service GMC SIERRA DENALI 2020 Manual PDF

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 353
vehicle to be driven to a safe place
in an emergency. Driving extended
distances and/or towing a trailer in
the overheat protection mode
should be avoided.
If the engine or transmission detects
an impending hot fluid condition,
then the transmission may force
upshifts to limit temperatures.
Downshifts may also be prevented
in this instance. Normal operation
may continue unless the display
indicates there is a hot condition
and engine should be idled.
Caution
After driving in the overheated
engine protection operating
mode, the engine oil will be
severely degraded. Any repairs
performed before the engine is
cool may cause engine damage.
Allow the engine to cool before
attempting any repair. Repair the
cause of coolant loss, change the
oil, and reset the oil life system.
SeeEngine Oil 0339.
Engine Fan
If the vehicle has the Duramax
diesel engine, see the Duramax
diesel supplement.
All Engines Except 6.6L
V8 Engine (L8T)
The vehicle has electric cooling
fan(s). The fans may be heard
spinning at low speed during most
everyday driving. The fans may turn
off if no cooling is required. Under
heavy vehicle loading, trailer towing,
high outside temperatures,
or operation of the air conditioning
system, the fans may change to
high speed and an increase in fan
noise may be heard. This is normal
and indicates that the cooling
system is functioning properly. The
fans will change to low speed when
additional cooling is no longer
required.
The electric engine cooling fans
may run after the engine has been
turned off. This is normal and no
service is required.
6.6L V8 Engine (L8T) Only
The vehicle has a clutched engine
cooling fan. When the clutch is
engaged, the fan spins faster to
provide more air to cool the engine.
In most everyday driving conditions,
the fan is spinning slower and the
clutch is not fully engaged. This
improves fuel economy and reduces
fan noise. Under heavy vehicle
loading, trailer towing, and/or high
outside temperatures, the fan speed
increases as the clutch more fully
engages, so an increase in fan
noise may be heard. This is normal
and should not be mistaken as the
transmission slipping or making
extra shifts. It is merely the cooling
system functioning properly. The fan
will slow down when additional
cooling is not required and the
clutch partially disengages.
This fan noise may be heard when
starting the engine. It will go away
as the fan clutch partially
disengages.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 355
Adding Washer Fluid
The vehicle has a low washer fluid
message on the DIC that comes on
when the washer fluid is low. The
message is displayed for
15 seconds at the start of each
ignition cycle. When the WASHER
FLUID LOW ADD FLUID message
displays, washer fluid will need to
be added to the windshield washer
fluid reservoir.
Open the cap with the washer
symbol on it. Add washer fluid until
the tank is full. SeeEngine
Compartment Overview 0332 for
reservoir location.
Caution
. Do not use washer fluid that
contains any type of water
repellent coating. This can
cause the wiper blades to
chatter or skip.
. Do not use engine coolant
(antifreeze) in the
windshield washer. It can
damage the windshield
washer system and paint.
. Do not mix water with
ready-to-use washer fluid.
Water can cause the
solution to freeze and
damage the washer fluid
tank and other parts of the
washer system.
. When using concentrated
washer fluid, follow the
manufacturer instructions for
adding water.
. Fill the washer fluid tank
only three-quarters full when
it is very cold. This allows
(Continued)
Caution (Continued)
for fluid expansion if
freezing occurs, which could
damage the tank if it is
completely full.
Brakes
Disc brake pads have built-in wear
indicators that make a high-pitched
warning sound when the brake pads
are worn and new pads are needed.
The sound can come and go or be
heard all the time the vehicle is
moving, except when applying the
brake pedal firmly.
{Warning
The brake wear warning sound
means that soon the brakes will
not work well. That could lead to
a crash. When the brake wear
warning sound is heard, have the
vehicle serviced.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
356 Vehicle Care
Caution
Continuing to drive with worn-out
brake pads could result in costly
brake repair.
Some driving conditions or climates
can cause a brake squeal when the
brakes are first applied or lightly
applied. This does not mean
something is wrong with the brakes.
Properly torqued wheel nuts are
necessary to help prevent brake
pulsation. When tires are rotated,
inspect brake pads for wear and
evenly tighten wheel nuts in the
proper sequence to torque
specifications in Capacities and
Specifications 0458.
Brake linings should always be
replaced as complete axle sets.
