2020 GMC SIERRA Owner's Manual

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
424 Vehicle Care
Towing the Vehicle
Caution
Incorrectly towing a disabled
vehicle may cause damage. The
damage would not be covered by
the vehicle warranty. Do not lash
or hook to suspension
components. Use the proper
straps around the tires to secure
the vehicle. Do not drag a locked
wheel/tire. Use tire skates or
dollies under any locked wheel/
tire while loading the vehicle. Do
not use a sling type lift to tow the
vehicle. This could damage the
vehicle.
Caution
If the vehicle cannot be shifted
into Neutral (N), do not use the
tow eye to tow the vehicle.
Vehicle damage may occur.GM recommends a flatbed tow truck
to transport a disabled vehicle. Use
ramps to help reduce approach
angles, if necessary. A towed
vehicle should have its drive wheels
off the ground. Contact Roadside
Assistance or a professional towing
service if the disabled vehicle must
be towed.
Front Attachment Points
1500
2500/3500
The vehicle is equipped with
specific attachment points to be
used to pull the vehicle onto a
flatbed car carrier from a flat road
surface. Do not use these
attachment points to pull the vehicle
from snow, mud or sand.
Recreational Vehicle
Towing
Recreational vehicle towing means
towing the vehicle behind another
vehicle, such as a motor home. The
two most common types of
recreational vehicle towing are

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
Vehicle Care 425
dinghy and dolly towing. Dinghy
towing is towing the vehicle with all
four wheels on the ground. Dolly
towing is towing the vehicle with two
wheels on the ground and two
wheels on a dolly.
Here are some important things to
consider before recreational vehicle
towing:
.Before towing the vehicle,
become familiar with the local
laws that apply to recreational
vehicle towing. These laws may
vary by region.
. The towing capacity of the
towing vehicle. Read the tow
vehicle manufacturer's
recommendations.
. How far the vehicle can be
towed. Some vehicles have
restrictions on how far and how
long the vehicle can be towed.
. Whether the vehicle has the
proper towing equipment. See
your dealer or trailering
professional for additional advice
and equipment
recommendations. .
Whether the vehicle is ready to
be towed. Just as preparing the
vehicle for a long trip, make sure
the vehicle is prepared to be
towed.
Follow the tow vehicle
manufacturer ’s instructions.
Caution
Use of a shield mounted in front
of the vehicle grille could restrict
airflow and cause damage to the
transmission. The repairs would
not be covered by the vehicle
warranty. If using a shield, only
use one that attaches to the
towing vehicle.
Dinghy Towing
(Two-Wheel-Drive Vehicles and
Vehicles with a Single-Speed
Transfer Case)
Caution
If a vehicle with two-wheel drive
or a single-speed transfer case is
towed with all four wheels on the
ground, the drivetrain
components could be damaged.
The repairs would not be covered
by the vehicle warranty.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
426 Vehicle Care
Two-wheel-drive vehicles and
vehicles with a single-speed transfer
case should not be towed with all
four wheels on the ground.
Dinghy Towing (Vehicles with a
Two-Speed Transfer Case)
Only dinghy tow four-wheel-drive
vehicles with a two-speed transfer
case that have an N (Neutral) and a
4
n(Four-Wheel Drive Low) setting.
{Warning
Shifting a four-wheel-drive
vehicle's transfer case into
N (Neutral) can allow the vehicle
to move even if the transmission
is in P (Park). You or others could
be injured. Set the parking brake
and use wheel blocks before
shifting the transfer case to
N (Neutral).
To dinghy tow: 1. Position the vehicle being towed behind the tow vehicle,
facing forward and on a level
surface.
2. Securely attach the vehicle being towed to the tow vehicle.
3. Start the engine.
4. Shift the transfer case to N (Neutral). See “Shifting into
N (Neutral)” underFour-Wheel
Drive 0227. 5. With the engine running,
release the parking brake and
verify that the transfer case is
in N (Neutral) by shifting the
transmission to D (Drive) and
then to R (Reverse). There
should be no movement while
shifting the transmission.
6. Shift the transmission to D (Drive).
7. If equipped with an ignition key, turn the ignition to ACC/
ACCESSORY. If equipped with
Keyless Access, turn the
engine off. Disregard the Shift
to P (Park) DIC message. See
Ignition Positions (Keyless
Access) 0208 or
Ignition Positions (Key Access)
0 210.
