2020 GMC SIERRA Owner's Manual

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
288 Driving and Operating
.Vehicles can tow in D (Drive).
Tow/Haul Mode is recommended
for heavier trailers. See Tow/
Haul Mode 0226. If the
transmission downshifts too
often, a lower gear may be
selected using Manual Mode.
See Manual Mode 0224.
If equipped, the following driver
assistance features should be
turned off when towing a trailer:
. Adaptive Cruise Control (ACC)
. Super Cruise Control
. Lane Keep Assist (LKA)
. Park Assist
. Automatic Parking Assist (APA)
. Reverse Automatic
Braking (RAB)
If equipped, the following driver
assistance features should be
turned to alert or off when towing a
trailer:
. Automatic Emergency
Braking (AEB)
. Intelligent Brake Assist (IBA) .
Front Pedestrian Braking (FPB)
If equipped with Lane Change Alert
(LCA), the LCA detection zones that
extend back from the side of the
vehicle do not move further back
when a trailer is towed. Use caution
while changing lanes when towing a
trailer.
If equipped with Rear Cross Traffic
Alert (RCTA), use caution while
backing up when towing a trailer, as
the RCTA detection zones that
extend out from the back of the
vehicle do not move further back
when a trailer is towed.
{Warning
To prevent serious injury or death
from carbon monoxide (CO),
when towing a trailer: . Do not drive with the
liftgate, trunk/hatch,
or rear-most window open.
(Continued)
Warning (Continued)
.Fully open the air outlets on
or under the instrument
panel.
. Adjust the climate control
system to a setting that
brings in only outside air.
See “Climate Control
Systems” in the Index.
For more information about
carbon monoxide, see Engine
Exhaust 0220.
Towing a trailer requires experience.
The combination of the vehicle and
trailer is longer and not as
responsive as the vehicle itself. Get
used to the handling and braking of
the combination by driving on a
level road surface before driving on
public roads.
The trailer structure, the tires, and
the brakes must all be rated to carry
the intended cargo. Inadequate
trailer equipment can cause the
combination to operate in an

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 289
unexpected or unsafe manner.
Before driving, inspect all trailer
hitch parts and attachments, safety
chains, electrical connectors, lamps,
tires, and mirrors. SeeTowing
Equipment 0296. If the trailer has
electric brakes, start the
combination moving and then
manually apply the trailer brake
controller to check that the trailer
brakes work. During the trip,
occasionally check that the cargo
and trailer are secure and that the
lamps and any trailer brakes are
working.
Towing with a Stability Control
System
When towing, the stability control
system might be heard. The system
reacts to vehicle movement caused
by the trailer, which mainly occurs
during cornering. This is normal
when towing heavier trailers.
Following Distance
Stay at least twice as far behind the
vehicle ahead as you would when
driving without a trailer. This can
help to avoid heavy braking and
sudden turns.
Passing
More passing distance is needed
when towing a trailer. The
combination of the vehicle and
trailer will not accelerate as quickly
and is much longer than the vehicle
alone. It is necessary to go much
farther beyond the passed vehicle
before returning to the lane. Pass
on level roadways. Avoid passing
on hills if possible.
Backing Up
Hold the bottom of the steering
wheel with one hand. To move the
trailer to the left, move that hand to
the left. To move the trailer to the
right, move that hand to the right.
Always back up slowly and,
if possible, have someone
guide you.
Making Turns
Caution
Turn more slowly and make wider
arcs when towing a trailer to
prevent damage to your vehicle.
Making very sharp turns could
cause the trailer to contact the
vehicle.
Make wider turns than normal when
towing, so the trailer will not go over
soft shoulders, over curbs, or strike
road signs, trees, or other objects.
Always signal turns well in advance.
Do not steer or brake suddenly.
Driving on Grades
Reduce speed and shift to a lower
gear before starting down a long or
steep downhill grade. If the
transmission is not shifted down, the
brakes may overheat and result in
reduced braking efficiency.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
290 Driving and Operating
The vehicle can tow in D (Drive).
Shift the transmission to a lower
gear if the transmission shifts too
often under heavy loads and/or hilly
conditions.
When towing at higher altitudes,
engine coolant will boil at a lower
temperature than at lower altitudes.
If the engine is turned off
immediately after towing at high
altitude on steep uphill grades, the
vehicle could show signs similar to
engine overheating. To avoid this,
let the engine run, preferably on
level ground, with the transmission
in P (Park) for a few minutes before
turning the engine off. If the
overheat warning comes on, see
Engine Overheating0351.
Viewing Systems
If equipped, the viewing systems on
the vehicle can improve visibility
while hitching, backing, and driving
with a trailer. See Driver Assistance
Systems 0256.
Parking on Hills
{Warning
To prevent serious injury or death,
always park your vehicle and
trailer on a level surface when
possible.
When parking your vehicle and your
trailer on a hill: 1. Press the brake pedal, but do not shift into P (Park) yet. Turn
the wheels into the curb if
facing downhill or into traffic if
facing uphill.
2. Have someone place chocks under the trailer wheels.
3. Gradually release the brake pedal to allow the chocks to
absorb the load of the trailer.
