climate control 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
290 Driving and Operating
{Warning
To prevent serious injury or death from
carbon monoxide (CO), when towing a
trailer:
.Do not drive with the liftgate, trunk/
hatch, or rear-most window open.
.Fully open the air outlets on or under
the instrument panel.
.Adjust the climate control system to a
setting that brings in only outside air.
See“Climate Control Systems” in the
Index.
For more information about carbon
monoxide, see Engine Exhaust 0238.
Towing a trailer requires experience. The
combination of the vehicle and trailer is
longer and not as responsive as the vehicle
itself. Get used to the handling and braking
of the combination by driving on a level
road surface before driving on public roads.
The trailer structure, the tires, and the
brakes must all be rated to carry the
intended cargo. Inadequate trailer
equipment can cause the combination to
operate in an unexpected or unsafe manner.
Before driving, inspect all trailer hitch parts and attachments, safety chains, electrical
connectors, lamps, tires, and mirrors. See
Towing Equipment
0296. If the trailer has
electric brakes, start the combination
moving and then manually apply the trailer
brake controller to check that the trailer
brakes work. During the trip, occasionally
check that the cargo and trailer are secure
and that the lamps and any trailer brakes
are working.Towing with a Stability Control System
When towing, the stability control system
might be heard. The system reacts to
vehicle movement caused by the trailer,
which mainly occurs during cornering. This is
normal when towing heavier trailers.
Following Distance
Stay at least twice as far behind the vehicle
ahead as you would when driving without a
trailer. This can help to avoid heavy braking
and sudden turns.
Passing
More passing distance is needed when
towing a trailer. The combination of the
vehicle and trailer will not accelerate as
quickly and is much longer than the vehicle
alone. It is necessary to go much farther beyond the passed vehicle before returning
to the lane. Pass on level roadways. Avoid
passing on hills if possible.
Backing Up
Hold the bottom of the steering wheel with
one hand. To move the trailer to the left,
move that hand to the left. To move the
trailer to the right, move that hand to the
right. Always back up slowly and, if possible,
have someone guide you.
Making Turns
Caution
Turn more slowly and make wider arcs
when towing a trailer to prevent damage
to your vehicle. Making very sharp turns
could cause the trailer to contact the
vehicle.
Make wider turns than normal when towing,
so the trailer will not go over soft shoulders,
over curbs, or strike road signs, trees,
or other objects. Always signal turns well in
advance. Do not steer or brake suddenly.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
378 Vehicle Care
times as well on the government course
as a tire graded 100. The relative
performance of tires depends upon the
actual conditions of their use, however,
and may depart significantly from the
norm due to variations in driving habits,
service practices and differences in road
characteristics and climate.
Traction
The traction grades, from highest to
lowest, are AA, A, B, and C. Those
grades represent the tire's ability to
stop on wet pavement as measured
under controlled conditions on specified
government test surfaces of asphalt and
concrete. A tire marked C may have
poor traction performance. Warning:
The traction grade assigned to this tire
is based on straight-ahead braking
traction tests, and does not include
acceleration, cornering, hydroplaning,
or peak traction characteristics.Temperature
The temperature grades are A (the
highest), B, and C, representing the
tire's resistance to the generation of
heat and its ability to dissipate heat
when tested under controlled conditions
on a specified indoor laboratory test
wheel. Sustained high temperature can
cause the material of the tire to
degenerate and reduce tire life, and
excessive temperature can lead to
sudden tire failure. The grade C
corresponds to a level of performance
which all passenger car tires must meet
under the Federal Motor Safety
Standard No. 109. Grades B and A
represent higher levels of performance
on the laboratory test wheel than the
minimum required by law. Warning:
The temperature grade for this tire is
established for a tire that is properly
inflated and not overloaded. Excessive
speed, underinflation, or excessive
loading, either separately or in
combination, can cause heat buildup
and possible tire failure.Wheel Alignment and Tire
Balance
The tires and wheels were aligned and
balanced at the factory to provide the
longest tire life and best overall
performance. Adjustments to wheel
alignment and tire balancing are not
necessary on a regular basis. Consider an
alignment check if there is unusual tire wear
or the vehicle is significantly pulling to one
side or the other. Some slight pull to the
left or right, depending on the crown of the
road and/or other road surface variations
such as troughs or ruts, is normal. If the
vehicle is vibrating when driving on a
smooth road, the tires and wheels may
need to be rebalanced. See your dealer for
proper diagnosis.