{Warning
To avoid death, serious injury,
or property damage, before
dinghy towing the vehicle, always
disconnect and secure the
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
Vehicle Care 427
Warning (Continued)
negative battery cable and cover
the negative battery post and
cable with a non-conductive
material. If the battery is left
connected or the battery cable
contacts the post, the Electric
Parking Brake may activate
during towing, which could cause
a crash.
8. Disconnect the negative (–) battery cable. See “Negative
Battery Cable Disconnection”
in Battery - North America
0 358.
9. Shift the transmission to P (Park).
Caution
If the steering column is locked,
vehicle damage may occur.
10. Move the steering wheel to make sure the steering column
is unlocked.
11. If the vehicle has an ignition key, keep it in the towed
vehicle in ACC/ACCESSORY
to prevent the steering column
from locking. If the vehicle is
equipped with Keyless Access,
keep the RKE transmitter
outside of the vehicle and
manually lock the doors.
Access the vehicle by using
the key in the door lock. See
Door Locks 025.
Disconnecting the Towed Vehicle
Before disconnecting from the tow
vehicle: 1. Park on a level surface. Secure the vehicle with wheel blocks. 2. Re-connect the negative (–)
battery. See Battery - North
America 0358.
3. Turn on the ignition with the engine off. For vehicles with a
key, turn the ignition to ON/
RUN with the engine off. If the
vehicle is equipped with
Keyless Access, with your foot
off the brake pedal, press and
hold ENGINE START/STOP for
five seconds until the green
light comes on in the button.
See Ignition Positions (Keyless
Access) 0208 or
Ignition Positions (Key Access)
0 210.
4. Set the parking brake. See Electric Parking Brake 0233.
5. Disconnect from the tow vehicle.
6. Shift the transmission to N (Neutral).
7. Shift the transfer case to 2
m
(Two-Wheel Drive High). When
the shift to 2
m(Two-Wheel
Drive High) is complete, the

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
428 Vehicle Care
light in the instrument cluster
will stop flashing and stay lit.
SeeFour-Wheel-Drive Light
0 142.
8. Start the engine. Check that the vehicle is in 2
m
(Two-Wheel Drive High) by
starting the engine and shifting
the transmission to D (Drive)
and then to R (Reverse). There
should be movement of the
vehicle while shifting.
9. Shift the transmission to P (Park) and turn off the
ignition.
10. Release the parking brake and remove the wheel blocks.
11. Reset any lost presets. The outside temperature
display will default to 0 °C (32 °
F) but will reset with normal
usage.
Dolly TowingCaution
Do not tow this vehicle with two
wheels on the ground, or vehicle
damage could occur. This
damage would not be covered by
the vehicle warranty.
Dolly towing this vehicle is not
allowed with either the front or the
rear tires on the ground for
two-wheel drive or four-wheel drive,
regardless of transfer case.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
Vehicle Care 429
Appearance Care
Exterior Care
Locks
Locks are lubricated at the factory.
Use a de-icing agent only when
absolutely necessary, and have the
locks greased after using. See
Recommended Fluids and
Lubricants0453.
Washing the Vehicle
To preserve the vehicle's finish,
wash it often and out of direct
sunlight.
{Warning
Do not power wash any part of
the vehicle’s interior, including the
vinyl floor covering. This could
damage safety and other systems
in the vehicle, which would not be
covered by the vehicle warranty.
Caution
Do not use petroleum-based,
acidic, or abrasive cleaning
agents as they can damage the
vehicle's paint, metal, or plastic
parts. If damage occurs, it would
not be covered by the vehicle
warranty. Approved cleaning
products can be obtained from
your dealer. Follow all
manufacturer directions regarding
correct product usage, necessary
safety precautions, and
appropriate disposal of any
vehicle care product.
Caution
Avoid using high-pressure
washes closer than 30 cm (12 in)
to the surface of the vehicle. Use
of power washers exceeding
8,274 kPa (1,200 psi) can result
in damage or removal of paint
and decals.
Caution
Do not power wash any
component under the hood that
has this
esymbol.
