2021 GMC SIERRA four wheel drive

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 245
Caution
Shifting the transmission into gear before
the requested mode indicator light has
stopped flashing could damage the
transfer case.
If the transmission is not shifted into
N (Neutral) or the vehicle has not slowed to
5 km/h (3 mph) within 20 seconds, the
transfer case will remain in its original state.
This will be indicated in the instrument
cluster.
With the vehicle moving less than 5 km/h
(3 mph), and the transmission in N (Neutral),
attempt the shift again.
Shifting Into N (Neutral)
To shift into N (Neutral): 1. Start the vehicle.
2. Shift the transmission to N (Neutral).
3. Shift the transfer case to 2
m.
4. Apply the parking brake and/or brake pedal.
5. Press 2
mfive times in 10 seconds until
the N (Neutral) graphic starts flashing in
the instrument cluster. When the shift is
complete, the graphic stops flashing. If the parking brake and/or brake pedal
is not applied within 20 seconds, the
transfer case will remain in the original
state.
6. If the transmission is not shifted into N (Neutral) or the vehicle has not slowed
to 5 km/h (3 mph) within 20 seconds,
the transfer case will remain in its
original state. This will be indicated in
the instrument cluster.
Shifting Out of N (Neutral)
To shift out of N (Neutral): 1. Turn the ignition on with the engine off. See Ignition Positions (Keyless Access)
0 230 or
Ignition Positions (Key Access) 0229.
2. Set the parking brake. See Electric
Parking Brake 0247.
3. Shift the transmission to N (Neutral).
4. Shift the transfer case to 2
m. Transfer
case shifts out of N (Neutral) can only be
made into 2
m. When the shift to 2mis
complete, the graphic in the instrument
cluster will stop flashing. If the transfer
case cannot complete a shift, the graphic
will return to the previously selected
setting. Single Speed Transfer Case
If equipped, the transfer case controls are
used to shift into and out of four-wheel
drive.
To shift the transfer case, press the desired
button. The graphic in the instrument
cluster will flash while a shift is in progress.
The graphic displayed will change to indicate
the setting requested.
When the shift is complete the graphic will
stop flashing. The DIC message turns off
once the shift is complete. If the transfer
case cannot complete a shift request, it will
go back to its last chosen setting.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
246 Driving and Operating
The settings are:
2
m(Two-Wheel Drive High) :Use for driving
on most streets and highways. The front
axle is not engaged. This setting provides
the best fuel economy.
4
m(Four-Wheel Drive High) : Use this
setting when extra traction is needed, such
as when driving on snowy or icy roads,
when off-roading, or when plowing snow.
AUTO (Automatic Four-Wheel Drive)
Use when road surface conditions are
variable. When driving in AUTO, the front
axle is engaged, and the vehicle's power is
sent to the front and rear wheels
automatically based on driving conditions.
This setting provides slightly lower fuel
economy than 2
m.
Shifts between 2
m, 4m, and AUTO
Any of these shifts can be made at normal
driving speed.
The actual 4x4 shift request is only made
after the button is released. The 4x4 graphic
will remain flashing until the shift request
has completed. A DIC message displays. Once the 4x4 shift has completed, the DIC
message disappears, the 4x4 graphic stops
flashing, and the current setting is indicated.
The actual 4x4 shift request is only made
after the button is released. The 4x4 graphic
will remain flashing until the shift request
has completed.
A DIC message displays. Once the 4x4 shift
has completed, the DIC message disappears,
the 4x4 graphic stops flashing, and the
current setting is indicated.
Brakes
Electric Brake Boost
Vehicles equipped with electric brake boost
have hydraulic brake circuits that are
electronically controlled when the brake
pedal is applied during normal operation.
The system performs routine tests and turns
off within a few minutes after the vehicle is
turned off. Noise may be heard during this
time. If the brake pedal is pressed during
the tests or when the electric brake boost
system is off, a noticeable change in pedal
force and travel may be felt. This is normal.
Antilock Brake System (ABS)
The Antilock Brake System (ABS) helps
prevent a braking skid and maintain steering
while braking hard.
ABS performs a system check when the
vehicle is first driven. A momentary motor
or clicking noise may be heard while this
test is going on, and the brake pedal may
move slightly. This is normal.