Wheel Replacement
Replace any wheel that is bent, cracked,
or badly rusted or corroded. If wheel nuts
keep coming loose, the wheel, wheel bolts,
and wheel nuts should be replaced. If the
wheel leaks air, replace it. Some aluminum
wheels can be repaired. See your dealer if
any of these conditions exist.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./Cana-
da/Mexico-14632426) - 2021 - CRC - 11/5/20
450 Index
Caution, Danger, and Warning . . . . . . . . . . . . . .2
Center Console Storage . . . . . . . . . . . . . . . . . . . 96
Center High-Mounted Stoplamp(CHMSL) and Cargo Lamp . . . . . . . . . . . . . . 352
Center Seat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Chains, Tire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
Charging Wireless . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Charging System Light . . . . . . . . . . . . . . . . . . . . 115
Check Engine Light (Malfunction Indicator) . . . . 115
Ignition Transmission Lock . . . . . . . . . . . . . 347
Child Restraints Infants and Young Children . . . . . . . . . . . . . 72
Lower Anchors and Tethers forChildren . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Older Children . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Securing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88, 92
Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Circuit Breakers . . . . . . . . . . . . . . . . . . . . . . . . . . 353
Cleaning Exterior Care . . . . . . . . . . . . . . . . . . . . . . . . . . . 398
Interior Care . . . . . . . . . . . . . . . . . . . . . . . . . . . 403
Climate Control Systems . . . . . . . . . . . . . . . . . 204 Air Conditioning . . . . . . . . . . . . . . . . . . . . . . . 204
Dual Automatic . . . . . . . . . . . . . . . . . . . . . . . . 206
Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Cluster, Instrument . . . . . . . . . . . . . . . . . . . . . . 106
Collision Damage Repair . . . . . . . . . . . . . . . . . 434
Compartments
Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Compass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Connected Services Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . 446
Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447
Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445
Connections Connected Services . . . . . . . . . . . . . . . . . . . . 446
Control Hill Descent . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
Traction and Electronic Stability . . . . . . . 248
Control Light Hill Descent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Control of a Vehicle . . . . . . . . . . . . . . . . . . . . . . 213
Controls Steering Wheel . . . . . . . . . . . . . . . . . . . . . . . . . 151
Convex Mirrors . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Coolant Engine Temperature Gauge . . . . . . . . . . . . . 112
Engine Temperature Warning Light . . . . . 121
Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204, 206
Cooling System . . . . . . . . . . . . . . . . . . . . . . . . . . 335
Courtesy Transportation Program . . . . . . . . 433
Coverage Explanations . . . . . . . . . . . . . . . . . . . . 175
Cruise Control . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 Cruise Control (cont'd)
Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
Cruise Control, Adaptive . . . . . . . . . . . . . . . . . 256
Cupholders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Customer Assistance . . . . . . . . . . . . . . . . . . . . . 430 Offices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430
Text Telephone (TTY) Users . . . . . . . . . . . . 430
Customer Information Publications Ordering Information . . . . . 435
Customer Satisfaction Procedure . . . . . . . . . 428
Cybersecurity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438
D
Damage Repair, Collision . . . . . . . . . . . . . . . . . 434
Danger, Warning, and Caution . . . . . . . . . . . . . .2
Data Collection Infotainment System . . . . . . . . . . . . . . . . . . 439
OnStar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
Data Recorders, Event . . . . . . . . . . . . . . . . . . . 438
Database Coverage Explanations . . . . . . . . . . 175
Daytime Running Lamps (DRL) . . . . . . . . . . . . 141
Defensive Driving . . . . . . . . . . . . . . . . . . . . . . . . . 213
Delayed Locking . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Destination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
Diagnostics Connected Services . . . . . . . . . . . . . . . . . . . . 447
