front end 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
20 Keys, Doors, and Windows
Remote Vehicle Start
If equipped with the remote start feature,
the climate control system will come on
when the vehicle is started remotely,
depending on the outside temperature.
The rear defog and heated and ventilated
seats, if equipped, may also come on. See
Heated and Ventilated Front Seats052 and
Vehicle Personalization 0131.
If equipped, the automatic heated steering
wheel may also come on. See Heated
Steering Wheel 0100.
Laws in some communities may restrict the
use of remote starters. Check local
regulations for any requirements on remote
starting of vehicles.
Do not use remote start if the vehicle is low
on fuel. The vehicle may run out of fuel.
The vehicle cannot be remote started if:
.The RKE transmitter is inside the vehicle
or if the key is in the ignition.
.The hood is not closed.
.There is an emission control system
malfunction and the lamp is on.
.The ignition is in any mode other
than off.
.The hazard warning flashers are on.
.Two remote starts or a remote start with
an extension have been used.
.The vehicle is not in P (Park).
The engine will turn off during a remote
vehicle start if:
.The coolant temperature gets too high.
.The oil pressure gets low.
The RKE transmitter range may be reduced
while the vehicle is running.
Other conditions can affect the performance
of the transmitter. See Remote Keyless Entry
(RKE) System 010.
Starting the Engine Using Remote Start
1. Press and release
Q.
2. Immediately press and hold
/until the
turn signal lamps flash or for at least
four seconds.
When the vehicle starts, the parking
lamps will turn on. The doors will be
locked and the climate control system
may come on. The engine will continue to run for
15 minutes. After 30 seconds, repeat
Steps 1 and 2 for a 15-minute time
extension.
Turn the ignition on to operate the vehicle.
Extending Engine Run Time
The engine run time can be extended by
15 minutes, for a total of 30 minutes,
if during the first 15 minutes Steps 1 and 2
are repeated while the engine is still
running. An extension can be requested
30 seconds after starting.
A maximum of two remote starts, or a
single start with an extension, is allowed
between ignition cycles.
The vehicle's ignition must be turned on and
then back off to use remote start again.
Canceling a Remote Start
To cancel a remote start, do one of the
following:
.Press and hold/until the parking lamps
turn off.
.Turn on the hazard warning flashers.
.Turn the ignition on and then off.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Seats and Restraints 45
Seats and Restraints
Head Restraints
Head Restraints . . . . . . . . . . . . . . . . . . . . . . . . 45
Front Seats
Seat Adjustment . . . . . . . . . . . . . . . . . . . . . . . 46
Center Seat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Power Seat Adjustment . . . . . . . . . . . . . . . . 47
Lumbar Adjustment . . . . . . . . . . . . . . . . . . . . 48
Reclining Seatbacks . . . . . . . . . . . . . . . . . . . . . 48
Memory Seats . . . . . . . . . . . . . . . . . . . . . . . . . 49
Heated and Ventilated Front Seats . . . . . 52
Rear Seats
Rear Seats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Heated Rear Seats . . . . . . . . . . . . . . . . . . . . . . 54
Seat Belts
Seat Belts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
How to Wear Seat Belts Properly . . . . . . . 55
Lap-Shoulder Belt . . . . . . . . . . . . . . . . . . . . . . . 57
Seat Belt Use During Pregnancy . . . . . . . . 59
Seat Belt Extender . . . . . . . . . . . . . . . . . . . . . . 59
Safety System Check . . . . . . . . . . . . . . . . . . . 60
Seat Belt Care . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Replacing Seat Belt System Parts after aCrash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Airbag System
Airbag System . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Where Are the Airbags? . . . . . . . . . . . . . . . . 62
When Should an Airbag Inflate? . . . . . . . . 63
What Makes an Airbag Inflate? . . . . . . . . 64
How Does an Airbag Restrain? . . . . . . . . . 64
What Will You See after an Airbag
Inflates? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Passenger Sensing System . . . . . . . . . . . . . 66
Servicing the Airbag-Equipped Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Adding Equipment to the Airbag-Equipped Vehicle . . . . . . . . . . . . . . 69
Airbag System Check . . . . . . . . . . . . . . . . . . . 70
Replacing Airbag System Parts after a Crash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Child Restraints
Older Children . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Infants and Young Children . . . . . . . . . . . . . 72
Child Restraint Systems . . . . . . . . . . . . . . . . 74
Where to Put the Restraint . . . . . . . . . . . . . 76
Lower Anchors and Tethers for Children(LATCH System) . . . . . . . . . . . . . . . . . . . . . . . 77
Replacing LATCH System Parts After a Crash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Securing Child Restraints (With the Seat Belt in the Rear Seat) . . . . . . . . . . . . . . . . 88
Securing Child Restraints (With the Seat Belt in the Center Front Seat) . . . . . . . . 92
Securing Child Restraints (With the Seat Belt in the Front Passenger Seat) . . . . . 92
Head Restraints
{
Warning
With head restraints that are not
installed and adjusted properly, there is a
greater chance that occupants will suffer
a neck/spinal injury in a crash. Do not
drive until the head restraints for all
occupants are installed and adjusted
properly.
