2021 GMC SIERRA door

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 229
Ignition Positions (Key Access)
0. Stopping the Engine/LOCK/OFF
1. ACC/ACCESSORY
2. ON/RUN
3. START
The ignition switch has four positions.
To shift out of P (Park), the ignition must be
ON/RUN and the brake pedal must be
applied.0 (Stopping the Engine/LOCK/OFF) :
This
position turns off the vehicle. It also locks
the ignition, the transmission, and the
steering column, if equipped with a locking
steering column.
To turn off the vehicle:
1. Make sure that the vehicle is stopped.
2. Shift to P (Park).
3. Continue to hold the brake pedal, then set the parking brake. See Electric
Parking Brake 0247.
4. Push the key all the way in toward the steering column, then turn the key to
LOCK/OFF. 5. Remove the key.
6. Release the brake pedal.
See your dealer if the key can be removed
in any other position.
Retained Accessory Power (RAP) will remain
active. See Retained Accessory Power (RAP)
0 236.
A warning chime will sound when the driver
door is opened and the key is in the
ignition.
If equipped with a locking steering column,
the steering can bind with the front wheels
turned off center, which may prevent key
rotation out of LOCK/OFF. If this happens,
move the steering wheel from right to left
while turning the key to ACC/ACCESSORY.
If this does not work, then the vehicle needs
service.
{Warning
Turning off the vehicle while moving may
cause loss of power assist in the brake
and steering systems and disable the
airbags. While driving, turn off the
vehicle only in an emergency.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
230 Driving and Operating
In an emergency, if the vehicle cannot be
pulled over and must be turned off while
driving:1. Push the key all the way in toward the steering column, then turn the key to
ACC/ACCESSORY.
2. Brake using firm and steady pressure. Do not pump the brakes repeatedly. This
may deplete power assist, requiring
increased brake pedal force.
3. Shift the vehicle to N (Neutral). This can be done while the vehicle is moving.
Continue braking and steer the vehicle to
a safe location.
4. Come to a complete stop.
5. Shift to P (Park).
6. Push the key all the way in toward the steering column (1), then turn the
ignition to LOCK/OFF (2).
7. Set the parking brake. See Electric
Parking Brake 0247.
8. Remove the key.
9. Release the brake pedal.Caution
Use the correct key, make sure it is all
the way in —or pushed all the way in
toward the steering column when turning
off the vehicle —and turn it only with
your hand.
1 (ACC/ACCESSORY) : This position allows
features such as the infotainment system to
operate while the vehicle is off. It also
unlocks the steering column, if equipped
with a locking steering column. Use this
position if the vehicle must be pushed or
towed. See Retained Accessory Power (RAP)
0 236.
From ON/RUN, push the key all the way in
toward the steering column, then turn the
key to ACC/ACCESSORY.
If the key is left in ACC/ACCESSORY with the
engine off, the battery could drain and the
vehicle may not start.
A warning chime will sound when the driver
door is opened and the key is in the
ignition.
2 (ON/RUN) : This position can be used to
operate the electrical accessories and to
display some instrument cluster warning
and indicator lights. This position can also be used for service and diagnostics, and to
verify the proper operation of the
malfunction indicator lamp as may be
required for emission inspection purposes.
The switch stays in this position when the
engine is running. The transmission is also
unlocked in this position.
If the key is left in ON/RUN with the engine
off, the battery could drain and the vehicle
may not start.
3 (START) :
This is the position that starts
the engine. When the engine starts, release
the key. The ignition returns to ON/RUN for
driving.
Ignition Positions (Keyless Access)

