
.Use the recommended fuel. See
Recommended Fuel (Except 6.2L
V8 Engine) 0283 or
Recommended Fuel (6.2L V8 Engine)
0 284.
Refer to the information in the Maintenance
Schedule Additional Required Services -
Normal chart.
The Additional Required Services - Severe are
for vehicles that are:
.Mainly driven in heavy city traffic in hot
weather
.Mainly driven in hilly or mountainous
terrain
.Frequently towing a trailer
.Used for high speed or competitive
driving
.Used for taxi, police, or delivery service
Refer to the information in the Maintenance
Schedule Additional Required Services -
Severe chart.
{Warning
Performing maintenance work can be
dangerous and can cause serious injury.
Perform maintenance work only if the
required information, proper tools, and
equipment are available. If they are not,
see your dealer to have a trained
technician do the work. See Doing Your
Own Service Work 0323.
Maintenance Schedule
Owner Checks and Services
Check the engine oil level. See Engine Oil
0 330.
Once a Month
.Check the tire inflation pressures,
including the spare. See Tire Pressure
0 367.
.Inspect the tires for wear. See Tire
Inspection 0373.
.Check the windshield washer fluid level.
See Washer Fluid 0340.
Engine Oil Change
When the CHANGE ENGINE OIL SOON
message displays, have the engine oil and
filter changed within the next 1 000 km/
600 mi. If driven under the best conditions,
the engine oil life system may not indicate
the need for vehicle service for up to a year.
The engine oil and filter must be changed at
least once a year and the oil life system
must be reset. Your trained dealer technician
can perform this work. If the engine oil life
system is reset accidentally, service the
vehicle within 5 000 km/3,000 mi since the
last service. Reset the oil life system when
the oil is changed. See Engine Oil Life
System 0332.
Engine Air Filter Change
When the REPLACE AT NEXT OIL CHANGE
message displays, the engine air filter
should be replaced at the next engine oil
change. When the REPLACE ENGINE AIR
FILTER SOON message displays, the engine
air filter should be replaced at the earliest
convenience. Reset the engine air filter life
system after the engine air filter is replaced.
See Engine Air Filter Life System 0333.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./Cana-
da/Mexico-14632426) - 2021 - CRC - 11/5/20
448 Index
IndexA
Accessories and Modifications . . . . . . . . . . . 323
Accessory Power . . . . . . . . . . . . . . . . . . . . . . . . . 236
Active Fuel Management . . . . . . . . . . . . . . . . 237
Adaptive Cruise Control . . . . . . . . . . . . . . . . . . 256
Add-On Electrical Equipment . . . . . . . . . . . . . .318
Adding a Snow Plow or SimilarEquipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .318
Additional Information OnStar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441
Additional Maintenance and Care . . . . . . . . .415
Adjustments Lumbar, Front Seats . . . . . . . . . . . . . . . . . . . . 48
Agreements
Trademarks and License . . . . . . . . . . . . . . . 195
Air Cleaner/Filter, Engine . . . . . . . . . . . . . . . . 334
Air Conditioning . . . . . . . . . . . . . . . . . . . . 204, 206
Air Filter Life System . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
Air Filter, Passenger Compartment . . . . . . . 209
Air Vents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
Airbag System Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
How Does an Airbag Restrain? . . . . . . . . . . 64
Passenger Sensing System . . . . . . . . . . . . . . 66
What Makes an Airbag Inflate? . . . . . . . . . 64
What Will You See after an AirbagInflates? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Airbag System (cont'd)
When Should an Airbag Inflate? . . . . . . . . 63
Where Are the Airbags? . . . . . . . . . . . . . . . . 62
Airbags Adding Equipment to the Vehicle . . . . . . . 69
Passenger Status Indicator . . . . . . . . . . . . . . 114
Readiness Light . . . . . . . . . . . . . . . . . . . . . . . . . 114
Servicing Airbag-Equipped Vehicles . . . . . . 69
System Check . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Alarm Vehicle Security . . . . . . . . . . . . . . . . . . . . . . . . . 31
Alert
Lane Change . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
Side Blind Zone (SBZA) . . . . . . . . . . . . . . . . . 280
All-Season Tires . . . . . . . . . . . . . . . . . . . . . . . . . . 361
All-Terrain Tires . . . . . . . . . . . . . . . . . . . . . . . . . . 362
AM-FM Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Antenna Fixed Mast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
Multi-band . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
Antilock Brake System (ABS) . . . . . . . . . . . . . 246
Warning Light . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Appearance Care Exterior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398
Interior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403
Apple CarPlay and Android Auto . . . . . . . . . .185