2021 GMC YUKON Owner's Manual

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
110 Instruments and Controls
pretensioners, the airbag modules, the
wiring, and the crash sensing and diagnostic
module. For more information on the airbag
system, seeAirbag System 060.
The airbag readiness light comes on for
several seconds when the vehicle is started.
If the light does not come on then, have it
fixed immediately.
{Warning
If the airbag readiness light stays on
after the vehicle is started or comes on
while driving, it means the airbag system
might not be working properly. The
airbags in the vehicle might not inflate in
a crash, or they could even inflate
without a crash. To help avoid injury,
have the vehicle serviced right away.
If there is a problem with the airbag
system, a Driver Information Center (DIC)
message may also come on.
Passenger Airbag Status Indicator
The vehicle has a passenger sensing system.
See Passenger Sensing System 066 for
important safety information. The overhead
console has a passenger airbag status
indicator.
United States and Canada
When the vehicle is started, the passenger
airbag status indicator will light ON and OFF,
and the symbols for on and off, for several
seconds as a system check. Then, after
several more seconds, the status indicator
will light either ON or OFF, and the symbol
for on or off, to let you know the status of
the front outboard passenger frontal airbag.
If the word ON, and the on symbol, are lit
on the passenger airbag status indicator, it
means that the front outboard passenger
frontal airbag is allowed to inflate. If the word OFF, and the off symbol, are lit
on the passenger airbag status indicator, it
means that the passenger sensing system
has turned off the front outboard passenger
frontal airbag.
If, after several seconds, both status
indicator lights remain on, if there are no
lights at all, or if the airbag readiness light
is on, there may be a problem with the
lights or the passenger sensing system. See
your dealer for service right away.{Warning
If the airbag readiness light ever comes
on and stays on, it means that
something may be wrong with the airbag
system. To help avoid injury to yourself
or others, have the vehicle serviced right
away. See
Airbag Readiness Light 0109
for more information, including important
safety information.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
Instruments and Controls 111
Charging System Light
The charging system light comes on briefly
when the ignition is turned on, but the
engine is not running, as a check to show
the light is working. It should go out when
the engine is started.
If the light stays on, or comes on while
driving, there may be a problem with the
electrical charging system. Have it checked
by your dealer. Driving while this light is on
could drain the battery.
When this light comes on, or is flashing, the
Driver Information Center (DIC) also displays
a message.
If a short distance must be driven with the
light on, be sure to turn off all accessories,
such as the radio and air conditioner.
Malfunction Indicator Lamp
(Check Engine Light)
This light is part of the vehicle’s emission
control on-board diagnostic system. If this
light is on while the engine is running, a
malfunction has been detected and the
vehicle may require service. The light should
come on to show that it is working when
the ignition is in Service Mode. SeeIgnition
Positions 0226.
Malfunctions are often indicated by the
system before any problem is noticeable.
Being aware of the light and seeking service
promptly when it comes on may prevent
damage.
Caution
If the vehicle is driven continually with
this light on, the emission control system
may not work as well, the fuel economy
may be lower, and the vehicle may not
(Continued)
Caution (Continued)
run smoothly. This could lead to costly
repairs that might not be covered by the
vehicle warranty.
Caution
Modifications to the engine, transmission,
exhaust, intake, or fuel system, or the
use of replacement tires that do not
meet the original tire specifications, can
cause this light to come on. This could
lead to costly repairs not covered by the
vehicle warranty. This could also affect
the vehicle’s ability to pass an Emissions
Inspection/Maintenance test. See
Accessories and Modifications 0309.
If the light is flashing : A malfunction has
been detected that could damage the
emission control system and increase vehicle
emissions. Diagnosis and service may be
required.
To help prevent damage, reduce vehicle
speed and avoid hard accelerations and
uphill grades. If towing a trailer, reduce the
amount of cargo being hauled as soon as
possible.

