2021 GMC YUKON brake service mode

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
Seats and Restraints 65
least partially inflated for some time after
they inflate. Some components of the airbag
module may be hot for several minutes. For
location of the airbags, seeWhere Are the
Airbags? 062.
The parts of the airbag that come into
contact with you may be warm, but not too
hot to touch. There may be some smoke
and dust coming from the vents in the
deflated airbags. Airbag inflation does not
prevent the driver from seeing out of the
windshield or being able to steer the
vehicle, nor does it prevent people from
leaving the vehicle.
{Warning
When an airbag inflates, there may be
dust in the air. This dust could cause
breathing problems for people with a
history of asthma or other breathing
trouble. To avoid this, everyone in the
vehicle should get out as soon as it is
safe to do so. If you have breathing
problems but cannot get out of the
vehicle after an airbag inflates, then get
fresh air by opening a window or a door. (Continued)
Warning (Continued)
If you experience breathing problems
following an airbag deployment, you
should seek medical attention.
The vehicle has a feature that may
automatically unlock the doors, turn on the
interior lamps and hazard warning flashers,
and shut off the fuel system after the
airbags inflate. The feature may also
activate, without airbag inflation, after an
event that exceeds a predetermined
threshold. After turning the ignition off and
then on again, the fuel system will return to
normal operation; the doors can be locked,
the interior lamps can be turned off, and
the hazard warning flashers can be turned
off using the controls for those features.
If any of these systems are damaged in the
crash they may not operate as normal.
{Warning
A crash severe enough to inflate the
airbags may have also damaged
important functions in the vehicle, such
as the fuel system, brake and steering
systems, etc. Even if the vehicle appears (Continued)
Warning (Continued)
to be drivable after a moderate crash,
there may be concealed damage that
could make it difficult to safely operate
the vehicle.
Use caution if you should attempt to
restart the engine after a crash has
occurred.
In many crashes severe enough to inflate
the airbag, windshields are broken by
vehicle deformation. Additional windshield
breakage may also occur from the front
outboard passenger airbag.
.Airbags are designed to inflate only once.
After an airbag inflates, you will need
some new parts for the airbag system.
If you do not get them, the airbag
system will not be there to help protect
you in another crash. A new system will
include airbag modules and possibly other
parts. The service manual for the vehicle
covers the need to replace other parts.
.The vehicle has a crash sensing and
diagnostic module which records
information after a crash. See Vehicle
Data Recording and Privacy 0408 and
Event Data Recorders 0409.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
Instruments and Controls 95
Instruments and Controls
Controls
Steering Wheel Adjustment . . . . . . . . . . . . 96
Steering Wheel Controls . . . . . . . . . . . . . . . 96
Heated Steering Wheel . . . . . . . . . . . . . . . . . 96
Horn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Windshield Wiper/Washer . . . . . . . . . . . . . . 97
Rear Window Wiper/Washer . . . . . . . . . . . 98
Compass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Power Outlets . . . . . . . . . . . . . . . . . . . . . . . . . 100
Wireless Charging . . . . . . . . . . . . . . . . . . . . . 101
Warning Lights, Gauges, and Indicators
Warning Lights, Gauges, andIndicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Instrument Cluster . . . . . . . . . . . . . . . . . . . . 104
Speedometer . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Odometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Trip Odometer . . . . . . . . . . . . . . . . . . . . . . . . 106
Tachometer . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Fuel Gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Engine Oil Pressure Gauge . . . . . . . . . . . . . 107