If there is a problem with ABS, this warning
light stays on. See
Antilock Brake System
(ABS) Warning Light 0118.
ABS does not change the time needed to
get a foot on the brake pedal and does not
always decrease stopping distance. If you
get too close to the vehicle ahead, there will
not be enough time to apply the brakes if
that vehicle suddenly slows or stops. Always
leave enough room ahead to stop, even
with ABS.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 249
TCS activates if it senses any of the drive
wheels are spinning or beginning to lose
traction. When this happens, TCS applies the
brakes to the spinning wheels and reduces
engine power to limit wheel spin.
StabiliTrak/ESC activates when the vehicle
senses a difference between the intended
path and the direction the vehicle is actually
traveling. StabiliTrak/ESC selectively applies
braking pressure to any one of the vehicle
wheel brakes to assist the driver in keeping
the vehicle on the intended path. Trailer
Sway Control (TSC) is also on automatically
when the vehicle is started. SeeTrailer Sway
Control (TSC) 0306.
If cruise control is being used and traction
control or StabiliTrak/ESC begins to limit
wheel spin, cruise control will disengage.
Cruise control may be turned back on when
road conditions allow.
Both systems come on automatically when
the vehicle is started and begins to move.
The systems may be heard or felt while
they are operating or while performing
diagnostic checks. This is normal and does
not mean there is a problem with the
vehicle. It is recommended to leave both systems on
for normal driving conditions, but it may be
necessary to turn TCS off if the vehicle gets
stuck in sand, mud, ice, or snow. See
If the
Vehicle Is Stuck 0221 and “Turning the
Systems Off and On” later in this section.
When the transfer case (if equipped) is in
Four-Wheel Drive Low, the stability system
is automatically disabled,
gcomes on, and
the appropriate message will appear on the
Driver Information Center (DIC). Both
traction control and StabiliTrak/ESC are
automatically disabled in this condition.
The indicator light for both systems is in the
instrument cluster. This light will:
.Flash when TCS is limiting wheel spin.
.Flash when StabiliTrak/ESC is activated.
.Turn on and stay on when either system
is not working.
If either system fails to turn on or to
activate, a message displays in the Driver
Information Center (DIC), and
dcomes on and stays on to indicate that the system is
inactive and is not assisting the driver in
maintaining control. The vehicle is safe to
drive, but driving should be adjusted
accordingly.
If
dcomes on and stays on:
1. Stop the vehicle.
2. Turn the engine off and wait 15 seconds.
3. Start the engine.
Drive the vehicle. If
dcomes on and stays
on, the vehicle may need more time to
diagnose the problem. If the condition
persists, see your dealer.
Turning the Systems Off and On
The button for TCS and StabiliTrak/ESC is on
the center stack.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
250 Driving and Operating
Caution
Do not repeatedly brake or accelerate
heavily when TCS is off. The vehicle
driveline could be damaged.
To turn off only TCS, press and release
g.
The traction off light
idisplays in the
instrument cluster. The appropriate message
will display in the DIC. To turn TCS on again,
press and release
g. The traction off light
idisplayed in the instrument cluster will
turn off.
If TCS is limiting wheel spin when
gis
pressed, the system will not turn off until
the wheels stop spinning.
To turn off both TCS and StabiliTrak/ESC,
press and hold
guntil the traction off light
iand the StabiliTrak/ESC OFF lightgcome on and stay on in the instrument
cluster, then release. The appropriate
message will display in the DIC.
To turn TCS and StabiliTrak/ESC on again,
press and release
g. The traction off light
iand the StabiliTrak/ESC OFF lightgin
the instrument cluster turn off. StabiliTrak/ESC will automatically turn on if
the vehicle exceeds 56 km/h (35 mph).
Traction control will remain off.
The vehicle has a Trailer Sway Control (TSC)
feature and a Hill Start Assist (HSA) feature.
See
Trailer Sway Control (TSC) 0306 or
Hill Start Assist (HSA) 0248.
Adding accessories can affect the vehicle
performance. See Accessories and
Modifications 0323.
Hill Descent Control (HDC)
If equipped, Hill Descent Control (HDC) sets
and maintains vehicle speed while driving
down steep grades in a forward or reverse
gear. The HDC switch is on the center stack,
below the climate controls.