Brake Pedal Travel
See your dealer if the brake pedal
does not return to normal height,
or if there is a rapid increase in
pedal travel. This could be a sign
that brake service may be required.
Replacing Brake System Parts
Always replace brake system parts
with new, approved replacement
parts. If this is not done, the brakes
may not work properly. The braking
performance expected can change
in many other ways if the wrong
replacement brake parts are
installed or parts are improperly
installed.
Brake Pad Life System
When to Change Brake Pads
This vehicle has a system that
estimates the remaining life of the
front and rear brake pads. Brake
pad life is displayed in the Driver
Information Center (DIC), along with
a percentage for each axle. The
system must be reset every time the
brake pads are changed.
When the system has determined
that the brake pads need to be
replaced, a message will display,
which may include mileage
remaining. Brake pads should always be
replaced as complete axle sets.
How to Reset the Brake Pad
Life System
The system will automatically detect
when significantly worn brake pads
are replaced. When the ignition is
turned on after new pads and wear
sensors are installed, a message
will display. Follow the prompts to
reset the system.
The brake pad life system can also
be manually reset:
1. Display Brake Pad Life on the DIC. See Driver Information
Center (DIC) (Base Level)
0 147 or
Driver Information Center (DIC)
(Midlevel and Uplevel) 0148.
2. Press the thumbwheel or the trip odometer reset stem if the
vehicle does not have DIC
buttons. Select front or rear
pads as appropriate.
3. Select YES on the confirmation message, or press the trip
odometer reset stem on a base

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 361
For vehicles equipped with the Stop/
Start system:1. Install the negative battery cable to the battery
sensor stud.
2. Install the negative battery cable nut to the battery sensor
stud and tighten.
3. Turn the ignition on.
For vehicles not equipped with the
Stop/Start system: 1. Install the negative battery cable clamp to the negative
battery post.
2. Tighten the negative battery cable nut.
3. Turn the ignition on.
Four-Wheel Drive
Transfer Case
When to Check Lubricant
Refer to Maintenance Schedule
0 441 to determine when to check
the lubricant.
1. Fill Plug
2. Drain Plug
To get an accurate reading, the
vehicle should be on a level
surface.
If the level is below the bottom of
the fill plug (1) hole, located on the
transfer case, some lubricant will
need to be added. Add enough
lubricant to raise the level to the
bottom of the fill plug (1) hole. Use
care not to overtighten the plug. When to Change Lubricant
Refer to
Maintenance Schedule
0 441 to determine how often to
change the lubricant.
What to Use
Refer to Recommended Fluids and
Lubricants 0452 to determine what
kind of lubricant to use.
Front Axle
When to Check Lubricant
It is not necessary to regularly
check the front axle fluid unless a
leak is suspected or an unusual
noise is heard. A fluid loss could
indicate a problem. Have it
inspected and repaired. This service
can be complex. See your dealer.
Do not directly power wash the
transfer case and/or front/rear axle
output seals. High pressure water
can overcome the seals and
contaminate the fluid. Contaminated
fluid will decrease the life of the
transfer case and/or drive axles and
should be replaced.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
362 Vehicle Care
Rear Axle
When to Check Lubricant
It is not necessary to regularly
check the rear axle fluid unless a
leak is suspected or an unusual
noise is heard. A fluid loss could
indicate a problem. Have it
inspected and repaired. This service
can be complex. See your dealer.
Do not directly power wash the
transfer case and/or front/rear axle
output seals. High pressure water
can overcome the seals and
contaminate the fluid. Contaminated
fluid will decrease the life of the
transfer case and/or drive axles and
should be replaced.
Noise Control System
NOISE EMISSIONS
WARRANTY
General Motors LLC, warrants to the
first person who purchases this
vehicle for purposes other than
resale and to each subsequent
purchaser that this vehicle as
manufactured by General MotorsLLC, was designed, built and
equipped to conform at the time it
left General Motors LLC’s control
with all applicable U.S. EPA Noise
Control Regulations. This warranty
covers this vehicle as designed,
built and equipped by General
Motors LLC, and is not limited to
any particular part, component or
system of the vehicle manufactured
by General Motors LLC. Defects in
design, assembly or in any part,
component or system of the vehicle
as manufactured by General Motors
LLC, which, at the time it left
General Motors LLC’
s control,
caused noise emissions to exceed
Federal standards, are covered by
this warranty for the life of the
vehicle.