Engine Coolant Temperature Gauge . . . 108
Voltmeter Gauge . . . . . . . . . . . . . . . . . . . . . . 108
Seat Belt Reminders . . . . . . . . . . . . . . . . . . . 109
Airbag Readiness Light . . . . . . . . . . . . . . . . 109
Passenger Airbag Status Indicator . . . . . . 110
Charging System Light . . . . . . . . . . . . . . . . . 111 Malfunction Indicator Lamp (Check
Engine Light) . . . . . . . . . . . . . . . . . . . . . . . . . 111
Brake System Warning Light . . . . . . . . . . . 112
Electric Parking Brake Light . . . . . . . . . . . . 113
Service Electric Parking Brake Light . . . . . 113
Antilock Brake System (ABS) Warning Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Four-Wheel-Drive Light . . . . . . . . . . . . . . . . . 114
Hill Descent Control Light . . . . . . . . . . . . . . 114
Lane Keep Assist (LKA) Light . . . . . . . . . . . 114
Vehicle Ahead Indicator . . . . . . . . . . . . . . . . 115
Pedestrian Ahead Indicator . . . . . . . . . . . . . 115
Traction Off Light . . . . . . . . . . . . . . . . . . . . . . 115
Traction Control System (TCS)/Electronic Stability Control Light . . . . . . . . . . . . . . . . 115
Electronic Stability Control (ESC) Off Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Engine Coolant Temperature Warning Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Driver Mode Control Light . . . . . . . . . . . . . 116
Four Corner Air Suspension Light . . . . . . . 117
Tire Pressure Light . . . . . . . . . . . . . . . . . . . . . 118
Engine Oil Pressure Light . . . . . . . . . . . . . . 118
Low Fuel Warning Light . . . . . . . . . . . . . . . . 118
Security Light . . . . . . . . . . . . . . . . . . . . . . . . . . 119
High-Beam On Light . . . . . . . . . . . . . . . . . . . 119
Front Fog Lamp Light . . . . . . . . . . . . . . . . . . 119
Lamps On Reminder . . . . . . . . . . . . . . . . . . . 119
Cruise Control Light . . . . . . . . . . . . . . . . . . . . 119
Door Ajar Light . . . . . . . . . . . . . . . . . . . . . . . . 120
Information Displays
Driver Information Center (DIC) . . . . . . . . 120
Head-Up Display (HUD) . . . . . . . . . . . . . . . . 122
Vehicle Messages
Vehicle Messages . . . . . . . . . . . . . . . . . . . . . . 125
Engine Power Messages . . . . . . . . . . . . . . . 125
Vehicle Speed Messages . . . . . . . . . . . . . . . 126
Vehicle Personalization
Vehicle Personalization . . . . . . . . . . . . . . . . 126
Universal Remote System
Universal Remote System . . . . . . . . . . . . . . 131
Universal Remote System Programming . . . . . . . . . . . . . . . . . . . . . . . . . 131
Universal Remote System Operation . . . 133

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
112 Instruments and Controls
If the light continues to flash, find a safe
place to park. Turn the vehicle off and wait
at least 10 seconds before restarting the
engine. If the light is still flashing, follow
the previous guidelines and see your dealer
for service as soon as possible.
If the light is on steady :A malfunction has
been detected. Diagnosis and service may be
required.
Check the following:
.If fuel has been added to the vehicle
using the capless fuel funnel adapter,
make sure that it has been removed. See
“Filling the Tank with a Portable Gas Can”
under Filling the Tank 0278. The
diagnostic system can detect if the
adapter has been left installed in the
vehicle, allowing fuel to evaporate into
the atmosphere. A few driving trips with
the adapter removed may turn off the
light.
.Poor fuel quality can cause inefficient
engine operation and poor driveability,
which may go away once the engine is
warmed up. If this occurs, change the fuel
brand. It may require at least one full
tank of the proper fuel to turn the light off. See
Recommended Fuel (5.3L Engine)
0 277 or
Recommended Fuel (6.2L Engine) 0277.
If the light remains on, see your dealer.
Emissions Inspection and Maintenance
Programs
If the vehicle requires an Emissions
Inspection/Maintenance test, the test
equipment will likely connect to the
vehicle's Data Link Connector (DLC).