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 231
Vehicles equipped with Keyless Access have
pushbutton starting.
The Remote Keyless Entry (RKE) transmitter
must be in the vehicle for the system to
operate. If the pushbutton start is not
working, the vehicle may be near a strong
radio antenna signal causing interference to
the Keyless Access system. SeeRemote
Keyless Entry (RKE) System Operation (Key
Access) 010 or
Remote Keyless Entry (RKE) System
Operation (Keyless Access) 013.
To shift out of P (Park), the ignition must be
on or in Service Mode, and the brake pedal
must be applied.
{Warning
Turning off the vehicle while moving may
cause loss of power assist in the brake
and steering systems and disable the
airbags. While driving, only shut the
vehicle off in an emergency.
Stopping the Engine/LOCK/OFF (No Indicator
Lights) : When the vehicle is stopped, press
ENGINE START/STOP once to turn the
engine off. If the vehicle is in P (Park), the ignition will
turn off, and Retained Accessory Power (RAP)
will remain active. See
Retained Accessory
Power (RAP) 0236.
If the vehicle is not in P (Park), the ignition
will return to ACC/ACCESSORY and display
the message SHIFT TO PARK in the Driver
Information Center (DIC). When the vehicle is
shifted into P (Park), the ignition system will
turn off.
The vehicle may have an electric steering
column lock. The lock is activated when the
ignition is turned off and driver door is
opened. A sound may be heard as the lock
actuates or releases. The steering column
lock may not release with the wheels turned
off center. If this happens, the vehicle may
not start. Move the steering wheel from left
to right while attempting to start the
vehicle. If this does not work, the vehicle
needs service.
Unless an emergency exists, do not turn the
engine off when the vehicle is moving. This
will cause a loss of power assist in the brake
and steering systems and disable the
airbags. If the vehicle must be shut off in an
emergency:
1. If the vehicle cannot be pulled over, and must be shut off while driving, press and
hold ENGINE START/STOP button for
longer than two seconds, or press twice
in five seconds.
2. Brake using a firm and steady pressure. Do not pump the brakes repeatedly. This
may deplete power assist, requiring
increased brake pedal force.
3. Shift the vehicle to N (Neutral). This can be done while the vehicle is moving.
After shifting to N (Neutral), firmly apply
the brakes and steer the vehicle to a
safe location.
4. Come to a complete stop, shift to P (Park), and make sure engine is off.
The shift lever must be in P (Park) to
turn the ignition off.
5. Set the parking brake. See Electric
Parking Brake 0247.

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.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
236 Driving and Operating
Retained Accessory Power (RAP)
When the ignition is turned from on to off,
the following features (if equipped) will
continue to function for up to 10 minutes,
or until the driver door is opened. These
features will also work when the ignition is
in RUN or ACC/ACCESSORY:
.Infotainment System
.Power Windows (during RAP this
functionality will be lost when any door
is opened)
.Sunroof (during RAP this functionality will
be lost when any door is opened)
.Auxiliary Power Outlet
.Audio System
.OnStar System
Shifting Into Park
{Warning
It can be dangerous to get out of the
vehicle if the shift lever is not fully in
P (Park) with the parking brake firmly set.
The vehicle can roll. If you have left the
engine running, the vehicle can move
suddenly. You or others could be injured.(Continued)
Warning (Continued)
To be sure the vehicle will not move,
even when you are on fairly level ground,
use the steps that follow. With
four-wheel drive, if the transfer case is in
N (Neutral), the vehicle will be free to
roll, even if the shift lever is in P (Park).
Be sure the transfer case is in a drive
gear. If towing a trailer, seeDriving
Characteristics and Towing Tips 0288.
1. Hold the brake pedal down, then set the parking brake. See Electric Parking Brake
0 247.
2. Move the shift lever into the P (Park) position by pulling the shift lever toward
you and moving it up as far as it will go.
3. Be sure the transfer case (if equipped) is in a drive gear –not in N (Neutral).
4. Turn the ignition off. For Key Access, push the ignition key in, towards the
steering column and then turn the
ignition off.
5. For Key Access, remove the key and take it with you. If you can leave the vehicle
with the ignition key in your hand, the
vehicle is in P (Park). For Keyless Access, take the Remote
Keyless Entry (RKE) transmitter with you.Leaving the Vehicle with the Engine
Running
{Warning
It can be dangerous to leave the vehicle
with the engine running. The vehicle
could move suddenly if the shift lever is
not fully in P (Park) with the parking
brake firmly set.
If you have four-wheel drive and the
transfer case is in N (Neutral), the vehicle
will be free to roll, even if the shift lever
is in P (Park). So be sure the transfer case
is in a drive gear
–not in N (Neutral).
And, if you leave the vehicle with the
engine running, it could overheat and
even catch fire. You or others could be
injured. Do not leave the vehicle with the
engine running unless you have to.
If you have to leave the vehicle with the
engine running, be sure the vehicle is in
P (Park) and the parking brake is firmly set
before you leave it. After moving the shift
lever into P (Park), hold the regular brake