Press
5to enable or disable HDC. Vehicle
speed must be below 50 km/h (31 mph).
When enabled, the HDC light displays on
the instrument cluster. A blinking HDC light indicates the system is
actively applying the brakes to maintain
vehicle speed. HDC can maintain vehicle
speeds between 1 and 22 km/h (1 and
14 mph) on grades greater than or equal
to 10%.
If HDC is to be used for more than
three minutes or on grades steeper than
25%, the transfer case should be put into
Four-Wheel Drive Low (4
n) to reduce the
possibility of brake overheating.
Noise from the Electronic Brake Control
Module (EBCM) is normal when HDC is
active.
When HDC is activated, the initial HDC
speed is set to the current driving speed.
It can be increased or decreased by pressing
+RES or SET- on the steering wheel, or by
applying the accelerator or brake pedal. This
adjusted speed becomes the new set speed.
HDC will remain enabled between 30 and
60 km/h (19 and 37 mph); however, vehicle
speed cannot be set or maintained in this
range. HDC will automatically disable if the
vehicle speed is above 80 km/h (50 mph) or
above 60 km/h (37 mph) for at least
30 seconds.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
252 Driving and Operating
When you enter this mode, you will
immediately feel a down shift. In this mode
the vehicle also monitors driving behaviors
and automatically enables Performance Shift
Features when spirited driving is detected.
These features maintain lower transmission
gears to increase available engine braking
and improve acceleration response. The
vehicle will exit these features and return to
normal operation after a short period when
spirited driving is no longer detected. If the
vehicle has Magnetic Ride Control, the
suspension will change to provide better
cornering performance.
6Snow/Ice Mode :Snow/Ice Mode
improves vehicle acceleration on snow and
ice covered roads. When active, Snow/Ice
Mode will adjust acceleration to optimize
traction on slippery surfaces. This can
compromise the acceleration on dry asphalt.
This feature is not intended for use when
the vehicle is stuck in sand, mud, ice, snow,
or gravel. If the vehicle becomes stuck, see If
the Vehicle Is Stuck 0221.
7Off-Road Mode : Use this mode for
off-road recreational driving. Off-Road Mode
should be used to improve driving at
moderate speeds, on grass, gravel, dirt,
unpaved roads, or snow-covered roads. The accelerator pedal is tuned for off-road use.
This mode modifies pedal mapping,
All-Wheel Drive (AWD), ride height, Antilock
Brake System (ABS), StabiliTrak/Electronic
Stability Control (ESC), and Traction Control
System (TCS) performance.
For more information on off-road driving see
Off-Road Driving
0215.
_Tow/Haul Mode : Use this mode
when hauling heavy loads to provide
increased performance and vehicle control.
Tow/Haul Mode adjusts the transmission
shift pattern, AWD, and ESC performance.
If the vehicle is turned off with Tow/Haul
Mode active and then restarted within four
hours or less, Tow/Haul will remain active.
Otherwise, the vehicle will start in
Normal Mode.
If the vehicle has a diesel engine, exhaust
braking is automatically activated when
Tow/Haul Mode is selected. It maintains
vehicle speed by automatically
implementing a shift pattern that uses the
engine and the transmission to slow the
vehicle. The system will command
downshifts and use the turbocharger on the
engine to reduce vehicle speed when the
brake is applied. The normal tow/haul shift pattern will return once the vehicle is on a
low grade or when the accelerator pedal is
pressed.
While in the Electronic Range Select (ERS)
Mode (see
“manual mode”), grade breaking
is deactivated, allowing the driver to select a
range and limiting the highest gear
available.
For more information on trailer weight
specifications, see Towing Equipment 0296.
gTerrain Mode : Use for finer control
during low speed, off-road driving. When
using this mode it will mimic the
characteristics of four-wheel-drive low (4
n)
without the torque capabilities.
Use when:
.Traveling on very rough roads at very low
speeds, such as a two-track or heavily
rutted road.
.Traveling slowly in grassy fields.
.Pulling a boat out of the water on a
trailer.
