2021 GMC YUKON ignition

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
Driving and Operating 237
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.
The settings are:
N (Neutral) :Use only when the vehicle
needs to be towed. See Recreational Vehicle
Towing 0371 or
Towing the Vehicle 0370.
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.
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.
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.
4
n(Four-Wheel Drive Low) : This setting
engages the front axle and delivers extra
torque. Choose 4
nwhen driving off-road in
deep sand, deep mud, or deep snow, and
while climbing or descending steep hills.
While driving in 4
n, keep vehicle speed
below 72 km/h (45 mph).
Shifting into 4
nwill turn Traction Control
and StabiliTrak/ESC off. See Traction Control/
Electronic Stability Control 0242.
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 to
indicate that the 4x4 transfer case has been
requested to shift to the new desired state. Once the 4x4 shift has completed, the DIC
message disappears, the 4x4 graphic stops
flashing, and the current setting is indicated.
When a shift to 2
mis completed successfully
while in P (Park), the parking brake will
engage. To resume driving, shift the
transmission to the desired gear and
manually release the parking brake or press
the accelerator pedal to begin driving. See
Electric Parking Brake 0240.
If equipped, use 4
n, AUTO, or 4mto provide
additional traction when parking on a steep
grade with poor traction such as ice, snow,
mud, or gravel.
Shifting Into 4
n
1. The ignition must be on and the vehicle must be stopped or moving less than
5 km/h (3 mph) with the transmission in
N (Neutral). It is best for the vehicle to
be moving 1.6 to 3.2 km/h (1 to 2 mph).
2. Press 4
n. 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 to indicate that
the 4x4 transfer case has been requested
to shift to the new desired state.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
238 Driving and Operating
Once the 4x4 shift has completed, the
DIC message disappears, the 4x4 graphic
stops flashing and the current setting is
indicated.
If vehicle speed is higher when shift request
occurs, a DIC message displays. Reduce
vehicle speed.
If the transmission is not in N (Neutral)
when shift request occurs, a DIC message
displays. The vehicle will allow 20 seconds
for the shift to occur. After this time, a
graphic in the instrument cluster will
indicate that the transfer case is in 4
n.
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 Out of 4
n
1. The vehicle must be stopped or moving
less than 5 km/h (3 mph) with the
transmission in N (Neutral) and the
ignition on. It is best for the vehicle to
be moving 1.6 to 3.2 km/h (1 to 2 mph).
2. Press 4
m, AUTO, or 2m. 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
to indicate the state of the request.
Once the 4x4 shift has completed, the
DIC message disappears, the 4x4 graphic
stops flashing, and the current setting is
indicated.
If vehicle speed is higher when shift
request occurs, a DIC message displays.
Reduce vehicle speed.
If the transmission is not in N (Neutral)
when shift request occurs, DIC messages will
display. The vehicle will allow 20 seconds for
this shift to occur. After this time, a graphic
in the instrument cluster will indicate that
the transfer case is in 4
n.
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.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
Driving and Operating 239
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 0226.
2. Set the parking brake. See Electric
Parking Brake 0240.
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.
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.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
Driving and Operating 241
Before leaving the vehicle, check the red
parking brake status light to ensure that the
parking brake is applied.
EPB Apply
To apply the EPB:1. Be sure the vehicle is at a complete stop.
2. Press the EPB switch momentarily.
The red parking brake status light will flash
and then stay on once the EPB is fully
applied. If the red parking brake status light
flashes continuously, then the EPB is only
partially applied or there is a problem with
the EPB. A DIC message will display. Release
the EPB and try to apply it again. If the
light does not come on, or keeps flashing,
have the vehicle serviced. Do not drive the
vehicle if the red parking brake status light
is flashing. See your dealer.
If the amber service parking brake warning
light is on, press the EPB switch. Continue to
hold the switch until the red parking brake
status light remains on. If the amber service
parking brake warning light is on, see your
dealer. If the EPB is applied while the vehicle is
moving, the vehicle will decelerate as long
as the switch is pressed. If the switch is
pressed until the vehicle comes to a stop,
the EPB will remain applied.
The vehicle may automatically apply the EPB
in some situations when the vehicle is not
moving. This is normal, and is done to
periodically check the correct operation of
the EPB system, or at the request of other
safety functions that utilize the EPB.
If the EPB fails to apply, block the rear
wheels to prevent vehicle movement.
