2020 GMC SIERRA maintenance

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
ContentsIntroduction . . . . . . . . . . . . . . . . . . . . . . 2
Keys, Doors, and Windows . . . . . . 9
Seats and Restraints . . . . . . . . . . . 53
Storage . . . . . . . . . . . . . . . . . . . . . . . 113
Instruments and Controls . . . . . . 118
Lighting . . . . . . . . . . . . . . . . . . . . . . . 165
Infotainment System . . . . . . . . . . 176
Climate Controls . . . . . . . . . . . . . . 177
Driving and Operating . . . . . . . . . 185
Vehicle Care . . . . . . . . . . . . . . . . . . 327
Service and Maintenance . . . . . 440
Technical Data . . . . . . . . . . . . . . . . 458
Customer Information . . . . . . . . . 463
Reporting Safety Defects . . . . . . 473
OnStar . . . . . . . . . . . . . . . . . . . . . . . . 477
Connected Services . . . . . . . . . . . 485
Index . . . . . . . . . . . . . . . . . . . . 488

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
84 Seats and Restraints
of the seat fabric, could also
interfere with the operation of the
passenger sensing system. This
could either prevent proper
deployment of the passenger
airbag(s) or prevent the passenger
sensing system from properly
turning off the passenger airbag(s).
SeePassenger Sensing System
0 78.
If the vehicle has rollover roof-rail
airbags, see Different Size Tires
and Wheels 0401 for additional
important information.
If a snow plow is added to the
vehicle, the airbags should still work
properly. The airbag systems were
designed to work properly under a
wide range of conditions, including
snow plowing with vehicles that
have the optional snow plow prep
package (RPO VYU). Do not
change or defeat the snow plow's
“tripping mechanism.” If you do, it
can damage the snow plow and the
vehicle, and may cause an airbag
deployment. If the vehicle must be modified
because you have a disability and
have questions about whether the
modifications will affect the vehicle's
airbag system, or if you have
questions about whether the airbag
system will be affected if the vehicle
is modified for any other reason, call
Customer Assistance. See
Customer Assistance Offices
0465.
Airbag System Check
The airbag system does not need
regularly scheduled maintenance or
replacement. Make sure the airbag
readiness light is working. See
Airbag Readiness Light 0136.
Caution
If an airbag covering is damaged,
opened, or broken, the airbag
may not work properly. Do not
open or break the airbag
coverings. If there are any
opened or broken airbag
coverings, have the airbag
(Continued)
Caution (Continued)
covering and/or airbag module
replaced. For the location of the
airbags, seeWhere Are the
Airbags? 074. See your dealer
for service.
Replacing Airbag System
Parts after a Crash
{Warning
A crash can damage the airbag
systems in the vehicle.
A damaged airbag system may
not properly protect you and your
passenger(s) in a crash, resulting
in serious injury or even death. To
help make sure the airbag
systems are working properly
after a crash, have them
inspected and any necessary
replacements made as soon as
possible.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
134 Instruments and Controls
Uplevel English Shown, BaseLevel and Midlevel Similar
The engine oil pressure gauge
shows the engine oil pressure
in kPa (kilopascals) or psi (pounds
per square inch) when the engine is
running.
Oil pressure can vary with engine
speed, outside temperature, coolant
temperature, and oil viscosity.
On some models, the oil pump will
vary engine oil pressure according
to engine needs. Oil pressure may
change quickly as the engine speed
or load varies. This is normal. If the
oil pressure warning light or Driver Information Center (DIC) message
indicates oil pressure outside the
normal operating range, check the
vehicle's oil as soon as possible.
See
Engine Oil 0339.
Caution
Lack of proper engine oil
maintenance can damage the
engine. Driving with the engine oil
low can also damage the engine.
The repairs would not be covered
by the vehicle warranty. Check
the oil level as soon as possible.
Add oil if required, but if the oil
level is within the operating range
and the oil pressure is still low,
have the vehicle serviced. Always
follow the maintenance schedule
for changing engine oil.
If the vehicle has a diesel engine,
see the Duramax diesel
supplement.
Engine Coolant
Temperature Gauge
Uplevel Metric Shown, Base Level and Midlevel Similar

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Instruments and Controls 139
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
0329.
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.
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 funnel
adapter, make sure that it has
been removed. See “Filling the
Tank with a Portable Gas Can”
under Filling the Tank (Pickup
Model) 0283 or
Filling the Tank (Chassis Cab
Model) 0285. 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 (Except
6.2L V8 Engine) 0280 or
Recommended Fuel (6.2L
V8 Engine) 0281.
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).

