towing GMC SIERRA 2020 Service Manual

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
308 Driving and Operating
To determine whether the electrical
fault is on the vehicle side or trailer
side of the trailer wiring harness
connection:1. Disconnect the trailer wiring harness from the vehicle.
2. Turn the ignition off.
3. Wait 10 seconds, then turn the ignition back to RUN.
4. If the CHECK TRAILER WIRING message reappears,
the electrical fault is on the
vehicle side.
If the CHECK TRAILER WIRING
message only reappears when
connecting the trailer wiring harness
to the vehicle, the electrical fault is
on the trailer side.
SERVICE TRAILER BRAKE
SYSTEM: This message will display
when there is a problem with the
ITBC system. If this message
continues over multiple ignition
cycles, have the vehicle serviced.
If either the CHECK TRAILER
WIRING or SERVICE TRAILER
BRAKE SYSTEM message displays while driving, the ITBC system may
not be fully functional or may not
function at all. When traffic
conditions allow, carefully pull the
vehicle over to the side of the road
and turn the ignition off. Check the
wiring connection to the trailer and
turn the ignition back on. If either of
these messages continues, either
the vehicle or trailer needs service.
A GM dealer may be able to
diagnose and repair problems with
the trailer. However, any diagnosis
and repair of the trailer is not
covered under the vehicle warranty.
Contact your trailer dealer for
assistance with trailer repairs and
trailer warranty information.
Trailer Sway
Control (TSC)
Vehicles with StabiliTrak/Electronic
Stability Control (ESC) have a
Trailer Sway Control (TSC) feature.
Trailer sway is unintended
side-to-side motion of a trailer while
towing. If the vehicle is towing a
trailer and the TSC detects that
sway is increasing, the vehiclebrakes are selectively applied at
each wheel, to help reduce
excessive trailer sway. If equipped
with the Integrated Trailer Brake
Control (ITBC) system, and the
trailer has an electric brake system,
StabiliTrak/ESC may also apply the
trailer brakes.If TSC is enabled, the Traction
Control System (TCS)/StabiliTrak/
ESC warning light will flash on the
instrument cluster. Reduce vehicle
speed by gradually removing your
foot from the accelerator. If trailer
sway continues, StabiliTrak/ESC
can reduce engine torque to help

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
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Driving and Operating 309
slow the vehicle. TSC will not
function if StabiliTrak/ESC is turned
off. SeeTraction Control/Electronic
Stability Control 0235.
{Warning
Trailer sway can result in a crash
and in serious injury or death,
even if the vehicle is equipped
with TSC.
If the trailer begins to sway,
reduce vehicle speed by
gradually removing your foot from
the accelerator. Then pull over to
check the trailer and vehicle to
help correct possible causes,
including an improperly or
overloaded trailer, unrestrained
cargo, improper trailer hitch
configuration, or improperly
inflated or incorrect vehicle or
trailer tires. See Towing
Equipment 0296 for trailer ratings
and hitch setup
recommendations.
Aftermarket Electronic Trailer
Sway Control Devices
Some trailers may come equipped
with an electronic device designed
to reduce or control trailer sway.
Aftermarket equipment
manufacturers also offer similar
devices that connect to the wiring
between the trailer and the vehicle.
These devices may interfere with
the vehicle’ s trailer brake or other
systems, including integrated
anti-sway systems, if equipped.
Messages related to trailer
connections or trailer brakes could
appear on the DIC. The effects of
these aftermarket devices may have
on vehicle handling or trailer brake
performance is not known.
{Warning
Use of aftermarket electronic
trailer sway control devices could
result in reduced trailer brake
performance, loss of trailer
brakes, or other malfunctions, and
(Continued)
Warning (Continued)
result in a crash. You or others
could be seriously injured or
killed. Before using one of these
devices:
. Ask the device or trailer
manufacturer if the device
has been thoroughly tested
for compatibility with the
make, model, and year of
your vehicle and any
optional equipment installed
on your vehicle.
. Before driving, check the
trailer brakes are working
properly, if equipped. Drive
the vehicle with the trailer
attached on a level road
surface that is free of traffic
at about 32-40 km/h
(20-25 mph) and fully apply
the manual trailer brake
apply lever. Also, check the
trailer brake lamps and
other lamps are functioning
correctly.