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
Driving and Operating 261
Stationary or Very Slow-Moving Objects
{Warning
ACC may not detect and react to stopped
or slow-moving vehicles ahead of you. For
example, the system may not brake for a
vehicle it has never detected moving. This
can occur in stop-and-go traffic or when a
vehicle suddenly appears due to a vehicle
ahead changing lanes. Your vehicle may
not stop and could cause a crash. Use
caution when using ACC. Your complete
attention is always required while driving
and you should be ready to take action
and apply the brakes.
Irregular Objects Affecting ACC
ACC may have difficulty detecting the
following objects:
.Vehicles in front of your vehicle that have
a rear aspect that is low, small,
or irregular
.An empty truck or trailer that has no
cargo in the cargo bed
.Vehicles with cargo extending from the
back end
.Non-standard shaped vehicles, such as
vehicle transport, vehicles with a side car
fitted, or horse carriages
.Vehicles that are low to the road surface
.Objects that are close to the front of your
vehicle
.Vehicles on which extremely heavy cargo
is loaded in the cargo area or rear seat
ACC Automatically Disengages
ACC may automatically disengage and the
driver will need to manually apply the
brakes to slow the vehicle if:
.The front camera is blocked or visibility is
reduced.
.The Traction Control System (TCS) or
StabiliTrak/ESC system has activated or
been disabled.
.There is a fault in the system.
.A DIC message displays to indicate that
ACC is temporarily unavailable.
The ACC indicator will turn white when ACC
is no longer active.
In some cases, when ACC is temporarily
unavailable, regular cruise control may be
used. See “Switching Between ACC and
Regular Cruise Control” previously in this
section. Always consider driving conditions
before using either cruise control system.
Notification to Resume ACC
ACC will maintain a follow gap behind a
detected vehicle and slow your vehicle to a
stop behind that vehicle.
If the stopped vehicle ahead has driven
away and ACC has not resumed, the vehicle
ahead indicator will flash as a reminder to
check traffic ahead before proceeding. In
addition, the left and right sides of the
Safety Alert Seat will pulse three times,
or three beeps will sound. See ”Alert Type”
and “Adaptive Cruise Go Notifier” in
“Collision/Detection Systems” underVehicle
Personalization 0131.
When the vehicle ahead drives away, press
RES+ or the accelerator pedal to resume
ACC. If stopped for more than two minutes
or if the driver door is opened and the

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 283
When the System Does Not Seem to
Work Properly
The system performance may be
affected by:
.Close vehicles ahead.
.Sudden lighting changes, such as when
driving through tunnels.
.Banked roads.
.Roads with poor lane markings, such as
two-lane roads.
If the LKA system is not functioning
properly when lane markings are clearly
visible, cleaning the windshield may help.
A camera blocked message may display if
the camera is blocked. Some driver
assistance systems may have reduced
performance or not work at all. An LKA or
LDW unavailable message may display if the
systems are temporarily unavailable. This
message could be due to a blocked camera.
The LKA system does not need service. Clean
the outside of the windshield behind the
rearview mirror.
LKA assistance and/or LDW alerts may occur
due to tar marks, shadows, cracks in the
road, temporary or construction lane
markings, or other road imperfections. This is normal system operation; the vehicle does
not need service. Turn LKA off if these
conditions continue.
Fuel
Top Tier Fuel
GM recommends the use of TOP TIER
Detergent Gasoline to keep the engine clean,
reduce engine deposits, and maintain
optimal vehicle performance. Look for the
TOP TIER Logo or see www.toptiergas.com
for a list of TOP TIER Detergent Gasoline
marketers and applicable countries.
Recommended Fuel (Except 6.2L
V8 Engine)
For diesel engine vehicles, see
“Fuel for
Diesel Engines” in the Duramax diesel
supplement.
If the vehicle has a yellow fuel cap or a
yellow sticker on the fuel door, E85 or
FlexFuel can be used. If the vehicle does not
have a yellow fuel cap or yellow sticker, do
not use gasoline with ethanol levels greater
than 15% by volume. See E85 or FlexFuel
0 284.
Use regular unleaded gasoline meeting
ASTM specification D4814 with a posted
octane rating of 87 —(R+M)/2 —or higher.
Do not use gasoline with a posted octane
rating of less than 87, as this may cause
engine knock and will lower fuel economy.