2021 GMC SIERRA heater

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
54 Seats and Restraints
To return the seat to the normal seating
position, slowly pull the seat cushion down.
{Warning
A seat belt that is improperly routed, not
properly attached, or twisted will not
provide the protection needed in a crash.
The person wearing the belt could be
seriously injured. After raising the rear
seatback, always check to be sure that
the seat belts are properly routed and
attached, and are not twisted.
Heated Rear Seats
{Warning
If you cannot feel temperature change or
pain to the skin, the seat heater may
cause burns. See the Warning under
Heated and Ventilated Front Seats052.
If available, the buttons are on the rear of
the center console. To operate, the engine
must be running.
Press
MorLto heat the left or right
outboard seat cushion. An indicator on the
climate control display appears when this
feature is on.
This feature turns on at the highest setting.
With each press of the button, the heated
seat changes to the next lower setting, and
then the off setting. Three lights indicate
the highest setting, and one light indicates
the lowest. If the heated seats are on high,
the level may automatically be lowered
after approximately 30 minutes.
Seat Belts
This section describes how to use seat belts
properly, and some things not to do.
{Warning
Do not let anyone ride where a seat belt
cannot be worn properly. In a crash,
if you or your passenger(s) are not
wearing seat belts, injuries can be much
worse than if you are wearing seat belts.
You can be seriously injured or killed by
hitting things inside the vehicle harder or
by being ejected from the vehicle. In
addition, anyone who is not buckled up
can strike other passengers in the vehicle.
It is extremely dangerous to ride in a
cargo area, inside or outside of a vehicle.
In a collision, passengers riding in these
areas are more likely to be seriously
injured or killed. Do not allow passengers
to ride in any area of the vehicle that is
not equipped with seats and seat belts.
Always wear a seat belt, and check that
all passenger(s) are restrained
properly too.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
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./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
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./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
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

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
70 Seats and Restraints
.Front seats, including stitching, seams,
or zippers
.Seat belts
.Steering wheel, instrument panel,
overhead console, ceiling trim, or pillar
garnish trim
.Inner door seals, including speakers
Your dealer and the service manual have
information about the location of the airbag
modules and sensors, sensing and diagnostic
module, and airbag wiring along with the
proper replacement procedures.
In addition, the vehicle has a passenger
sensing system for the front outboard
passenger position, which includes sensors
that are part of the passenger seat. The
passenger sensing system may not operate
properly if the original seat trim is replaced
with non-GM covers, upholstery, or trim; or
with GM covers, upholstery, or trim
designed for a different vehicle. Any object,
such as an aftermarket seat heater or a
comfort-enhancing pad or device, installed
under or on top of the seat fabric, could
also interfere with the operation of the
passenger sensing system. This could either
prevent proper deployment of the passenger
airbag(s) or prevent the passenger sensing system from properly turning off the
passenger airbag(s). See
Passenger Sensing
System 066.
If the vehicle has rollover roof-rail airbags,
see Different Size Tires and Wheels 0377 for
additional important information.
If a snow plow is added to the vehicle, the
airbags should still work properly. The
airbag systems were designed to work
properly under a wide range of conditions,
including snow plowing with vehicles that
have the optional snow plow prep package
(RPO VYU). Do not change or defeat the
snow plow's “tripping mechanism.” If you
do, it can damage the snow plow and the
vehicle, and may cause an airbag
deployment.
If the vehicle must be modified because you
have a disability and have questions about
whether the modifications will affect the
vehicle's airbag system, or if you have
questions about whether the airbag system
will be affected if the vehicle is modified for
any other reason, call Customer Assistance.
See Customer Assistance Offices 0430.
Airbag System Check
The airbag system does not need regularly
scheduled maintenance or replacement.
Make sure the airbag readiness light is
working. See Airbag Readiness Light 0114.
Caution
If an airbag covering is damaged, opened,
or broken, the airbag may not work
properly. Do not open or break the airbag
coverings. If there are any opened or
broken airbag coverings, have the airbag
covering and/or airbag module replaced.