Differential, Limited-Slip . . . . . . . . . . . . . . . . . 254
Distracted Driving . . . . . . . . . . . . . . . . . . . . . . . . . 212

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./Cana-
da/Mexico-14632426) - 2021 - CRC - 11/5/20
Index 451
Dome Lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145
DoorAjar Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
Delayed Locking . . . . . . . . . . . . . . . . . . . . . . . . 22
Locks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Power Locks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Drive Belt Routing, Engine . . . . . . . . . . . . . . . 427
Driver
Teen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
Driver Assistance Systems . . . . . . . . . . . . . . . 265
Driver Information Center (DIC) . . . . . . 124, 125
Driver Mode Control . . . . . . . . . . . . . . . . . . . . . . 251
Driver Mode Control Light . . . . . . . . . . . . . . . . 121
Driving Assistance Systems . . . . . . . . . . . . . . . . . . . . 274
Better Fuel Economy . . . . . . . . . . . . . . . . . . . 212
Characteristics and Towing Tips . . . . . . . . 288
Defensive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
Hill and Mountain Roads . . . . . . . . . . . . . . 219
If the Vehicle is Stuck . . . . . . . . . . . . . . . . . 221
Impaired . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
Loss of Control . . . . . . . . . . . . . . . . . . . . . . . . 215
Off-Road . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
Off-Road Recovery . . . . . . . . . . . . . . . . . . . . . 214
Vehicle Load Limits . . . . . . . . . . . . . . . . . . . . 222
Wet Roads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
Winter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 Dual Automatic Climate Control
System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
E
E85 or FlexFuel . . . . . . . . . . . . . . . . . . . . . . . . . . 284
Electric Brake Boost . . . . . . . . . . . . . . . . . . . . . . 246
Electric Parking Brake . . . . . . . . . . . . . . . . . . . . 247
Electric Parking Brake Light . . . . . . . . . . . . . . . 117
Electrical Equipment, Add-On . . . . . . . . . . . . .318
Electrical System
Engine Compartment Fuse Block . . . . . . . 353
Fuses and Circuit Breakers . . . . . . . . . . . . . 353
Instrument Panel Fuse Block . . . . . . 357, 358
Overload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
Electronic Stability Control (ESC) Off Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
Emergency
OnStar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441
Engine Air Cleaner/Filter . . . . . . . . . . . . . . . . . . . . . . 334
Check Light (Malfunction Indicator) . . . . . 115
Compartment Overview . . . . . . . . . . . . . . . . 325
Coolant Temperature Gauge . . . . . . . . . . . . 112
Coolant Temperature Warning Light . . . . 121
Cooling System . . . . . . . . . . . . . . . . . . . . . . . . 335
Drive Belt Routing . . . . . . . . . . . . . . . . . . . . . 427 Engine (cont'd)
Exhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
Oil Life System . . . . . . . . . . . . . . . . . . . . . . . . 332
Oil Pressure Gauge . . . . . . . . . . . . . . . . . . . . . 111
Oil Pressure Light . . . . . . . . . . . . . . . . . . . . . . 122
Overheated Protection
Operating Mode . . . . . . . . . . . . . . . . . . . . . 340
Overheating . . . . . . . . . . . . . . . . . . . . . . . . . . . 338
Power Messages . . . . . . . . . . . . . . . . . . . . . . . . 131
Running While Parked . . . . . . . . . . . . . . . . . 238
Starting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
Engine Air Filter Life System . . . . . . . . . . . . . 333
Entry Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
Equipment, Towing . . . . . . . . . . . . . . . . . . . . . . 296
Event Data Recorders . . . . . . . . . . . . . . . . . . . . 438
Exit Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
Extended Parking . . . . . . . . . . . . . . . . . . . . . . . . 238
Extender, Seat Belt . . . . . . . . . . . . . . . . . . . . . . . 59
Exterior Cargo Lamps . . . . . . . . . . . . . . . . . . . . 144
Exterior Lamp Controls . . . . . . . . . . . . . . . . . . . 139
Exterior Lamps Off Reminder . . . . . . . . . . . . . 141
Exterior Lighting Battery Saver . . . . . . . . . . .147

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./Cana-
da/Mexico-14632426) - 2021 - CRC - 11/5/20
Index 457
S
Safety Defects ReportingCanadian Government . . . . . . . . . . . . . . . . . 437