Front Seats
The vehicle's front seats have adjustable
head restraints in the outboard seating
positions.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
52 Seats and Restraints
Obstructions
If something has blocked the driver seat
while recalling a memory position, the recall
may stop. Remove the obstruction and try
the recall again. If the memory position still
does not recall, see your dealer.
Heated and Ventilated Front
Seats
{Warning
If temperature change or pain to the skin
cannot be felt, the seat heater may cause
burns. To reduce the risk of burns, use
care when using the seat heater,
especially for long periods of time. Do
not place anything on the seat that
insulates against heat, such as a blanket,
cushion, cover, or similar item. This may
cause the seat heater to overheat. An
overheated seat heater may cause a burn
or may damage the seat.Heated and Ventilated Seat Buttons Shown,Heated Seat Buttons Similar
If equipped, the buttons are on the center
stack. To operate, the engine must be
running.
Press
Ior+to heat the driver or
passenger seatback only.
Press
Jorzto heat the driver or
passenger seat cushion and seatback.
Press
Cor{to ventilate the driver or
passenger seat.
The indicator light on the button comes on
when this feature is on. Press the button once for the highest
setting. With each press of the button, the
seat will change to the next lower setting,
and then to the off setting. The indicator
lights next to the buttons indicate three for
the highest setting and one for the lowest.
If the heated seats are on high for an
extended time, their level may automatically
be lowered.
Auto Heated Seats
When the vehicle is on, this feature will
automatically activate the heated seats at
the level required by the vehicle’s interior
temperature. The active high, medium, low,
or off heated seat level will be indicated by
the manual heated seat buttons on the
center stack. Use the manual heated seat
buttons on the center stack to turn auto
heated seats off. If the passenger seat is
unoccupied, the auto heated seats feature
will not activate that seat. The auto heated
seats feature can be programmed to always
be enabled when the vehicle is on. See
Vehicle Personalization
0131.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
58 Seats and Restraints
position on the seat, move the seat
rearward or recline the seat until the
shoulder belt retractor lock releases.
Engaging the child restraint locking
feature in the front outboard seating
position may affect the passenger
sensing system, if equipped. See
Passenger Sensing System066.
If the webbing locks in the latch plate
before it reaches the buckle, tilt the latch
plate flat to unlock.
3. Push the latch plate into the buckle until
it clicks.
Pull up on the latch plate to make sure
it is secure. If the belt is not long
enough, see Seat Belt Extender 059.
Position the release button on the buckle
so that the seat belt could be quickly
unbuckled if necessary.4. To make the lap part tight, pull up on the shoulder belt.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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Seats and Restraints 59
To unlatch the belt, push the button on the
buckle. The belt should return to its stowed
position.
Always stow the seat belt slowly. If the seat
belt webbing returns quickly to the stowed
position, the retractor may lock and cannot
be pulled out. If this happens, pull the seat
belt straight out firmly to unlock the
webbing, and then release it. If the webbing
is still locked in the retractor, see your
dealer.
Before a door is closed, be sure the seat belt
is out of the way. If a door is slammed
against a seat belt, damage can occur to
both the seat belt and the vehicle.
Seat Belt Pretensioners
This vehicle has seat belt pretensioners for
the front outboard occupants. Although the
seat belt pretensioners cannot be seen, they
are part of the seat belt assembly. They can
help tighten the seat belts during the early
stages of a moderate to severe frontal, near
frontal, or rear crash if the threshold
conditions for pretensioner activation are
met. Seat belt pretensioners can also help
tighten the seat belts in a side crash or
rollover event.Pretensioners work only once. If the
pretensioners activate in a crash, the
pretensioners and probably other parts of
the vehicle's seat belt system will need to
be replaced. See
Replacing Seat Belt System
Parts after a Crash 060.