.Using the vehicle for public off-road
recreational driving. See Off-Road Driving
0 215 and
Hill and Mountain Roads 0219.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 253
When in Terrain Mode, the vehicle will shift
automatically but may hold a lower gear
longer to maximize engine torque. The
steering will change to provide more precise
control. A unique pedal map, transmission
shift pattern, and rpm control are utilized to
give better control at lower speeds and over
rough terrain. When the vehicle comes to a
stop, Vehicle Hold is engaged. TCS will be
optimized for maximum torque transfer
across axles, and Active Braking During Lift
Throttle will be engaged.
Active Braking During Lift Throttle:
.Automatically applies light braking,
similar to heavy engine braking of
four-wheel-drive low.
.Applies light braking in D (Drive) until the
vehicle is at idle speeds. In Manual L1 and
Manual L2, moderate braking may stop
the vehicle.
.Reduces trailer braking.Terrain Mode Drive
Select Expected Vehicle Behavior Ideal Terrain
Drive (L3-Lx) Minor deceleration when off
throttle and mild ability to
modulate throttle; mimics
performance of 4
nwithout torque
multiplication. Grassy fields,
mild two tracks,
rutted roads,
large rolling hills,
L2 Moderate deceleration when off
throttle and moderate ability to
modulate throttle; will bring vehicle
to a stop in most cases. Mild rock crawling,
heavy ruts,
short, steeper grades,
L1 Significant deceleration when off
throttle and significant ability to
modulate throttle; will bring vehicle
to a stop in most cases. Rock crawling downhill
Active Braking During Lift Throttle will
reduce the back and forth between the
accelerator and brake pedals.
Vehicle Hold Features:
.When the vehicle comes to a stop on an
incline grade in forward gear or on a
decline grade in reverse gear, Vehicle
Hold is engaged until the accelerator
pedal is pressed.
.When the vehicle is in forward gear on a
decline, the vehicle is allowed to creep
down the hill when the brake pedal is
released without pressing the accelerator
pedal. The vehicle will also creep forward
on flat ground.
.If the driver seat belt is removed and the
driver door is opened while the vehicle is
being held, EPB will be engaged.
.EPB will engage if the vehicle is held for
an extended period.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
292 Driving and Operating
Warning (Continued)
.Do not move the vehicle if someone is
in the path of the trailer. Some parts
of the trailer might be underwater and
not visible to people who are assisting
in launching the boat.
Disconnect the wiring to the trailer before
backing the trailer into the water to prevent
damage to the electrical circuits on the
trailer. Reconnect the wiring to the trailer
after removing the trailer from the water.
If the trailer has electric brakes that can
function when the trailer is submerged, it
might help to leave the electrical trailer
connector attached to maintain trailer brake
functionality while on the boat ramp.
To back the trailer into the water: 1. If equipped, place the vehicle in four-wheel-drive high.
2. Slowly back down the boat ramp until the boat is floating, but no further than
necessary.
3. Press and hold the brake pedal, but do not shift into P (Park) yet.
4. Have someone place chocks under the front wheels of the vehicle. 5. Gradually release the brake pedal to
allow the chocks to absorb the load of
the trailer.
6. Reapply the brake pedal. Then apply the parking brake and shift into P (Park).
7. Release the brake pedal.
Pulling the Trailer from the Water
To pull the trailer out of the water: 1. Press and hold the brake pedal.
2. Start the engine and shift into gear.
3. Release the parking brake.
4. Let up on the brake pedal.
5. Drive slowly until the tires are clear of the chocks.
6. Stop and have someone pick up and store the chocks.
7. Slowly pull the trailer from the water.
8. Once the vehicle and trailer have been driven from the sloped part of the boat
ramp, the vehicle can be shifted from
four-wheel-drive high. Shift into the drive
mode that is appropriate for the road
conditions.
Caution
If the vehicle tires begin to spin and the
vehicle begins to slide toward the water,
remove your foot from the accelerator
pedal and apply the brake pedal. Seek
help to have the vehicle towed up
the ramp.
Maintenance when Trailer Towing
The vehicle needs service more often when
used to tow trailers. See Maintenance
Schedule 0409. It is especially important to
check the engine oil, axle lubricant, belts,
cooling system, and brake system before
and during each trip.
Check periodically to see that all nuts and
bolts on the trailer hitch are tight.
Engine Cooling When Trailer Towing
The cooling system may temporarily
overheat during severe operating conditions.