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
Instruments and Controls 113
If the light comes on and stays on at start
up, there is a brake problem. Have the brake
system inspected right away.
If the light comes on while driving, pull off
the road and stop carefully. The brake
system has electric brake boost. Vehicle
speed may be limited when the brake
system warning light comes on. The brake
pedal might be harder to push, or the brake
pedal may go closer to the floor. It could
take longer to stop. If the light is still on,
have the vehicle towed for service. See
Towing the Vehicle0370.
{Warning
The brake system might not be working
properly if the brake system warning
light is on. Driving with the brake system
warning light on can lead to a crash.
If the light is still on after the vehicle has
been pulled off the road and carefully
stopped, have the vehicle towed for
service.
Electric Parking Brake Light
MetricEnglish
This light comes on when the parking brake
is applied. If the light continues flashing
after the parking brake is released, or while
driving, there is a problem with the Electric
Parking Brake system. A message may also
display in the Driver Information
Center (DIC).
If the light does not come on, or remains
flashing, see your dealer.
Service Electric Parking Brake
Light
This light should come on briefly when
starting the vehicle. If it does not come on,
have it fixed so it will be ready to warn if
there is a problem.
If this light stays on, take the vehicle to
your dealer as soon as possible. See the
information for the Electric Parking Brake
under Electric Parking Brake 0240.
A message may also display in the Driver
Information Center (DIC).
Antilock Brake System (ABS)
Warning Light
This warning light should come on briefly
when the vehicle is turned on. If the light
does not come on, have it fixed so it will be
ready to warn if there is a problem.
If the light comes on while driving, safely
stop as soon as it is possible and turn off
the vehicle. Then turn on the vehicle again
to reset the system.

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
Instruments and Controls 115
Vehicle Ahead Indicator
If equipped, this indicator will display green
when a vehicle is detected ahead and amber
when you are following a vehicle ahead
much too closely.
SeeForward Collision Alert (FCA) System
0 267.
Pedestrian Ahead Indicator
If equipped, this indicator will display amber
when a nearby pedestrian is detected in
front of the vehicle.
See Front Pedestrian Braking (FPB) System
0 270.
Traction Off Light
This light comes on briefly while starting
the engine. If it does not, have the vehicle
serviced by your dealer. If the system is
working normally, the indicator light then
turns off.
The traction off light comes on when the
Traction Control System (TCS) has been
turned off by pressing and releasing the
TCS/StabiliTrak/ESC button.
This light and the StabiliTrak/ESC OFF light
come on when StabiliTrak/Electronic Stability
Control (ESC) is turned off.
If the TCS is off, wheel spin is not limited.
Adjust driving accordingly.
See Traction Control/Electronic Stability
Control 0242.
Traction Control System (TCS)/
Electronic Stability Control Light
If equipped, the Electronic Stability Control
(ESC) or TCS indicator/warning light comes
on briefly when the engine is started.
If the light does not come on, have the
vehicle serviced by your dealer. If the
system is working normally, the indicator
light turns off.
If the light is on and not flashing, the TCS,
and potentially the ESC system have been
disabled.
If the indicator/warning light is on and
flashing, the TCS and/or the ESC system is
actively working.
See Traction Control/Electronic Stability
Control 0242.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
116 Instruments and Controls
Trailer Sway Control Light
This light will flash when Trailer Sway
Control is active. SeeTrailer Sway Control
(TSC) 0295.
Electronic Stability Control (ESC)
Off Light
This light comes on briefly while starting
the engine. If it does not, have the vehicle
serviced by your dealer.
This light comes on when the ESC system is
turned off. If ESC is off, the Traction Control
System (TCS) is also off. If the ESC and TCS are off, the system does
not assist in controlling the vehicle. Turn on
the TCS and the ESC systems and the
warning light turns off.
See
Traction Control/Electronic Stability
Control 0242.
Engine Coolant Temperature
Warning Light
This light comes on briefly while starting
the vehicle.
If it does not, have the vehicle serviced by
your dealer. If the system is working
normally the indicator light goes off.
Caution
The engine coolant temperature warning
light indicates that the vehicle has
overheated. Driving with this light on can
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Caution (Continued)
damage the engine and it may not be
covered by the vehicle warranty. See
Engine Overheating 0322.
The engine coolant temperature warning
light comes on when the engine has
overheated.
If this happens, pull over and turn off the
engine as soon as possible. See Engine
Overheating 0322.
Driver Mode Control Light
This light comes on when Sport Mode is
selected.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-13690468) - 2021 - crc - 8/14/20
Instruments and Controls 117
This light comes on when Snow Mode is
selected.
This light comes on when Terrain Mode is
selected.
This light comes on when Off-Road Mode is
selected.
This light comes on when the Tow/Haul
Mode is selected.
Four Corner Air Suspension Light
This light comes on when the air suspension
is raised to maximum ground clearance
height.
This light comes on when the air suspension
is raised to increased ground clearance
height.
It will flash green and give an alert to
indicate that the vehicle is changing to a
higher ride height.
This light comes on when the air suspension
is lowered for easy entry and exit from the
vehicle.
It will flash green and give an alert to
indicate that the vehicle is changing to a
lower ride height.
This light comes on when the air suspension
is in Service Mode or Alignment Mode.
SeeFour Corner Air Suspension System
0 248.