Do not sit on the outboard seat belt while
entering or exiting the vehicle or at any
time while sitting in the seat. Sitting on the
seat belt can damage the webbing and
hardware.
Rear Seat Belt Comfort Guides
Rear seat belt comfort guides may provide
added seat belt comfort for older children
who have outgrown booster seats and for
some adults. When installed on a shoulder
belt, the comfort guide positions the
shoulder belt away from the neck and head.
Comfort guides are available through your
dealer for the rear outboard seating
positions. Instructions are included with the
comfort guides.
Seat Belt Use During Pregnancy
Seat belts work for everyone, including
pregnant women. Like all occupants, they
are more likely to be seriously injured if
they do not wear seat belts.
A pregnant woman should wear a
lap-shoulder belt, and the lap portion should
be worn as low as possible, below the
rounding, throughout the pregnancy.
The best way to protect the fetus is to
protect the mother. When a seat belt is
worn properly, it is more likely that the
fetus will not be hurt in a crash. For
pregnant women, as for anyone, the key to
making seat belts effective is wearing them
properly.
Seat Belt Extender
If the vehicle's seat belt will fasten around
you, you should use it.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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64 Seats and Restraints
Frontal airbags are designed to inflate in
moderate to severe frontal or near frontal
crashes to help reduce the potential for
severe injuries, mainly to the driver's or
front outboard passenger's head and chest.
Whether the frontal airbags will or should
inflate is not based primarily on how fast
the vehicle is traveling. It depends on what
is hit, the direction of the impact, and how
quickly the vehicle slows down.
Frontal airbags may inflate at different crash
speeds depending on whether the vehicle
hits an object straight on or at an angle,
and whether the object is fixed or moving,
rigid or deformable, narrow or wide.
Frontal airbags are not intended to inflate
during vehicle rollovers, rear impacts,
or many side impacts.
In addition, the vehicle has advanced
technology frontal airbags. Advanced
technology frontal airbags adjust the
restraint according to crash severity.
Seat-mounted side impact airbags are
designed to inflate in moderate to severe
side crashes depending on the location of
the impact. Seat-mounted side impact
airbags are not designed to inflate in frontal
impacts, near frontal impacts, rollovers,or rear impacts. A seat-mounted side impact
airbag is designed to inflate on the side of
the vehicle that is struck.
Roof-rail airbags are designed to inflate in
moderate to severe side crashes depending
on the location of the impact. In addition,
these roof-rail airbags are designed to inflate
during a rollover or in a severe frontal
impact. Roof-rail airbags are not designed to
inflate in rear impacts. Both roof-rail airbags
will inflate when either side of the vehicle is
struck or if the sensing system predicts that
the vehicle is about to roll over on its side,
or in a severe frontal impact.
In any particular crash, no one can say
whether an airbag should have inflated
simply because of the vehicle damage or
repair costs.
What Makes an Airbag Inflate?
In a deployment event, the sensing system
sends an electrical signal triggering a release
of gas from the inflator. Gas from the
inflator fills the airbag causing the bag to
break out of the cover. The inflator, the
airbag, and related hardware are all part of
the airbag module.
For airbag locations, see
Where Are the
Airbags? 062.
How Does an Airbag Restrain?
In moderate to severe frontal or near frontal
collisions, even belted occupants can contact
the steering wheel or the instrument panel.
In moderate to severe side collisions, even
belted occupants can contact the inside of
the vehicle.
Airbags supplement the protection provided
by seat belts by distributing the force of the
impact more evenly over the
occupant's body.
Rollover capable roof-rail airbags are
designed to help contain the head and chest
of occupants in the outboard seating
positions in the first and second rows. The
rollover capable roof-rail airbags are
designed to help reduce the risk of full or
partial ejection in rollover events, although
no system can prevent all such ejections.
But airbags would not help in many types
of collisions, primarily because the
occupant's motion is not toward those
airbags. See When Should an Airbag Inflate?
0 63.
Airbags should never be regarded as
anything more than a supplement to seat
belts.

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Seats and Restraints 67
Warning (Continued)
Never put a rear-facing child restraint in
the front seat, even if the airbag is off.