See Engine Overheating 0338.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Vehicle Care 321
Vehicle Care
General Information
General Information . . . . . . . . . . . . . . . . . . . 322
California Proposition 65 Warning . . . . . 322
California Perchlorate MaterialsRequirements . . . . . . . . . . . . . . . . . . . . . . . . 322
Accessories and Modifications . . . . . . . . . 323
Vehicle Checks
Doing Your Own Service Work . . . . . . . . . 323
Hood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
Engine Compartment Overview . . . . . . . . 325
Engine Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
Engine Oil Life System . . . . . . . . . . . . . . . . . 332
Automatic Transmission Fluid . . . . . . . . . . 333
Engine Air Filter Life System . . . . . . . . . . . 333
Engine Air Cleaner/Filter . . . . . . . . . . . . . . . 334
Cooling System . . . . . . . . . . . . . . . . . . . . . . . . 335
Engine Overheating . . . . . . . . . . . . . . . . . . . 338
Overheated Engine Protection Operating Mode . . . . . . . . . . . . . . . . . . . . . 340
Engine Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
Washer Fluid . . . . . . . . . . . . . . . . . . . . . . . . . . 340
Brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
Brake Pad Life System . . . . . . . . . . . . . . . . . 342
Brake Fluid . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
Battery - North America . . . . . . . . . . . . . . . 343 Four-Wheel Drive . . . . . . . . . . . . . . . . . . . . . . 346
Front Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
Rear Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
Starter Switch Check . . . . . . . . . . . . . . . . . . 347
Automatic Transmission Shift Lock
Control Function Check . . . . . . . . . . . . . . 347
Ignition Transmission Lock Check . . . . . . 347
Park Brake and P (Park) Mechanism Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347
Wiper Blade Replacement . . . . . . . . . . . . . 348
Glass Replacement . . . . . . . . . . . . . . . . . . . . 348
Windshield Replacement . . . . . . . . . . . . . . 348
Gas Strut(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
Headlamp Aiming
Front Headlamp Aiming . . . . . . . . . . . . . . . 350
Bulb Replacement
Bulb Replacement . . . . . . . . . . . . . . . . . . . . . 350
Halogen Bulbs . . . . . . . . . . . . . . . . . . . . . . . . . 350
LED Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . 350
Headlamps, Front Turn Signal, Sidemarker, and Parking Lamps . . . . . . 350
Taillamps, Turn Signal, Stoplamps, and Back-Up Lamps . . . . . . . . . . . . . . . . . . . . . . . 351
Center High-Mounted Stoplamp (CHMSL) and Cargo Lamp . . . . . . . . . . . . 352
License Plate Lamp . . . . . . . . . . . . . . . . . . . . 352
Electrical System
Electrical System Overload . . . . . . . . . . . . . 352
Fuses and Circuit Breakers . . . . . . . . . . . . . 353
Engine Compartment Fuse Block . . . . . . . 353
Instrument Panel Fuse Block (Left) . . . . . 357
Instrument Panel Fuse Block (Right) . . . 358
Wheels and Tires
Tires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360
All-Season Tires . . . . . . . . . . . . . . . . . . . . . . . . 361
Winter Tires . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
All-Terrain Tires . . . . . . . . . . . . . . . . . . . . . . . 362
Tire Sidewall Labeling . . . . . . . . . . . . . . . . . 362
Tire Designations . . . . . . . . . . . . . . . . . . . . . . 364
Tire Terminology and Definitions . . . . . . 365
Tire Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . 367
Tire Pressure Monitor System . . . . . . . . . 368
Tire Pressure Monitor Operation . . . . . . 369
Tire Inspection . . . . . . . . . . . . . . . . . . . . . . . . . 373
Tire Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . 374
When It Is Time for New Tires . . . . . . . . 375
Buying New Tires . . . . . . . . . . . . . . . . . . . . . 376
Different Size Tires and Wheels . . . . . . . . 377
Uniform Tire Quality Grading . . . . . . . . . . 377
Wheel Alignment and Tire Balance . . . . 378
Wheel Replacement . . . . . . . . . . . . . . . . . . . 378
Tire Chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
If a Tire Goes Flat . . . . . . . . . . . . . . . . . . . . . 380
Tire Changing . . . . . . . . . . . . . . . . . . . . . . . . . . 381
Full-Size Spare Tire . . . . . . . . . . . . . . . . . . . . 390