EPB Release
To release the EPB:
1. Turn the ignition on or to ACC/ ACCESSORY.
2. Apply and hold the brake pedal.
3. Press the EPB switch momentarily.
The EPB is released when the red parking
brake status light is off.
If the amber service parking brake warning
light is on, release the EPB by pressing and
holding the EPB switch. Continue to hold the
switch until the red parking brake status
light is off. If either light stays on after
release is attempted, see your dealer.
Caution
Driving with the parking brake on can
overheat the brake system and cause
premature wear or damage to brake
system parts. Make sure that the parking
brake is fully released and the brake
warning light is off before driving.
If you are towing a trailer and parking on a
hill, see Driving Characteristics and Towing
Tips 0280.
Automatic EPB Release
The EPB will automatically release if the
vehicle is running, placed into gear, and an
attempt is made to drive away. Avoid rapid
acceleration when the EPB is applied, to
preserve parking brake lining life.
Brake Assist
Brake Assist detects rapid brake pedal
applications due to emergency braking
situations and provides additional braking to
activate the Antilock Brake System (ABS) if
the brake pedal is not pushed hard enough
to activate ABS normally. Minor noise, brake
pedal pulsation, and/or pedal movement
during this time may occur. Continue to

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
Driving and Operating 245
When enabled, if the vehicle speed is above
30 km/h (19 mph) and below 60 km/h
(37 mph), a DIC message will display.
Driver Mode Control
Driver Mode Control (DMC) allows the driver
to adjust the overall driving experience to
better suit preference by adjusting multiple
sub-system simultaneously. Drive Mode
availability and affected vehicle subsystems
are dependent upon vehicle trim level,
region, and optional features.
Normal Mode will be the default mode at
every ignition cycle. A unique and persistent
indicator will be displayed in the instrument
cluster for each mode.
Depending on trim level, Normal, Sport,
Snow/Ice, Off-Road, Tow/Haul, and Terrain
modes may be available.
To activate each mode, turn the Mode knob
on the instrument panel to the left of the
steering wheel.
To activate Terrain mode, press the Terrain
Mode button located next to the
Mode knob.
Normal Mode :Use for normal city and
highway driving to provide a smooth ride.
This setting provides balance between
comfort and handling. This is the standard/
default mode. There is no persistent
indicator in the instrument cluster for
this mode.
8Sport Mode : Use where road conditions
or personal preference demand a more
controlled response. 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 no
spirited driving is detected. The steering will
change to provide more precise control.
If the vehicle has Magnetic Ride Control, the
suspension will change to provide better
cornering performance.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
252 Driving and Operating
Resuming a Set Speed
If the cruise control is set at a desired speed
and then the brakes are applied or
*is
pressed, the cruise control is disengaged
without erasing the set speed from memory.
Once the vehicle reaches about 40 km/h
(25 mph) or more, press RES+ up briefly. The
vehicle returns to the previously set speed.
Increasing Speed While Using Cruise Control
Do one of the following:
.Press and hold +RES up until the desired
speed is reached, then release it.
.To increase vehicle speed in small
increments, press +RES up briefly. For
each press, the vehicle goes about 1 km/h
(1 mph) faster.
The speedometer reading can be displayed
in either English or metric units. See
Instrument Cluster 0104. The increment
value used depends on the units displayed.
Reducing Speed While Using Cruise Control
Do one of the following:
.Press and hold SET– down until the
desired lower speed is reached, then
release it.
.To slow down in small increments, press
SET– down briefly. For each press, the
vehicle goes about 1 km/h (1 mph) slower.
The speedometer reading can be displayed
in either English or metric units. See
Instrument Cluster 0104. The increment
value used depends on the units displayed.
Passing Another Vehicle While Using Cruise
Control
Use the accelerator pedal to increase the
vehicle speed. When you take your foot off
the pedal, the vehicle will slow down to the
previously set cruise speed. While pressing
the accelerator pedal or shortly following
the release to override cruise control, briefly
pressing SET– will result in cruise control set
to the current vehicle speed.
Using Cruise Control on Hills
How well the cruise control works on hills
depends on the vehicle speed, the load, and
the steepness of the hills. When going up
steep hills, pressing the accelerator pedal
may be necessary to maintain vehicle speed.
While going downhill, cruise braking helps
maintain driver selected speed. Cruise Grade Braking is enabled when the
vehicle is started and cruise control is active.