If securing a forward-facing child restraint
in the front outboard passenger seat,
always move the seat as far back as it
will go. It is better to secure child
restraints in the rear seat. Consider using
another vehicle to transport the child
when a rear seat is not available.
If the vehicle does not have a rear seat that
will accommodate a rear-facing child
restraint, a rear-facing child restraint should
not be installed in the vehicle, even if the
airbag is off.
The passenger sensing system is designed to
turn off the front outboard passenger
frontal airbag if:
.The front outboard passenger seat is
unoccupied.
.The system determines an infant is
present in a child restraint.
.A front outboard passenger takes his/her
weight off of the seat for a period
of time.
.There is a critical problem with the airbag
system or the passenger sensing system.
When the passenger sensing system has
turned off the front outboard passenger
frontal airbag, the OFF indicator will light
and stay lit as a reminder that the airbag is
off. See Passenger Airbag Status Indicator
0 114.
The passenger sensing system is designed to
turn on the front outboard passenger frontal
airbag anytime the system senses that a
person of adult size is sitting properly in the
front outboard passenger seat.
When the passenger sensing system has
allowed the airbag to be enabled, the ON
indicator will light and stay lit as a reminder
that the airbag is active.
For some children, including children in child
restraints, and for very small adults, the
passenger sensing system may or may not
turn off the front outboard passenger
frontal airbag, depending upon the person's
seating posture and body build. Everyone in
the vehicle who has outgrown child
restraints should wear a seat belt
properly —whether or not there is an
airbag for that person.{Warning
If the airbag readiness light ever comes
on and stays on, it means that
something may be wrong with the airbag
system. To help avoid injury to yourself
or others, have the vehicle serviced right
away. See Airbag Readiness Light 0114
for more information, including important
safety information.
If the On Indicator Is Lit for a Child
Restraint
The passenger sensing system is designed to
turn off the front outboard passenger
frontal airbag if the system determines that
an infant is present in a child restraint. If a
child restraint has been installed and the ON
indicator is lit:
1. Turn the vehicle off.
2. Remove the child restraint from the vehicle.
3. Remove any additional items from the seat such as blankets, cushions, seat
covers, seat heaters, or seat massagers.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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68 Seats and Restraints
4. Reinstall the child restraint following thedirections provided by the child restraint
manufacturer and refer to Securing Child
Restraints (With the Seat Belt in the
Center Front Seat) 092 or
Securing Child Restraints (With the Seat
Belt in the Rear Seat) 088 or
Securing Child Restraints (With the Seat
Belt in the Front Passenger Seat) 092.
Make sure the seat belt retractor is
locked by pulling the shoulder belt all
the way out of the retractor when
installing the child restraint, even if the
child restraint is equipped with a seat
belt lock off. When the retractor lock is
set, the belt can be tightened but not
pulled out of the retractor.
5. If, after reinstalling the child restraint and restarting the vehicle, the ON
indicator is still lit, turn the vehicle off.
Then slightly recline the vehicle seatback
and adjust the seat cushion,
if adjustable, to make sure that the
vehicle seatback is not pushing the child
restraint into the seat cushion.
Also make sure the child restraint is not
trapped under the vehicle head restraint.
If this happens, adjust the head restraint.
See Head Restraints 045. 6. Restart the vehicle.
The passenger sensing system may or may
not turn off the airbag for a child in a child
restraint depending upon the child’s size.
It is better to secure child restraints in the
rear seat. Consider using another vehicle to
transport the child when a rear seat is not
available. Never put a rear-facing child
restraint in the front seat, even if the ON
indicator is not lit.
If the Off Indicator Is Lit for an
Adult-Sized Occupant
If a person of adult size is sitting in the
front outboard passenger seat, but the OFF
indicator is lit, it could be because that
person is not sitting properly in the seat or that the child restraint locking feature is
engaged. Use the following steps to allow
the system to detect that person and enable
the front outboard passenger frontal airbag:
1. Turn the vehicle off.
2. Remove any additional material from the seat, such as blankets, cushions, seat
covers, seat heaters, or seat massagers.
3. Place the seatback in the fully upright position.
4. Have the person sit upright in the seat, centered on the seat cushion, with legs
comfortably extended.