4. Reapply the brake pedal. Then apply the parking brake and
shift into P (Park).
5. Release the brake pedal.
Leaving After Parking on a Hill
1. Apply and hold the brake pedal.
.Start the engine.
. Shift into a gear.
. Release the parking brake.
2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick up and store the chocks.
Launching and Retrieving
a Boat
Backing the Trailer into the Water
{Warning
.Have all passengers get out
of the vehicle before
backing onto the sloped part
of the ramp. Lower the
driver and passenger side
windows before backing
onto the ramp. This will
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 291
Warning (Continued)
provide a means of escape
in the unlikely event the
vehicle slides into the water.
. If the boat launch surface is
slippery, have the driver
remain in the vehicle with
the brake pedal applied
while the boat is being
launched. The boat launch
can be especially slippery at
low tide when part of the
ramp was previously
submerged at high tide. Do
not back onto the ramp to
launch the boat if you are
not sure the vehicle can
maintain traction.
. Do not move the vehicle if
someone is in the path of
the trailer. Some parts of the
trailer might be underwater
and not visible to people
who are assisting in
launching the boat. Disconnect the wiring to the trailer
before backing the trailer into the
water to prevent damage to the
electrical circuits on the trailer.
Reconnect the wiring to the trailer
after removing the trailer from the
water. If the trailer has electric
brakes that can function when the
trailer is submerged, it might help to
leave the electrical trailer connector
attached to maintain trailer brake
functionality while on the boat ramp.
To back the trailer into the water:
1. If equipped, place the vehicle in four-wheel-drive high.
2. Slowly back down the boat ramp until the boat is floating,
but no further than necessary.
3. Press and hold the brake pedal, but do not shift into
P (Park) yet.
4. Have someone place chocks under the front wheels of the
vehicle.
5. Gradually release the brake pedal to allow the chocks to
absorb the load of the trailer. 6. Reapply the brake pedal. Then
apply the parking brake and
shift into P (Park).
7. Release the brake pedal.
Pulling the Trailer from the Water
To pull the trailer out of the water: 1. Press and hold the brake pedal.
2. Start the engine and shift into gear.
3. Release the parking brake.
4. Let up on the brake pedal.
5. Drive slowly until the tires are clear of the chocks.
6. Stop and have someone pick up and store the chocks.
7. Slowly pull the trailer from the water.
8. Once the vehicle and trailer have been driven from the
sloped part of the boat ramp,
the vehicle can be shifted from
four-wheel-drive high. Shift into

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
292 Driving and Operating
the drive mode that is
appropriate for the road
conditions.
Caution
If the vehicle tires begin to spin
and the vehicle begins to slide
toward the water, remove your
foot from the accelerator pedal
and apply the brake pedal. Seek
help to have the vehicle towed up
the ramp.
Maintenance when Trailer
Towing
The vehicle needs service more
often when used to tow trailers. See
Maintenance Schedule0442. It is
especially important to check the
engine oil, axle lubricant, belts,
cooling system, and brake system
before and during each trip.
Check periodically to see that all
nuts and bolts on the trailer hitch
are tight.
Engine Cooling When Trailer
Towing
The cooling system may temporarily
overheat during severe operating
conditions. See Engine Overheating
0 351.
Trailer Towing
If equipped with a diesel engine,
see the Duramax diesel
supplement.
Caution
Towing a trailer improperly can
damage the vehicle and result in
costly repairs not covered by the
vehicle warranty. To tow a trailer
correctly, follow the directions in
this section and see your dealer
for important information about
towing a trailer with the vehicle.
Trailering is different than just
driving the vehicle by itself.
Trailering means changes in
handling, acceleration, braking,
durability, and fuel economy. Successful, safe trailering takes
correct equipment, and it has to be
used properly.
The following information has many
time-tested, important trailering tips
and safety rules. Many of these are
important for your safety and that of
your passengers. Read this section
carefully before pulling a trailer.
Trailer Weight
{Warning
Never exceed the towing capacity
for your vehicle.
Safe trailering requires monitoring
the weight, speed, altitude, road
grades, outside temperature, and
how frequently the vehicle is used to
tow a trailer.
Trailer Weight Ratings
When towing a trailer, the combined
weight of the vehicle, vehicle
contents, trailer, and trailer contents

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 293
must be below all of the maximum
weight ratings for the vehicle,
including:
.GCWR: Gross Combined Weight
Rating
. GVWR: Gross Vehicle Weight
Rating
. Maximum Trailer Weight Rating
. GAWR-RR: Gross Axle Weight
Rating-Rear
. Maximum Trailer Tongue Weight
Rating
See “Weight-Distributing Hitch and
Adjustment” underTowing
Equipment 0296 to determine if
equalizer bars are required to obtain
the maximum trailer weight rating.
See “Trailer Brakes” underTowing
Equipment 0296 to determine if
brakes are required based on your
trailer's weight.
The only way to be sure the weight
is not exceeding any of these
ratings is to weigh the tow vehicle
and trailer combination, fully loaded
for the trip, getting individual
weights for each of these items. A trailering information label on the
B-pillar shows tow rating information
for the vehicle.