It is not enabled in Range Selection Mode.
It assists in maintaining driver selected
speed when driving on downhill grades by
using the engine and transmission to slow
the vehicle.
For other forms of descent control, see
Hill
Descent Control (HDC) 0244, Automatic
Transmission 0232, and Tow/Haul Mode
0 235.
Ending Cruise Control
There are four ways to end cruise control:
.Step lightly on the brake pedal.
.Press*.
.Shift the transmission to N (Neutral).
.To turn off cruise control, press5.
Erasing Speed Memory
The cruise control set speed is erased from
memory if
5is pressed or the ignition is
turned off.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
258 Driving and Operating
Irregular Objects Affecting ACC
ACC may have difficulty detecting the
following objects:
.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.
.Objects that are close to the front of your
vehicle.
ACC Automatically Disengages
ACC may automatically disengage and the
driver will need to manually apply the
brakes to slow the vehicle if:
.The sensors are blocked.
.The Traction Control System (TCS) or
StabiliTrak/ESC system has activated or
been disabled.
.There is a fault in the system.
.The radar falsely reports blockage when
driving in a desert or remote area with
no other vehicles or roadside objects.
A DIC message may display 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 0126.
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
driver seat belt is unbuckled, the ACC
automatically applies the Electric Parking
Brake (EPB) to hold the vehicle. The EPB
status light will turn on. See Electric Parking
Brake 0240. A DIC warning message may display
indicating to shift to P (Park) before exiting
the vehicle. See
Vehicle Messages 0125.
{Warning
If ACC has stopped the vehicle, and if ACC
is disengaged, turned off, or canceled, the
vehicle will no longer be held at a stop.
The vehicle can move. When ACC is
holding the vehicle at a stop, always be
prepared to manually apply the brakes.
{Warning
Leaving the vehicle without placing it in
P (Park) can be dangerous. Do not leave
the vehicle while it is being held at a
stop by ACC. Always place the vehicle in
P (Park) and turn off the ignition before
leaving the vehicle.
ACC Override
If using the accelerator pedal while ACC is
active, the ACC indicator turns blue on the
instrument cluster indicating ACC braking
will not occur. ACC will resume operation
when the accelerator pedal is not being
pressed.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
260 Driving and Operating
ACC will not detect a vehicle ahead until it
is completely in the lane. The brakes may
need to be manually applied.
Objects Not Directly in Front of Your Vehicle
The detection of objects in front of the
vehicle may not be possible if:
.The vehicle or object ahead is not within
your lane.
.The vehicle ahead is shifted, not centered,
or is shifted to one side of the lane.
Driving in Narrow Lanes
Vehicles in adjacent traffic lanes or roadside
objects may be incorrectly detected when
located along the roadway.
Do Not Use ACC on Hills and When Towing a
Trailer
Do not use ACC when driving on steep hills
or when towing a trailer. ACC will not detect
a vehicle in the lane while driving on steep
hills.
Disengaging ACC
There are three ways to disengage ACC:
.Step lightly on the brake pedal.
.Press*.
.PressJ.
Erasing Speed Memory
The ACC set speed is erased from memory if
Jis pressed or if the ignition is turned off.
Weather Conditions Affecting ACC
System operation may be limited under
snow, heavy rain, or road spray conditions.
Accessory Installations and Vehicle
Modifications
Do not install or place any object around
the front camera windshield area that would
obstruct the front camera view.
Do not install objects on top of the vehicle
that overhang and obstruct the front
camera, such as a canoe, kayak, or other
items that can be transported on a roof rack
system. See Roof Rack System 093. Do not modify the hood, headlamps, or fog
lamps, as this may limit the camera’s ability
to detect an object.
Cleaning the Sensing System
The camera sensor on the windshield behind
the rearview mirror, and the sensors on the
front of the vehicle can become blocked by
snow, ice, dirt, mud, or debris. This area
needs to be cleaned for ACC to operate
properly.
If ACC will not operate, regular cruise control
may be available. See
“Switching Between
ACC and Regular Cruise Control” previously
in this section. Always consider driving
conditions before using either cruise control
system.
For cleaning instructions, see “Washing the
Vehicle” underExterior Care 0374.
Driver Assistance Systems
This vehicle may have features that work
together to help avoid crashes or reduce
crash damage while driving, backing, and
parking. Read this entire section before
using these systems.