The DLC is under the instrument panel to
the left of the steering wheel. Connecting
devices that are not used to perform an
Emissions Inspection/Maintenance test or to
service the vehicle may affect vehicle
operation. See Add-On Electrical Equipment
0 306. See your dealer if assistance is
needed.
The vehicle may not pass inspection if:
.The light is on when the engine is
running.
.The light does not come on when the
ignition is in Service Mode.
.Critical emission control systems have not
been completely diagnosed. If this
happens, the vehicle would not be ready
for inspection and might require
several days of routine driving before the
system is ready for inspection. This can
happen if the 12-volt battery has recently
been replaced or run down, or if the
vehicle has been recently serviced.
See your dealer if the vehicle will not pass
or cannot be made ready for the test.
Brake System Warning Light
MetricEnglish
This light should come on briefly when the
vehicle is turned on. If it does not come on
then, have it fixed so it will be ready to
warn you if there is a problem.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
114 Instruments and Controls
If the ABS warning light stays on, or comes
on again while driving, the vehicle needs
service. A chime may also sound when the
light stays on.
If the ABS warning light is the only light on,
the vehicle has regular brakes, but ABS is
not functioning.
If both the ABS warning light and the brake
system warning light are on, ABS is not
functioning and there is a problem with the
regular brakes. See your dealer for service.
SeeBrake System Warning Light 0112.
Four-Wheel-Drive Light
Auto Mode Shown, Other Modes Similar
If equipped, the four-wheel-drive light
displays what mode the vehicle is in. The
light will show each mode: 2WD, 4HI, AUTO
(all transfer cases); 4LOW and N (two-speed
transfer case only). The light will flash when a shift is in
progress. Once the shift is complete the
light will be steady.
If the light turns amber, there may be a
malfunction with the four-wheel-drive
system. See your dealer.
See
Four-Wheel Drive 0236.
Hill Descent Control Light
If equipped, the Hill Descent Control light
comes on when the system is ready for use.
When the light flashes, the system is active.
See Hill Descent Control (HDC) 0244.
Lane Keep Assist (LKA) Light
After the vehicle is started, this light turns
off and stays off if LKA has not been turned
on or is unavailable.
If equipped, this light is white if LKA is
turned on, but not ready to assist.
This light is green if LKA is turned on and is
ready to assist.
LKA may assist by gently turning the
steering wheel if the vehicle approaches a
detected lane marking. The LKA light is
amber when assisting.
This light flashes amber as a Lane Departure
Warning (LDW) alert, to indicate that the
lane marking has been crossed.
LKA will not assist or alert if the turn signal
is active in the direction of lane departure,
or if LKA detects that you are accelerating,
braking or actively steering.
See Lane Keep Assist (LKA) 0275.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
Driving and Operating 227
interference to the Keyless Access system.
SeeRemote Keyless Entry (RKE) System
Operation 08.
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) 0229.
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 either front 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.
If the vehicle must be shut off in an
emergency:
1. Brake using a firm and steady pressure. Do not pump the brakes repeatedly. This
may deplete power assist, requiring
increased brake pedal force.
2. 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.
3. Come to a complete stop. Hold the brake pedal down and shift to P (Park). The
vehicle must be in P (Park) to turn the
ignition off.
4. Continue to hold the brake pedal down. 5. Set the parking brake. See
Electric
Parking Brake 0240.
6. Press ENGINE START/STOP once to turn the ignition off.
7. Release the brake pedal.
If the vehicle cannot be pulled over, and
must be shut off while driving, press and
hold ENGINE START/STOP for longer than
two seconds, or press twice in five seconds.
ACC/ACCESSORY (Amber Indicator Light) :
This mode allows some electrical accessories
to be used when the engine is off.
With the ignition off, pressing the button
one time without the brake pedal applied
will place the ignition system in ACC/
ACCESSORY.
The ignition will switch from ACC/
ACCESSORY to off after five minutes to
prevent battery rundown.