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
140 Instruments and Controls
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. SeeAdd-On
Electrical Equipment 0322. 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 on while the
engine is off.
. 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.
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.
If equipped with 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 Vehicle
0424.
{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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
146 Instruments and Controls
For vehicles with the Tire Pressure
Monitor System (TPMS), this light
comes on briefly when the engine is
started. It provides information
about tire pressures and the TPMS.
When the Light Is On Steady
This indicates that one or more of
the tires are significantly
underinflated.
A Driver Information Center (DIC)
tire pressure message may also
display. Stop as soon as possible,
and inflate the tires to the pressure
value shown on the Tire and
Loading Information label. SeeTire
Pressure 0387.
When the Light Flashes First and
Then Is On Steady
If the light flashes for about a minute
and then stays on, there may be a
problem with the TPMS. If the
problem is not corrected, the light
will come on at every ignition cycle.
See Tire Pressure Monitor
Operation 0390.Engine Oil Pressure Light
(Uplevel Cluster)
Caution
Lack of proper engine oil
maintenance can damage the
engine. Driving with the engine oil
low can also damage the engine.
The repairs would not be covered
by the vehicle warranty. Check
the oil level as soon as possible.
Add oil if required, but if the oil
level is within the operating range
and the oil pressure is still low,
have the vehicle serviced. Always
follow the maintenance schedule
for changing engine oil.
This light should come on briefly as
the engine is started. If it does not
come on, have the vehicle serviced
by your dealer.
If the light comes on and stays on, it
means that oil is not flowing through
the engine properly. The vehicle
could be low on oil and might have
some other system problem. See
your dealer.
Low Fuel Warning Light
This light is near the fuel gauge and
comes on briefly when the ignition is
turned on as a check to show it is
working.
It also comes on when the fuel tank
is low on fuel. The light turns off
when fuel is added. If it does not,
have the vehicle serviced.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Instruments and Controls 149
recent driving history and the
amount of fuel remaining in the fuel
tank. Fuel range cannot be reset.
Tire Pressure
Turn the trip odometer reset stem
until a vehicle with the approximate
pressures of all four tires displays.
Tire pressure is displayed in either
kilopascal (kPa) or in pounds per
square inch (psi).
SeeTire Pressure Monitor System
0 389 and
Tire Pressure Monitor Operation
0 390.
Remaining Oil Life
Turn the trip odometer reset stem
until REMAINING OIL LIFE
displays. An estimate of the oil's
remaining useful life is shown.
REMAINING OIL LIFE 99% means
99% of the current oil life remains.
When the remaining oil life is low,
the CHANGE ENGINE OIL SOON
message will appear on the display.
The oil should be changed as soon
as possible. See Engine Oil0339.
In addition to the engine oil life system monitoring the oil life,
additional maintenance is
recommended. See
Maintenance
Schedule 0442.
The Oil Life display must be reset
after each oil change. It will not
reset itself. Do not reset the Oil Life
display at any time other than when
the oil has just been changed.
It cannot be reset accurately until
the next oil change. To reset the
engine oil life system, see Engine
Oil Life System 0341.
Air Filter Life
Turn the trip odometer reset stem
until AIR FILTER LIFE displays.
This displays an estimate of the
engine air filter ’s remaining useful
life and the state of the system.
Engine Air Filter Life 95% means
95% of the current air filter life
remains. Messages will display
based on the engine air filter life and
the state of the system.
When the REPLACE AT NEXT OIL
CHANGE message displays, the
engine air filter should be replaced
at the time of the next oil change. When the REPLACE SOON
message displays, the engine air
filter should be replaced at the
earliest convenience.
The Air Filter Life display must be
reset after the engine air filter
replacement. To reset, see
Engine
Air Filter Life System 0343.
Brake Pad Life
This displays an estimate of the
remaining life of the front and rear
brake pads. Messages will display
based on brake pad wear and the
state of the system. Reset the Brake
Pad Life display after replacing the
brake pads. See Brake Pad Life
System 0356.
Driver Information Center
(DIC) (Midlevel and
Uplevel)
The DIC displays are shown in the
center of the instrument cluster in
the Info app. See Instrument Cluster
0 127. The displays show the status
of many vehicle systems.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Instruments and Controls 151
economy that the vehicle has right
now, and will change as driving
conditions change.
Press the thumbwheel while this
display is active to reset the trip
odometer and the average fuel
economy.
Fuel Range :Shows the
approximate distance the vehicle
can be driven without refueling.
LOW will be displayed when the
vehicle is low on fuel. The fuel
range estimate is based on an
average of the vehicle's fuel
economy over recent driving history
and the amount of fuel remaining in
the fuel tank.
Timer : This display can be used as
a timer. To start the timer, press the
thumbwheel while this display is
active. The display will show the
amount of time that has passed
since the timer was last reset. To
stop the timer, press the
thumbwheel briefly while this display
is active and the timer is running.
Press the thumbwheel while this
display is active to reset the timer. Oil Life :
Shows an estimate of the
oil's remaining useful life.
If REMAINING OIL LIFE 99% is
displayed, that means 99% of the
current oil life remains.
When the remaining oil life is low,
the CHANGE ENGINE OIL SOON
message will appear on the display.
The oil should be changed as soon
as possible. See Engine Oil0339.
In addition to the engine oil life
system monitoring the oil life,
additional maintenance is
recommended. See Maintenance
Schedule 0442.
The Oil Life display must be reset
after each oil change. It will not
reset itself. Do not reset the Oil Life
display at any time other than when
the oil has just been changed.
It cannot be reset accurately until
the next oil change. To reset the
engine oil life system, press the
thumbwheel while the Oil Life
display is active. See Engine Oil
Life System 0341.
Tire Pressure : Shows the
approximate pressures of all four
tires. Tire pressure is displayed in either kilopascal (kPa) or in pounds
per square inch (psi). If the pressure
is low, the value for that tire is
shown in amber. See
Tire Pressure
Monitor System 0389 and
Tire Pressure Monitor Operation
0 390.
Air Filter Life : Shows an estimate
of the engine air filter ’s remaining
useful life and the state of the
system. Engine Air Filter Life 95%
means 95% of the current air filter
life remains. Messages will display
based on the engine air filter life and
the state of the system. When the
REPLACE AT NEXT OIL CHANGE
message displays, the engine air
filter should be replaced at the time
of the next oil change. When the
REPLACE SOON message
displays, the engine air filter should
be replaced at the earliest
convenience.
The Air Filter Life display must be
reset after the engine air filter
replacement. To reset, see Engine
Air Filter Life System 0343.