TAMPERING WITH NOISE
CONTROL SYSTEM
PROHIBITED
Federal law prohibits the following
acts or the causing thereof:
1. The removal or rendering inoperative by any person,
other than for purposes of maintenance, repair,
or replacement, of any device
or element of design
incorporated into any new
vehicle for the purpose of noise
control prior to its sale or
delivery to the ultimate
purchaser or while it is in
use; or
2. the use of the vehicle after such device or element of
design has been removed or
rendered inoperative by any
person.
Among those acts presumed to
constitute tampering are the acts
listed below.
Insulation:
Removal of the noise shields or any
undercab insulation.
Engine:
Removal or rendering engine speed
governor, if so equipped, inoperative
so as to allow engine speed to
exceed manufacturer specifications.
Modification of the engine control
system or calibration.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 363
Fan and Drive:
.Removal of fan clutch or
rendering clutch inoperative.
. Removal of the fan shroud.
Air Intake:
. Removal of air cleaner silencer.
. Reversing air cleaner cover.
Exhaust:
. Removal of muffler, catalytic
converter, and/or resonator.
. Removal of exhaust pipes and
exhaust pipe clamps.
Starter Switch Check
{Warning
When you are doing this
inspection, the vehicle could
move suddenly. If the vehicle
moves, you or others could be
injured. 1. Before starting this check, be
sure there is enough room
around the vehicle.
2. Apply both the parking brake and the regular brake.
Do not use the accelerator
pedal, and be ready to turn off
the engine immediately if it
starts.
3. Try to start the engine in each gear. The vehicle should start
only in P (Park) or N (Neutral).
If the vehicle starts in any other
position, contact your dealer for
service.
Automatic Transmission
Shift Lock Control
Function Check
{Warning
When you are doing this
inspection, the vehicle could
move suddenly. If the vehicle
moves, you or others could be
injured. 1. Before starting this check, be
sure there is enough room
around the vehicle. It should be
parked on a level surface.
2. Apply the parking brake. Be ready to apply the regular
brake immediately if the vehicle
begins to move.
3. With the engine off, turn the ignition on, but do not start the
engine. Without applying the
regular brake, try to move the
shift lever out of P (Park) with
normal effort. If the shift lever
moves out of P (Park), contact
your dealer for service.
Ignition Transmission
Lock Check
If equipped with Key Access
ignition, while parked, and with the
parking brake set, try to turn the
ignition off in each shift lever
position. The ignition should turn to
off only when the shift lever is in
P (Park).

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
364 Vehicle Care
The ignition key should come out
only when the ignition is off. Contact
your dealer if service is required.
Park Brake and P (Park)
Mechanism Check
{Warning
When you are doing this check,
the vehicle could begin to move.
You or others could be injured
and property could be damaged.
Make sure there is room in front
of the vehicle in case it begins to
roll. Be ready to apply the regular
brake at once should the vehicle
begin to move.
Park on a fairly steep hill, with the
vehicle facing downhill. Keeping
your foot on the regular brake, set
the parking brake.
. To check the parking brake's
holding ability: With the engine
running and the transmission in
N (Neutral), slowly remove foot pressure from the regular brake
pedal. Do this until the vehicle is
held by the parking brake only.
. To check the P (Park)
mechanism's holding ability:
With the engine running, shift to
P (Park). Then release the
parking brake followed by the
regular brake.
Contact your dealer if service is
required.
Wiper Blade Replacement
Windshield wiper blades should be
replaced periodically. See
Maintenance Schedule 0441.
Replacement blades come in
different types and are removed in
different ways. For proper type and
length, see Maintenance
Replacement Parts 0454.
Caution
Allowing the wiper arm to touch
the windshield when no wiper
blade is installed could damage
the windshield. Any damage that
occurs would not be covered by
the vehicle warranty. Do not allow
the wiper arm to touch the
windshield.
Front Wiper Blade
Replacement
To replace the wiper blade:
1. Pull the wiper assembly away from the windshield.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 365
2. Lift up on the latch in themiddle of the wiper blade
where the wiper arm attaches.
3. With the latch open, pull the wiper blade down toward the
windshield far enough to
release it from the J-hooked
end of the wiper arm.