General Motors . . . . . . . . . . . . . . . . . . . . . . . . 437
U.S. Government . . . . . . . . . . . . . . . . . . . . . . . 436
Safety Locks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Safety System Check . . . . . . . . . . . . . . . . . . . . . 60
Satellite Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Scheduling Appointments . . . . . . . . . . . . . . . . 433
Seat Belts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Extender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
How to Wear Seat Belts Properly . . . . . . . 55
Lap-Shoulder Belt . . . . . . . . . . . . . . . . . . . . . . . 57
Reminders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Replacing after a Crash . . . . . . . . . . . . . . . . . 60
Use During Pregnancy . . . . . . . . . . . . . . . . . . 59
Seats Adjustment, Front . . . . . . . . . . . . . . . . . . . . . . 46
Center Seat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Head Restraints . . . . . . . . . . . . . . . . . . . . . . . . . 45
Heated and Ventilated Front . . . . . . . . . . . . 52
Heated, Rear . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Lumbar Adjustment, Front . . . . . . . . . . . . . . 48
Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Power Adjustment, Front . . . . . . . . . . . . . . . 47
Rear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Reclining Seatbacks . . . . . . . . . . . . . . . . . . . . . 48 Seats (cont'd)
Underseat Storage . . . . . . . . . . . . . . . . . . . . . . 96
Securing Child Restraints . . . . . . . . . . . . . . 88, 92
Security Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
OnStar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441
Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Vehicle Alarm . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 Accessories and Modifications . . . . . . . . . 323
Climate Control System . . . . . . . . . . . . . . . . 204
Doing Your Own Work . . . . . . . . . . . . . . . . . 323
Maintenance Records . . . . . . . . . . . . . . . . . . 422
Maintenance, General Information . . . . . 408
Parts Identification . . . . . . . . . . . . . . . . . . . . . 423
Scheduling Appointments . . . . . . . . . . . . . . 433
Service Electric Parking Brake Light . . . . . . . 118
Services Special Application . . . . . . . . . . . . . . . . . . . . . 415
Servicing System . . . . . . . . . . . . . . . . . . . . . . . . . 175
Servicing the Airbag . . . . . . . . . . . . . . . . . . . . . . 69
Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
Shift Lock Control Function Check, Automatic Transmission . . . . . . . . . . . . . . . . 347
Shifting Into Park . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
Out of Park . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
Side Blind Zone Alert (SBZA) . . . . . . . . . . . . . 280 Signals, Turn and Lane-Change . . . . . . . . . . . .143
Snow Plow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .318
Software Updates . . . . . . . . . . . . . . . . . . . . . . . . . 155
Special Application Services . . . . . . . . . . . . . . .415
Specifications and Capacities . . . . . . . . . . . . . 424
Speedometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
Start Assist, Hill . . . . . . . . . . . . . . . . . . . . . . . . . . 248
Start Vehicle, Remote . . . . . . . . . . . . . . . . . . . . . 20
Starter Switch Check . . . . . . . . . . . . . . . . . . . . . 347
Starting the Engine . . . . . . . . . . . . . . . . . . . . . . 232
Steering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .214
Heated Wheel . . . . . . . . . . . . . . . . . . . . . . . . . 100
Wheel Adjustment . . . . . . . . . . . . . . . . . . . . . 100
Wheel Controls . . . . . . . . . . . . . . . . . . . . . . . . 100
Steering Column Lock . . . . . . . . . . . . . . . . . . . . . .32
Steering Wheel Controls . . . . . . . . . . . . . . . . . . 151
Steps Power Assist . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Stop/Start System . . . . . . . . . . . . . . . . . . . . . . . 233
Stoplamps and Back-up Lamps Bulb Replacement . . . . . . . . . . . . . . . . . . . . . . 351
Storage Rear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
Storage Areas Center Console . . . . . . . . . . . . . . . . . . . . . . . . . 96
Floor Console . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Glove Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Underseat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96