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 311
Touch Stop to stop the test. The test
will automatically end after
one minute and 45 seconds.
The sequence also deactivates
when any of the following occur:
.The ignition is turned off.
. The transmission is shifted out
of P (Park).
. The brake pedal is pressed.
. The turn signal is activated.
. The hazard warning lights are
activated.
Trailering App
If equipped, the Trailering App is on
the Home Page of the infotainment
display.
If equipped this feature allows
profiles for connected trailers to be
created to view status, to store and
track trailer usage information, and
to set up towing assistance
features.
The Trailering App Preview will
appear when the Trailering App is
opened for the first time from the Home Page. Touch GET STARTED
in the Trailering App to go into
the app.
When a trailer is electrically
connected, there will be an option to
create a profile, use a guest profile,
or cancel. After Cancel is selected a
third time, Don’t Remind Me will
display and touching that will turn off
the trailer detection pop-up. To turn
the Trailer Detection Alert on, select
ON in the Settings tab.
When a trailer is electrically
connected and after a Trailer Profile
has been created, the trailer
detection pop-up will appear with a
list of all of the custom Trailer
Profiles made on the vehicle. To
load an existing Trailer Profile,
select one of the Trailer Profiles
listed, or load the Guest Trailer
Profile by selecting GUEST
TRAILER. Touching Cancel,
Accessory/No trailer, or shifting the
vehicle from P (Park), will select
Accessory/No trailer as the active
Trailer Profile and will dismiss the
pop- up.
Create a Trailer Profile
1. Touch Create Profile on the pop-up or touch + Add Trailer
in the Trailering App.
2. Create a name for the trailer.
3. Select the hitch type. A checklist profile will be
created based on the type
selected.
4. Select the trailer type.
A pop-up will indicate the setup is
complete. Touch DONE to complete
the process or touch TRAILER
FEATURE SETUP to set up the
Tow/Haul Mode reminder, Trailer
Tire Pressure Monitoring System,
if equipped, maintenance reminders,
or towing assistance, if equipped.
Import a Trailer Profile
A trailer profile saved to an OnStar
account can be imported to the
vehicle. 1. Touch Import Profile on the pop-up.
2. Select a trailer profile from the list.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
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Driving and Operating 313
3. Activate the tool near the valvestem or adjust the air pressure
of this tire until the horn chirps
and all working vehicle and
trailer lights flash.
The process stops without
saving the sensor locations if
this step takes more than
two minutes.
4. Move to the next tire and repeat Step 3 for each sensor.
The horn chirps twice when all
sensors are completed.
5. Return to the vehicle to complete the setup.
Maintenance Reminders
To set up maintenance reminders,
touch the Trailer Maintenance icon.
Select Yes to set up the
maintenance reminders for the
Trailer Profile. Follow the on-screen
prompts. The maximum number of
reminders is 50. Select No to return
to the previous screen.
Towing Assistance
If the Transparent Trailer feature is
available, touch the Towing
Assistance icon to set up
transparent trailer.
Touch Yes to begin set up or touch
No to return to the previous screen.
Follow the on-screen instructions.
A rear trailer camera must be
mounted on the trailer and
electrically connected to the vehicle
before transparent trailer feature
can be used. See Assistance
Systems for Parking or Backing
0 257.
Trailer dimensions must be in range
and transparent trailer must be
calibrated prior to use.
Transparent Trailer Setup
To complete setup for transparent
trailer: 1. Select the number of axles on the trailer. 2. Enter trailer dimensions
.Trailer Length: 300 cm
(118.1 in) 970 cm (381.8
in). Measure from center of
coupler to furthest rear
point on the trailer.
. Trailer Width: 120 cm (47.2
in) 260 cm (102.3 in).
Measure from left edge to
right edge.
. Trailer Height: 1 cm
(.39 in) –450 cm (177.1 in).
Measure from ground to
tallest point.
. Hitching Point Length: 180
cm (70.8 in) –970
cm (381.8 in). Measure from
center of coupler to middle
of tires.
. Trailer Tongue Length: 50
cm (119.6 in) –220
cm (86.6 in). Measure from
center of coupler to trailer
front wall.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
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Driving and Operating 317
Cameras
1. Rear Trailer Not Connected/Preview, if equipped
2. Interior Trailer Not Connected/Preview,
if equipped
3. Transparent Trailer Not Set Up/Preview, if equipped
The Cameras Status view displays
status of trailer cameras.