This could cause damage that
would not be covered by the
vehicle warranty.
Underhood Component Power
Washing
If power washing underhood
components, do not exceed these
limits:
. Fluid pressures of 110 bar
(1600 psi)
. Fluid temperatures of 25°C
(77°F)
. Nozzle must remain 30 cm
(12 in) or farther from
components.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
430 Vehicle Care
Automatic Car Wash
Caution
Some automatic car washes can
cause damage to the vehicle,
wheels and ground effects.
Automatic car washes are not
recommended, due to lack of
clearance for the undercarriage
and/or wide rear tires and wheels.
Caution
Automatic car washes can cause
damage to the vehicle, wheels,
ground effects, and convertible
top (if equipped).
Do not use automatic car washes
due to lack of clearance for the
undercarriage, wide rear tires,
and wheels.
If using an automatic car wash,
follow with the car wash
instructions. The windshield wiper
and rear window wiper, if equipped, must be turned off. Remove any
accessories that may be damaged
or interfere with the car wash
equipment.
See
Power Assist Steps 036 for
cleaning information.
Rinse the vehicle well, before
washing and after, to remove all
cleaning agents completely. If they
are allowed to dry on the surface,
they could stain.
Dry the finish with a soft, clean
chamois or an all-cotton towel to
avoid surface scratches and water
spotting.Finish Care
Application of aftermarket clearcoat
sealant/wax materials is not
recommended. If painted surfaces
are damaged, see your dealer to
have the damage assessed and
repaired. Foreign materials such as
calcium chloride and other salts, ice
melting agents, road oil and tar, tree
sap, bird droppings, chemicals from
industrial chimneys, etc., can
damage the vehicle's finish if they
remain on painted surfaces. Wash the vehicle as soon as possible.
If necessary, use non-abrasive
cleaners that are marked safe for
painted surfaces to remove foreign
matter.
Occasional hand waxing or mild
polishing should be done to remove
residue from the paint finish. See
your dealer for approved cleaning
products.
Do not apply waxes or polishes to
uncoated plastic, vinyl, rubber,
decals, simulated wood, or flat paint
as damage can occur.
Caution
Machine compounding or
aggressive polishing on a
basecoat/clearcoat paint finish
may damage it. Use only
non-abrasive waxes and polishes
that are made for a basecoat/
clearcoat paint finish on the
vehicle.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
Vehicle Care 431
To keep the paint finish looking new,
keep the vehicle garaged or
covered whenever possible.
Protecting Exterior Bright Metal
Moldings
Caution
Failure to clean and protect the
bright metal moldings can result
in a hazy white finish or pitting.
This damage would not be
covered by the vehicle warranty.
The bright metal moldings on the
vehicle are aluminum, chrome or
stainless steel. To prevent damage
always follow these cleaning
instructions:
. Be sure the molding is cool to
the touch before applying any
cleaning solution.
. Use only approved cleaning
solutions for aluminum, chrome
or stainless steel. Some
cleaners are highly acidic or
contain alkaline substances and
can damage the moldings. .
Always dilute a concentrated
cleaner according to the
manufacturer ’s instructions.
. Do not use cleaners that are not
intended for automotive use.
. Use a nonabrasive wax on the
vehicle after washing to protect
and extend the molding finish.
Spray-In Bedliner Care
A spray-in bedliner is a permanent
coating that bonds to the truck bed
and cannot be removed. Promptly
rinse the bedliner surface following
a chemical spill to avoid permanent
damage.
Spray-in bedliners can fade from
oxidation, road dirt, heavy-duty
hauling, and hard water stains.
Clean it periodically by washing off
the loose dirt and using a mild
detergent. To restore the original
appearance, apply the bedliner
conditioner available through your
dealer.
Caution
Using silicone-based products
may damage the bedliner, reduce
the slip-resistant texture, and
attract dirt.
Cleaning Exterior Lamps/
Lenses, Emblems, Decals and
Stripes
Use only lukewarm or cold water, a
soft cloth, and a car washing soap
to clean exterior lamps, lenses,
emblems, decals and stripes. Follow
instructions under "Washing the
Vehicle" previously in this section.
Lamp covers are made of plastic,
and some have a UV protective
coating. Do not clean or wipe them
while they are dry.