For the location of the airbags, see Where
Are the Airbags? 062. See your dealer
for service.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 211
Driving and Operating
Driving Information
Driving for Better Fuel Economy . . . . . . . 212
Distracted Driving . . . . . . . . . . . . . . . . . . . . . . 212
Defensive Driving . . . . . . . . . . . . . . . . . . . . . . 213
Impaired Driving . . . . . . . . . . . . . . . . . . . . . . . 213
Control of a Vehicle . . . . . . . . . . . . . . . . . . . . 213
Braking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
Steering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
Off-Road Recovery . . . . . . . . . . . . . . . . . . . . . 214
Loss of Control . . . . . . . . . . . . . . . . . . . . . . . . . 215
Off-Road Driving . . . . . . . . . . . . . . . . . . . . . . . 215
Driving on Wet Roads . . . . . . . . . . . . . . . . . 219
Hill and Mountain Roads . . . . . . . . . . . . . . 219
Winter Driving . . . . . . . . . . . . . . . . . . . . . . . . 220
If the Vehicle Is Stuck . . . . . . . . . . . . . . . . . . 221
Vehicle Load Limits . . . . . . . . . . . . . . . . . . . . 222
Truck-Camper Loading Information . . . . 226
Starting and Operating
New Vehicle Break-In . . . . . . . . . . . . . . . . . . 228
Ignition Positions (Key Access) . . . . . . . . 229
Ignition Positions (Keyless Access) . . . . . 230
Starting the Engine . . . . . . . . . . . . . . . . . . . . 232
Stop/Start System . . . . . . . . . . . . . . . . . . . . . 233
Engine Heater . . . . . . . . . . . . . . . . . . . . . . . . . 234
Retained Accessory Power (RAP) . . . . . . . 236
Shifting Into Park . . . . . . . . . . . . . . . . . . . . . 236
Shifting out of Park . . . . . . . . . . . . . . . . . . . 237Parking over Things That Burn . . . . . . . . . 237
Active Fuel Management . . . . . . . . . . . . . . 237
Extended Parking . . . . . . . . . . . . . . . . . . . . . . 238
Engine Exhaust
Engine Exhaust . . . . . . . . . . . . . . . . . . . . . . . . 238
Running the Vehicle While Parked . . . . . 238
Automatic Transmission
Automatic Transmission . . . . . . . . . . . . . . . 239
Manual Mode . . . . . . . . . . . . . . . . . . . . . . . . . 241
Tow/Haul Mode . . . . . . . . . . . . . . . . . . . . . . . 242
Drive Systems
Four-Wheel Drive . . . . . . . . . . . . . . . . . . . . . . 242
Brakes
Electric Brake Boost . . . . . . . . . . . . . . . . . . . 246
Antilock Brake System (ABS) . . . . . . . . . . 246
Electric Parking Brake . . . . . . . . . . . . . . . . . . 247
Brake Assist . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
Hill Start Assist (HSA) . . . . . . . . . . . . . . . . . 248
Ride Control Systems
Traction Control/Electronic Stability
Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
Hill Descent Control (HDC) . . . . . . . . . . . . 250
Driver Mode Control . . . . . . . . . . . . . . . . . . . 251
Limited-Slip Differential . . . . . . . . . . . . . . . . 254
Locking Rear Axle . . . . . . . . . . . . . . . . . . . . . 254
Cruise Control
Cruise Control . . . . . . . . . . . . . . . . . . . . . . . . . 254
Adaptive Cruise Control (Camera) . . . . . . 256
Driver Assistance Systems
Driver Assistance Systems . . . . . . . . . . . . . 265
Assistance Systems for Parking or Backing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
Assistance Systems for Driving . . . . . . . . 274
Forward Collision Alert (FCA) System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
Automatic Emergency Braking (AEB) . . . 277
Front Pedestrian Braking (FPB) System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278
Side Blind Zone Alert (SBZA) . . . . . . . . . . 280
Lane Change Alert (LCA) . . . . . . . . . . . . . . . 280
Lane Keep Assist (LKA) . . . . . . . . . . . . . . . . . 281
Fuel
Top Tier Fuel . . . . . . . . . . . . . . . . . . . . . . . . . . 283
Recommended Fuel (Except 6.2L V8 Engine) . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
Recommended Fuel (6.2L V8 Engine) . . . . . . . . . . . . . . . . . . . . . . . . . . 284
Prohibited Fuels . . . . . . . . . . . . . . . . . . . . . . . 284
Fuels in Foreign Countries . . . . . . . . . . . . . 284
Fuel Additives . . . . . . . . . . . . . . . . . . . . . . . . . 284
E85 or FlexFuel . . . . . . . . . . . . . . . . . . . . . . . . 284
Filling the Tank (Pickup Model) . . . . . . . . 285
Filling the Tank (Chassis Cab Model) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
234 Driving and Operating
.The driver door has been opened or the
driver seat belt has been unbuckled.
.The hood has been opened.
.The Auto Stop has reached the maximum
allowed time.
Auto Stop Disable Switch
If equipped, the automatic engine Stop/Start
feature can be disabled and enabled by
pressing the switch with the
hsymbol.
Auto Stop is enabled each time you start
the vehicle.
When
his illuminated, the system is
enabled.
Engine Heater
If equipped, the engine heater can provide
easier starting and better fuel economy
during engine warm-up in cold weather
conditions at or below −18 °C (0 °F). Vehicles
with an engine heater should be plugged in
at least four hours before starting. An
internal thermostat in the plug-end of the
cord may exist, which will prevent engine
heater operation at temperatures above
−18 °C (0 °F).
{Warning
Do not plug in the engine block heater
while the vehicle is parked in a garage or
under a carport. Property damage or
personal injury may result. Always park
the vehicle in a clear open area away
from buildings or structures.
Base Model shown other models are similar
To Use the Engine Heater
1. Turn off the engine.
2. Check the heater cord for damage. If it is damaged, do not use it. See your dealer
for a replacement. Inspect the cord for
damage yearly.