Touch a connected camera to
preview the camera image.
Touch the Transparent Trailer option
to enter Transparent Trailer Setup if
setup is not complete.
Guest Trailer Status View
Touch the Guest Trailer Profile for
the status views.
The Guest Trailer Profile Status
view shows:
.Truck
. Trailer
. Connections
. Cameras, if equipped
The Trailer Status view displays
mileage information. Touch to edit,
and follow the on-screen prompts.
Mileage and fuel economy will reset
after the trailer disconnects. The
Cameras Status view displays
status of trailer cameras. Touch a
connected camera to preview the
camera image.
Checklist View
This view shows the recommended
steps to take before towing a trailer.
Touch the box next to each item if
that step has been completed. Touch
pto access a detailed
view of each step. Within each
detailed view, touch Next and
Previous to navigate between steps.
Touch Clear All to clear the
completed statuses from all items in
the current checklist.
The checklist is unique to the Trailer
Profile based on hitch type; for
example, the steps involve different
details between conventional,
gooseneck, and fifth-wheel hitch
types.
Custom Checklist Items
For each of the Trailer Profile
checklists, there is an option to
create custom items to view in the
checklist. The custom item will
appear at the bottom of the
checklist.
Guest Trailer and No Trailer
Connected
If Guest Trailer Profile is active or if
no trailer is connected, the checklist
will show all of the checklists

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
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318 Driving and Operating
associated with Custom Trailer
Profiles in addition to default
checklists.
Trailers View
Touch the Trailers tab to view,
activate, create, edit, or delete
Trailer Profiles.
If a trailer is connected, touch the
Trailer Profile name to activate a
Trailer Profile.
There can be up to five Custom
Trailer Profiles on the vehicle.
The Custom Trailer Profiles and
Guest Trailer are in order of the
most frequently used.
All personalization features are
based on the settings for each
driver in vehicle personalization.
The list of Trailer Profiles is based
on vehicle personalization settings.
Guest Trailer
If the Guest Trailer Profile is the
active Trailer Profile, trailer
detection, connections status, theft,
and the Tow/Haul reminder alerts
can be sent. The system will nottrack total mileage or fuel economy,
but the system will track trip mileage
and fuel economy if the Guest
Trailer Profile is active. The Trailer
Tire Pressure Monitoring System or
maintenance reminders cannot be
set up for a Guest Trailer Profile.
The Guest Trailer Profile cannot be
edited.
Touch
pto learn more about the
Guest Trailer option.
No Trailer Connected
When there is no trailer connected,
Trailer Profiles cannot be activated
but most options can be edited.
Trailer Brake Gain Memory
The system can memorize the brake
gain setting of a Trailer Profile or a
Guest Trailer Profile. When a Trailer
Profile or Guest Trailer Profile is
selected, and a brake gain setting is
set for that Trailer Profile, a quick
notice will appear to indicate that
the system has recalled that
profile’s brake gain setting. If a Trailer Profile is already active
and the brake gain setting had been
set for that Trailer Profile, the quick
notice will trigger whenever the
ignition is turned on.
If there was an error in setting the
brake gain for a Trailer Profile, there
will be a notification. This pop-up
will not appear if the Guest Trailer
Profile is active or if there is no
trailer connected.
Trailer brake gain should be set for
a specific trailering condition and
must be adjusted anytime vehicle
loading, trailer loading, or road
surface conditions change.
Editing a Trailer Profile
Trailer Profile View
Touch to edit any of the following
options in the Trailer Profile view:
.
Trailer Name
. Towing Assistance Setup
. Tire Pressure Setup
. Trailer Maintenance
. Mileage

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Driving and Operating 319
.Average Fuel Economy
. Reverse Lights Alert
. Electric Brakes Alert
Touch Save to save the new value
to the Trailer Profile. Touching Back
will still save the previously entered
information.
Trailer Name
Touch to edit the Trailer Profile’s
name. Use at least one character
and no spaces. Touch Save.
Towing Assistance Setup
A trailer should be connected to
complete this portion of profile
setup.