{Warning
You and others could be seriously
injured or killed if the trailer is too
heavy or the trailer brakes are
inadequate for the load. The
vehicle may be damaged, and the
repairs would not be covered by
the vehicle warranty.
Only tow a trailer if all the steps in
this section have been followed.
Ask your dealer for advice and
information about towing a trailer.
Gross Combined Weight
Rating (GCWR)
GCWR is the total allowable weight
of the completely loaded vehicle
and trailer including any fuel,
passengers, cargo, equipment, and
accessories. Do not exceed the
GCWR for your vehicle. The GCWR
for the vehicle is on the Trailering
Information Label.
To check that the weight of the
vehicle and trailer are within the
GCWR for the vehicle, follow these
steps:
1. Start with the "curb weight" from the Trailering Information
Label.
2. Add the weight of the trailer loaded with cargo and ready
for the trip.
3. Add the weight of all passengers.
4. Add the weight of all cargo in the vehicle.
5. Add the weight of hitch hardware such as a draw bar,
ball, load equalizer bars,
or sway bars.
6. Add the weight of any accessories or aftermarket
equipment added to the
vehicle.
The resulting weight cannot exceed
the GCWR value on the Trailering
Information Label.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
294 Driving and Operating
The gross combined weight can
also be confirmed by weighing the
truck and trailer on a public scale.
The truck and trailer should be
loaded for the trip with passengers
and cargo.
Gross Vehicle Weight
Rating (GVWR)
For information about the vehicle's
maximum load capacity, seeVehicle
Load Limits 0200. When calculating
the GVWR with a trailer attached,
the trailer tongue weight must be
included as part of the weight the
vehicle is carrying.
Maximum Trailer Weight
The maximum trailer weight rating is
calculated assuming the tow vehicle
has a driver, a front seat passenger,
and all required trailering
equipment. This value represents
the heaviest trailer the vehicle can
tow, but it may be necessary to
reduce the trailer weight to stay
within the GCWR, GVWR, maximum
trailer tongue load, or GAWR-RR for
the vehicle.
Use the Tow Rating Guide
(my.gmc.com/learn) to determine
how much the trailer can weigh,
based on the vehicle model and
options.
Weights listed apply for
conventional trailers and
gooseneck/fifth-wheel trailers unless
otherwise noted.
A step bumper trailer hitch can only
support a total trailer weight up to
2 271 kg (5,000 lb). If a trailer hitch
ball is added to the step bumper,
check the hitch ball rating to be sure
it is higher than the total trailer
weight.
Maximum Trailer Tongue
Weight Rating
The Maximum Trailer Tongue
Weight Rating is the allowable
trailer tongue weight that the vehicle
can support using a conventional
trailer hitch. It may be necessary to
reduce the overall trailer weight to
stay within the maximum trailer
tongue weight rating while still
maintaining the correct trailer load
balance. A fifth-wheel or gooseneck
hitch may support a higher tongue
weight.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 295
The Maximum Trailer Tongue
Weight Rating for a conventional
trailer hitch or a fifth wheel/
gooseneck hitch is shown on the
Trailering Information Label.
Do not exceed a maximum trailer
tongue weight of 567 kg (1,250 lb)
for a conventional trailer hitch.
The trailer tongue weight contributes
to the Gross Vehicle Weight (GVW).
GVW includes the curb weight of
your vehicle, any passengers,
cargo, equipment and the trailer
tongue weight. Vehicle options,
passengers, cargo, and equipment
reduce the maximum allowable
tongue weight the vehicle can carry,
which also reduces the maximum
allowable trailer weight.
Trailer Load Balance
The correct trailer load balance
must be maintained to ensure trailer
stability. Incorrect load balance is a
leading cause of trailer sway.
The trailer tongue weight (1) should
be 10–15% and fifth-wheel or
gooseneck tongue weight should be
15–25% of the total loaded trailer
weight (2). Some specific trailer
types, such as boat trailers, fall
outside of this range. Always refer
to the trailer owner’s manual for the
recommended trailer tongue weight
for each trailer. Never exceed the
maximum loads for the vehicle,
hitch, and trailer.
The trailer load balance percentage
is calculated as: weight (1) divided
by weight (2) times 100. After loading the trailer, separately
weigh the trailer and then the trailer
tongue and calculate the trailer load
balance percentage to see if the
weights and distribution are
appropriate for your vehicle. If the
trailer weight is too high, it may be
possible to transfer some of the
cargo into your vehicle. If the trailer
tongue weight is too high or too low,
it may be possible to rearrange
some of the cargo inside of the
trailer.
Do not exceed the maximum
allowable tongue weight for your
vehicle. Use the shortest hitch
extension available to position the
hitch ball closer to your vehicle. This
will help reduce the effect of the
trailer tongue weight on the trailer
hitch and the rear axle.
If a cargo carrier is used in the
trailer hitch receiver, choose a
carrier that positions the load as
close to the vehicle as possible.
Make sure the total weight,
including the carrier, is no more than