ON/RUN/START (Green Indicator Light) : This
mode is for driving and starting. With the
ignition off, and the brake pedal applied,
pressing the button once will turn the
ignition on. Once engine cranking begins,
release the button. Engine cranking will
continue until the engine starts. See Starting
the Engine 0228.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
228 Driving and Operating
Service Mode
This power mode is available for service and
diagnostics, and to verify the proper
operation of the malfunction indicator lamp
as may be required for emission inspection
purposes. With the vehicle off, and the
brake pedal not applied, pressing and
holding the button for more than
five seconds will place the vehicle in Service
Mode. The instruments and audio systems
will operate as they do when the ignition is
on, but the vehicle will not be able to be
driven. The engine will not start in Service
Mode. Press the button again to turn the
ignition off.
Starting the Engine
If the vehicle has a diesel engine, see the
Duramax diesel supplement.
Caution
If you add electrical parts or accessories,
you could change the way the engine
operates. Any resulting damage would
not be covered by the vehicle warranty.
SeeAdd-On Electrical Equipment 0306. Shift the vehicle into P (Park) or N (Neutral).
To restart the engine when the vehicle is
already moving, use N (Neutral) only.
Caution
Do not try to shift to P (Park) if the
vehicle is moving. If you do, you could
damage the transmission. Shift to P (Park)
only when the vehicle is stopped.
Starting Procedure
1. The remote key must be in the vehicle.
Press ENGINE START/STOP with the brake
pedal applied. When the engine begins
cranking, let go of the button.
The idle speed will go down as the
engine gets warm. Do not race the
engine immediately after starting it.
Operate the engine and transmission
gently to allow the oil to warm up and
lubricate all moving parts.
When the low fuel warning light is on
and the FUEL LEVEL LOW message is
displayed in the Driver Information
Center (DIC), press the ENGINE START/
STOP position to continue engine
cranking.
Caution
Cranking the engine for long periods of
time, by trying to start the engine
immediately after cranking has ended,
can overheat and damage the cranking
motor, and drain the battery. Wait at
least 15 seconds between each try, to let
the cranking motor cool down.
2. If the engine does not start after five to 10 seconds, especially in very cold
weather (below −18 °C or 0 °F), it could
be flooded with too much gasoline. Try
pushing the accelerator pedal all the way
to the floor and holding it there while
pressing ENGINE START/STOP for up to a
maximum of 15 seconds. Wait at least
15 seconds between each try, to allow
the cranking motor to cool down. When
the engine starts, let go of the button
and accelerator. If the vehicle starts
briefly but then stops again, do the
same thing. This clears the extra gasoline
from the engine. Do not race the engine
immediately after starting it. Operate
the engine and transmission gently until
the oil warms up and lubricates all
moving parts.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
Driving and Operating 269
Following Distance Indicator
The following distance to a moving vehicle
ahead in your path is indicated in following
time in seconds on the Driver Information
Center (DIC). SeeDriver Information Center
(DIC) 0120. The minimum following time is
0.5 seconds away. If there is no vehicle
detected ahead, or the vehicle ahead is out
of sensor range, dashes will be displayed.
Unnecessary Alerts
FCA may provide unnecessary alerts for
turning vehicles, vehicles in other lanes,
objects that are not vehicles, or shadows.
These alerts are normal operation and the
vehicle does not need service.
Cleaning the System
If the FCA system does not seem to operate
properly, this may correct the issue:
.Clean the outside of the windshield in
front of the rearview mirror.
.Clean the entire front of the vehicle.
.Clean the headlamps.
For cleaning instructions, see “Washing the
Vehicle” underExterior Care 0374.
System operation may also be limited under
snow, heavy rain, or road spray conditions.