Touch to set up the Transparent
Trailer feature for the Trailer Profile.
See "Transparent Trailer Setup"
under "Towing Assistance" for
details on the setup.
Tire Pressure Setup
Touch to set up the Trailer Tire
Pressure Monitoring System
(TTPMS) for the Trailer Profile. See
“Trailer Tire Pressure Setup” previously in this section for details
on the setup. Also, touch Tire
Pressure Setup if the trailer tires
were rotated or if the tire pressure
sensors in the tires were replaced
for this Trailer Profile. The vehicle
will need to relearn the tire sensors
and their locations.
If TTPMS had been set up
previously, the Select Number of
Sensors screen will appear after
touching Tire Pressure Setup. If the
number of sensors has changed,
select the number and touch Next.
If a new number of sensors is
selected, the Relearn Sensors
pop-up will appear. Touch Cancel to
go back or touch Relearn to
overwrite the current sensors and
begin the relearning process. See
“Trailer Tire Pressure Setup”
previously in this section.
If number of sensors has not
changed, touch Next and the Learn
sensors screen will appear.
On the Learn Sensors screen.
Touch Relearn to overwrite the
current sensors and begin therelearning process. See
“Trailer Tire
Pressure Setup” previously in this
section.
On the Learn Sensors screen, touch
Next to go to the Edit
Recommended Tire Pressure
screen.
On the Edit Recommended Tire
Pressure screen, touch a number on
the keypad to change the
Recommended Tire Pressure for the
trailer ’s tires. This will change the
number at which the vehicle
displays alerts related to trailer tire
pressure. Touch Done to return to
the Trailer Profile view.
Trailer Maintenance
Touch to view a list of maintenance
reminders for the Trailer Profile.
Touch a reminder to view, reset,
delete, or edit it.
Reset Reminder
Touch Maintenance Complete in the
reminder view to reset the reminder.
On the pop-up, touch Reset to reset
the time and mileage values for the

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Driving and Operating 321
Trailer Detection Alert
The Trailer Detection Alert setting
will be on by default. Turn it off to
disable the Trailer Detection pop-up
from displaying when a trailer is
connected. The Guest Trailer Profile
will become the active Trailer
Profile, unless another Trailer Profile
is selected manually through the
Trailering App. If this setting is
disabled while a Custom Trailer
Profile is active, that Trailer Profile
will remain the active profile until the
trailer is disconnected.
Maintenance Alerts
Touch Maintenance Alerts to view
the Maintenance Alerts settings
page. These alerts are based on the
Trailer Profile, so the settings for
each Trailer Profile must be turned
on or off. Touch a profile to view
more information or adjust the
setting for that profile.
The setting will be on by default for
each profile. All Maintenance Alerts
for that active Trailer Profile will be
received.Turn a setting off to not receive any
of the Maintenance Alerts when that
Trailer Profile is active.
Theft Alert
A theft alert can be set if a trailer is
connected and the alert is enabled.
When the trailer is disconnected
and the vehicle is off, an alarm will
sound.
Touch Theft Alert in Settings to view
the Theft Alert settings page. These
alerts are based on the Trailer
Profile, so the settings for each
Trailer Profile must be turned on or
off. Touch a profile to view more
information or adjust the setting for
that profile.
This setting will be off by default for
each Trailer Profile, including the
Guest Trailer Profile.
A smartphone will receive a
notification that the trailer related to
the selected Trailer Profile is
disconnected from the vehicle, if the
setting is on for the active Trailer
Profile, the vehicle has an OnStar or
connected service plan and thesmartphone number has been
added to the account for this
notification.
If the setting is turned off for a given
Trailer Profile, the smartphone will
not receive this security notification
even if the Trailer Profile is active.
Tow/Haul Mode Reminder
This is a reminder to turn on the
Tow/Haul Mode when towing a
trailer. See
Tow/Haul Mode 0226.
Touch Tow/Haul Mode Reminder in
Settings to view the Tow/Haul Mode
Reminder settings page. These
alerts are based on the Trailer
Profile, so the settings for each
Trailer Profile must be turned on or
off. Touch a profile to view more
information or to adjust the setting
for that profile.
This setting will default to OFF for
each Trailer Profile, including the
Guest Trailer Profile.