4. Remove the wiper blade.
5. Reverse Steps 1–3 for wiper blade replacement.
Windshield Replacement
HUD System
The windshield is part of the HUD
system. If the windshield must be
replaced, get one that is designed
for HUD or the HUD image may
look out of focus.
Driver Assistance Systems
If the windshield needs to be
replaced and the vehicle is
equipped with a front camera sensor
for the Driver Assistance Systems, a
GM replacement windshield is
recommended. The replacement
windshield must be installed
according to GM specifications for
proper alignment. If it is not, these
systems may not work properly, they
may display messages, or they may
not work at all. See your dealer for
proper windshield replacement.
Gas Strut(s)
This vehicle is equipped with gas
strut(s) to provide assistance in
lifting and holding open the hood/
trunk/liftgate system in full open
position.
{Warning
If the gas struts that hold open
the hood, trunk, and/or liftgate fail,
you or others could be seriously
injured. Take the vehicle to your
dealer for service immediately.
Visually inspect the gas struts for
signs of wear, cracks, or other
damage periodically. Check to
make sure the hood/trunk/liftgate
is held open with enough force.
If struts are failing to hold the
hood/trunk/liftgate, do not
operate. Have the vehicle
serviced.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
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Vehicle Care 379
Wheels and Tires
Tires
Every new GM vehicle has
high-quality tires made by a
leading tire manufacturer. See
the warranty manual for
information regarding the tire
warranty and where to get
service. For additional
information refer to the tire
manufacturer.
{Warning
.Poorly maintained and
improperly used tires are
dangerous.
.Overloading the tires can
cause overheating as a
result of too much
flexing. There could be a
blowout and a serious
crash. SeeVehicle Load
Limits 0200.
(Continued)
Warning (Continued)
.Underinflated tires pose
the same danger as
overloaded tires. The
resulting crash could
cause serious injury.
Check all tires frequently
to maintain the
recommended pressure.
Tire pressure should be
checked when the tires
are cold.
.Overinflated tires are
more likely to be cut,
punctured, or broken by
a sudden impact —such
as when hitting a pothole.
Keep tires at the
recommended pressure.
.Worn or old tires can
cause a crash. If the
tread is badly worn,
replace them.
(Continued)
Warning (Continued)
.Replace any tires that
have been damaged by
impacts with potholes,
curbs, etc.
.Improperly repaired tires
can cause a crash. Only
the dealer or an
authorized tire service
center should repair,
replace, dismount, and
mount the tires.
.Do not spin the tires in
excess of 56 km/h
(35 mph) on slippery
surfaces such as snow,
mud, ice, etc. Excessive
spinning may cause the
tires to explode.
All-Season Tires
This vehicle may come with
all-season tires. These tires are
designed to provide good overall

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 381
All-Terrain Tires
This vehicle may have all-terrain
tires. These tires provide good
performance on most road surfaces,
weather conditions, and for off-road
driving. SeeOff-Road Driving 0191.
The tread pattern on these tires may
wear more unevenly than other
tires. Consider rotating the tires
more frequently than at 12 000 km
(7,500 mi) intervals if irregular wear
is noted when the tires are
inspected. See Tire Inspection
0 396.
Tire Sidewall Labeling
Useful information about a tire is
molded into the sidewall. The
examples show a typical
passenger and light truck tire
sidewall.
Passenger (P-Metric)/Spare Tire
(1) Tire Size:The tire size code
is a combination of letters and
numbers used to define a
particular tire's width, height,
aspect ratio, construction type,
and service description. See the
“Tire Size” illustration later in this
section.
(2) TPC Spec (Tire
Performance Criteria
Specification)
:Original
equipment tires designed to
GM's specific tire performance
criteria have a TPC specification code molded onto the sidewall.
GM's TPC specifications meet or
exceed all federal safety
guidelines.
(3) DOT (Department of
Transportation)
:The
Department of Transportation
(DOT) code indicates that the
tire is in compliance with the
U.S. Department of
Transportation Motor Vehicle
Safety Standards.
DOT Tire Date of
Manufacture
:The last four
digits of the TIN indicate the tire
manufactured date. The first two
digits represent the week
(01-52) and the last two digits,
the year. For example, the third
week of the year 2010 would
have a four-digit DOT date
of 0310.
(4) Tire Identification Number
(TIN)
:The letters and numbers
following the DOT code are the
Tire Identification Number (TIN).