Automatic Emergency
Braking (AEB)
If the vehicle has Forward Collision Alert
(FCA), it also has AEB, which includes
Intelligent Brake Assist (IBA). When the
system detects a vehicle ahead in your path
that is traveling in the same direction that
you may be about to crash into, it can
provide a boost to braking or automatically
brake the vehicle. This can help avoid or
lessen the severity of crashes when driving
in a forward gear. Depending on the
situation, the vehicle may automatically
brake moderately or hard. This automatic
emergency braking can only occur if a
vehicle is detected. This is shown by the FCA
vehicle ahead indicator being lit. See
Forward Collision Alert (FCA) System 0267.
The system works when driving in a forward
gear between 8 km/h (5 mph) and 80 km/h
(50 mph), or on vehicles with Adaptive
Cruise Control (ACC), above 4 km/h (2 mph).
It can detect vehicles up to approximately
60 m (197 ft).
{Warning
AEB is an emergency crash preparation
feature and is not designed to avoid
crashes. Do not rely on AEB to brake the
vehicle. AEB will not brake outside of its
operating speed range and only responds
to detected vehicles.
AEB may not:
.Detect a vehicle ahead on winding or
hilly roads.
.Detect all vehicles, especially vehicles
with a trailer, tractors, muddy
vehicles, etc.
.Detect a vehicle when weather limits
visibility, such as in fog, rain, or snow.
.Detect a vehicle ahead if it is partially
blocked by pedestrians or other
objects.
Complete attention is always required
while driving, and you should be ready to
take action and apply the brakes and/or
steer the vehicle to avoid crashes.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
292 Driving and Operating
.White/Green: Back-up Lamps
.Red/Green: Battery Feed
.Dark Blue: Trailer Brake
To help charge a remote (non-vehicle)
battery change drive mode to Tow Haul.
If the trailer is too light for Tow/Haul Mode,
turn on the headlamps to help charge the
battery.
Electric Brake Control Wiring Provisions
These wiring provisions are included with
the vehicle as part of the trailer wiring
package. These provisions are for an electric
brake controller.
The harness should be installed by your
dealer or a qualified service center.
Refer to the aftermarket electric trailer brake
controller owner's manual to determine wire
color coding of the electric trailer brake
controller. The wire colors on the brake
controller may be different from the vehicle.
Trailer Lamps
Always check all trailer lamps are working at
the beginning of each trip, and periodically
on longer trips.
Turn Signals When Towing a Trailer
When properly connected, the trailer turn
signals should will illuminate to indicate the
vehicle is turning, changing lanes,
or stopping. When towing a trailer, the
arrows on the instrument cluster will
illuminate even if the trailer is not properly
connected or the bulbs are burned out.
Tow/Haul Mode
For instructions on how to enter Tow/Haul
mode, see Tow/Haul Mode 0235.
Tow/Haul assists when pulling a heavy
trailer or a large or heavy load.
Tow/Haul Mode is designed to be most
effective when the vehicle and trailer
combined weight is at least 75% of the
vehicle's Gross Combined Weight Rating
(GCWR). See “Maximum Trailer Weight”
under Trailer Towing 0284.
Tow/Haul Mode is most useful when towing
a heavy trailer or carrying a large or
heavy load:
.through rolling terrain
.in stop-and-go traffic
.in busy parking lots Operating the vehicle in Tow/Haul Mode
when lightly loaded or not towing will not
cause damage; however, it is not
recommended and may result in unpleasant
engine and transmission driving
characteristics and reduced fuel economy.
Integrated Trailer Brake Control System
The vehicle may have an Integrated Trailer
Brake Control (ITBC) system for use with
electric trailer brakes or most electric over
hydraulic trailer brake systems. These
instructions apply to both types of electric
trailer brakes.
This symbol is on the Trailer Brake Control
Panel on vehicles with an ITBC system. The
power output to the trailer brakes is
proportional to the amount of vehicle
braking. This available power output to the
trailer brakes can be adjusted to a wide
range of trailering situations.