5. If the shoulder portion of the belt is pulled out all the way, the child restraint
locking feature will be engaged. This
may unintentionally cause the passenger
sensing system to turn the airbag off for
some adult-sized occupants. If this
happens, unbuckle the belt, let the belt
go back all the way, and then buckle the
belt again without pulling the belt out
all the way.
6. Restart the vehicle and have the person remain in this position for two to
three minutes after the ON indicator
is lit.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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Seats and Restraints 69
{Warning
If the front outboard passenger airbag is
turned off for an adult-sized occupant,
the airbag will not be able to inflate and
help protect that person in a crash,
resulting in an increased risk of serious
injury or even death. An adult-sized
occupant should not ride in the front
outboard passenger seat, if the passenger
airbag OFF indicator is lit.
Additional Factors Affecting System
Operation
Seat belts help keep the passenger in
position on the seat during vehicle
maneuvers and braking, which helps the
passenger sensing system maintain the
passenger airbag status. See“Seat Belts”
and “Child Restraints” in the Index for
additional information about the importance
of proper restraint use.
A thick layer of additional material, such as
a blanket or cushion, or aftermarket
equipment such as seat covers, seat heaters,
and seat massagers can affect how well the
passenger sensing system operates. We
recommend that you not use seat covers or
other aftermarket equipment except when approved by GM for your specific vehicle.
See
Adding Equipment to the
Airbag-Equipped Vehicle 069 for more
information about modifications that can
affect how the system operates.
The ON indicator may be lit if an object,
such as a briefcase, handbag, grocery bag,
laptop, or other electronic device, is put on
an unoccupied seat. If this is not desired,
remove the object from the seat.
{Warning
Stowing articles under the passenger seat
or between the passenger seat cushion
and seatback may interfere with the
proper operation of the passenger
sensing system.
Servicing the Airbag-Equipped
Vehicle
Airbags affect how the vehicle should be
serviced. There are parts of the airbag
system in several places around the vehicle.
Your dealer and the service manual have
information about servicing the vehicle and
the airbag system. To purchase a service
manual, see Publication Ordering
Information 0435.
{Warning
For up to 10 seconds after the vehicle is
turned off and the battery is
disconnected, an airbag can still inflate
during improper service. You can be
injured if you are close to an airbag
when it inflates. Avoid yellow connectors.
They are probably part of the airbag
system. Be sure to follow proper service
procedures, and make sure the person
performing work for you is qualified to
do so.
Adding Equipment to the
Airbag-Equipped Vehicle
Adding accessories that change the vehicle's
frame, bumper system, height, front end,
or side sheet metal, may keep the airbag
system from working properly.
The operation of the airbag system can also
be affected by changing, including
improperly repairing or replacing, any parts
of the following:
.Airbag system, including airbag modules,
front or side impact sensors, sensing and
diagnostic module, or airbag wiring

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Seats and Restraints 73
Warning (Continued)
tighten but cannot be loosened if it is
locked. The shoulder belt locks when it is
pulled all the way out of the retractor.
It unlocks when the shoulder belt is
allowed to go all the way back into the
retractor, but it cannot do this if it is
wrapped around a child’s neck. If the
shoulder belt is locked and tightened
around a child’s neck, the only way to
loosen the belt is to cut it.
Never leave children unattended in a
vehicle and never allow children to play
with the seat belts.
Every time infants and young children ride
in vehicles, they should have the protection
provided by appropriate child restraints.
Neither the vehicle's seat belt system nor its
airbag system is designed for them.
Children who are not restrained properly can
strike other people, or can be thrown out of
the vehicle.
{Warning
Never hold an infant or a child while
riding in a vehicle. Due to crash forces, an
infant or a child will become so heavy it
is not possible to hold it during a crash.
For example, in a crash at only
40 km/h (25 mph), a 5.5 kg (12 lb) infant
will suddenly become a 110 kg (240 lb)
force on a person's arms. An infant or
child should be secured in an appropriate
child restraint.
{Warning
Children who are up against, or very
close to, any airbag when it inflates can
be seriously injured or killed. Never put a
rear-facing child restraint in the front
outboard seat. Secure a rear-facing child
restraint in a rear seat. It is also better to
secure a forward-facing child restraint in
a rear seat. If you must secure a
forward-facing child restraint in the front
outboard seat, always move the front
passenger seat as far back as it will go.
Child restraints are devices used to restrain,
seat, or position children in the vehicle and
are sometimes called child seats or car seats.