If Tow/Haul Mode is off and this
setting is on for a Trailer Profile,
each time the ignition is turned on a

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
328 Vehicle Care
Tire Pressure . . . . . . . . . . . . . . . . . 387
Tire Pressure for High-SpeedOperation . . . . . . . . . . . . . . . . . . . 389
Tire Pressure Monitor System . . . . . . . . . . . . . . . . . . . . . . 389
Tire Pressure Monitor Operation . . . . . . . . . . . . . . . . . . . 390
Tire Inspection . . . . . . . . . . . . . . . . 396
Tire Rotation . . . . . . . . . . . . . . . . . 396
When It Is Time for New Tires . . . . . . . . . . . . . . . . . . . . . . . . 398
Buying New Tires . . . . . . . . . . . . . 399
Different Size Tires and Wheels . . . . . . . . . . . . . . . . . . . . . . 401
Uniform Tire Quality Grading . . . . . . . . . . . . . . . . . . . . . 401
Wheel Alignment and Tire Balance . . . . . . . . . . . . . . . . . . . . . 403
Wheel Replacement . . . . . . . . . . 403
Tire Chains . . . . . . . . . . . . . . . . . . . 404
If a Tire Goes Flat . . . . . . . . . . . . 405
Tire Changing . . . . . . . . . . . . . . . . 407
Full-Size Spare Tire . . . . . . . . . . 418
Jump Starting
Jump Starting - North America . . . . . . . . . . . . . . . . . . . . . 419
Towing the Vehicle
Towing the Vehicle . . . . . . . . . . . 424 Recreational Vehicle
Towing . . . . . . . . . . . . . . . . . . . . . . 424
Appearance Care
Exterior Care . . . . . . . . . . . . . . . . . 429
Interior Care . . . . . . . . . . . . . . . . . . 435
Floor Mats . . . . . . . . . . . . . . . . . . . . 438
General Information
For service and parts needs, visit
your dealer. You will receive
genuine GM parts and GM-trained
and supported service people.
Genuine GM parts have one of
these marks:

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
352 Vehicle Care
If No Steam is Coming from
the Engine Compartment
The ENGINE OVERHEATED STOP
ENGINE or the ENGINE
OVERHEATED IDLE ENGINE
message, along with a low coolant
condition, can indicate a serious
problem.
The 2.7L L4 engine will shut down
automatically if the ENGINE
OVERHEATED STOP ENGINE
message displays.
If there is an engine overheat
warning, but no steam is seen or
heard, the problem may not be too
serious. Sometimes the engine can
get a little too hot when the vehicle:
.Climbs a long hill on a hot day.
. Stops after high-speed driving.
. Idles for long periods in traffic.
. Tows a trailer; see Trailer Towing
0 292. If the ENGINE OVERHEATED
STOP ENGINE or the ENGINE
OVERHEATED IDLE ENGINE
message appears with no sign of
steam, try this for a minute or so:
1. Turn the air conditioning off.
2. Turn the heater on to the highest temperature and to the
highest fan speed. Open the
windows as necessary.
3. When it is safe to do so, pull off the road, shift to P (Park) or
N (Neutral) and let the
engine idle.
If the temperature overheat gauge is
no longer in the overheat zone or an
overheat warning no longer
displays, the vehicle can be driven.
Continue to drive the vehicle slowly
for about 10 minutes. Keep a safe
vehicle distance from the vehicle in
front. If the warning does not come
back on, continue to drive normally
and have the cooling system
checked for proper fill and function.
If the warning continues, pull over,
stop, and park the vehicle
right away. If there is still no sign of steam and
the vehicle is equipped with an
engine driven cooling fan, push
down the accelerator until the
engine speed is about twice as fast
as normal idle speed for at least
five minutes while the vehicle is
parked. If the warning is still there,
turn off the engine and get everyone
out of the vehicle until it cools down.
If there is no sign of steam, idle the
engine for five minutes while
parked. If the warning is still
displayed, turn off the engine until it
cools down.
Overheated Engine
Protection
Operating Mode
If an overheated engine condition
exists and the ENGINE POWER IS
REDUCED message displays, an
overheat protection mode which
alternates firing groups of cylinders
helps to prevent engine damage. In
this mode, a loss in power and
engine performance will be noticed.
This operating mode allows the