2021 GMC SIERRA Owner's Manual

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
304 Driving and Operating
The trailer symbol on the control panel will
light amber when a trailer with electric
brakes is connected.
The ITBC control panel is on the center
stack. SeeInstrument Panel Overview 04.
The control panel allows adjustment to the
amount of output, referred to as Trailer
Gain, available to the trailer brakes and
allows manual application of the trailer
brakes. Use the ITBC control panel and the
DIC trailer brake display page to adjust and
display power output to the trailer brakes.
Trailer Brake DIC Display Page
The ITBC display page indicates:
.Trailer Gain setting
.Output to the trailer brakes
.Trailer connection
.System operational status
To display:
.Scroll through the DIC menu pages
.Press a Trailer Gain (+) or (−) button
.Activate the Manual Trailer Brake Apply
Lever
TRAILER GAIN: Press a Trailer Gain button to
recall the current Trailer Gain setting. Each
press and release of the gain buttons will
then change the Trailer Gain setting. Press the Trailer Gain (+) or (-) to adjust. Press and
hold to continuously adjust the Trailer Gain.
To turn the output to the trailer off, adjust
the Trailer Gain setting to 0.0. This setting
can be adjusted from 0.0 to 10.0 with a
trailer connected or disconnected.
TRAILER OUTPUT: This displays anytime a
trailer with electric brakes is connected.
Output to the trailer brakes is based on the
amount of vehicle braking present and
relative to the Trailer Gain setting. Output is
displayed from 0 to 100% for each gain
setting.
The Trailer Output will indicate
“- - - - - -”on
the Trailer Brake Display Page whenever the
following occur:
.No trailer is connected.
.A trailer without electric brakes is
connected. No DIC message displays.
.A trailer with electric brakes has become
disconnected. A CHECK TRAILER WIRING
message displays on the DIC.
.There is a fault present in the wiring to
the trailer brakes. A CHECK TRAILER
WIRING message displays on the DIC.
.The ITBC system is not working due to a
fault. A SERVICE TRAILER BRAKE SYSTEM
message displays in the DIC.
Manual Trailer Brake Apply Lever
Slide this lever right to apply the trailer’s
electric brakes independent of the vehicle’s
brakes. Use this lever to adjust the Trailer
Gain to achieve proper power output to the
trailer brakes. Under certain circumstances,
this lever can also be used to apply
additional trailer braking. The trailer and
vehicle brake lamps will come on when
either the vehicle brakes or trailer brakes are
applied and properly connected.
Trailer Gain Adjustment Procedure
Trailer Gain should be set for a specific
trailering condition and it must be
readjusted anytime vehicle loading, trailer
loading, or road surface conditions change.
{Warning
Trailer brakes that are over-gained or
under-gained may not stop the vehicle
and the trailer as intended and can result
in a crash. Always follow the instructions
to set the Trailer Gain for the proper
trailer stopping performance.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 305
To adjust Trailer Gain for each towing
condition:1. Drive the vehicle with the trailer attached on a level road surface
representative of the towing condition
and free of traffic at about 32–40 km/h
(20–25 mph) and fully apply the Manual
Trailer Brake Apply Lever.
Adjusting Trailer Gain at speeds lower
than 32–40 km/h (20–25 mph) may
result in an incorrect gain setting.
2. Adjust the Trailer Gain, using the Trailer Gain (+) or (−) adjustment buttons, to
just below the point of trailer wheel
lock-up, indicated by trailer wheel squeal
or tire smoke when a trailer wheel locks.
Trailer wheel lock-up may not occur if
towing a heavily loaded trailer. Adjust
the Trailer Gain to the highest allowable
setting for the towing condition.
3. Readjust Trailer Gain anytime vehicle loading, trailer loading, or road surface
conditions change or if trailer wheel
lock-up is noticed at any time while
towing.Other ITBC-Related DIC Messages
TRAILER CONNECTED: This message will
briefly display when a trailer with electric
brakes is first connected to the vehicle. This
message will automatically turn off in about
10 seconds. This message can be
acknowledged before it automatically
turns off.
CHECK TRAILER WIRING: This message will
display if:
.The ITBC system first determines
connection to a trailer with electric brakes
and then the trailer harness becomes
disconnected from the vehicle.
If the disconnect occurs while the vehicle
is stationary, this message will
automatically turn off in about
30 seconds. This message will also turn
off if it is acknowledged or if the trailer
harness is reconnected.
If the disconnect occurs while the vehicle
is moving, this message will continue
until the ignition is turned off. This
message will also turn off if it is
acknowledged or if the trailer harness is
reconnected.
.There is an electrical fault in the wiring to
the trailer brakes. This message will
continue as long as there is an electrical
fault in the trailer wiring. This message
will also turn off if it is acknowledged.
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.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
306 Driving and Operating
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 vehicle
brakes are selectively applied at each wheel,
to help reduce excessive trailer sway.
If equipped with the Integrated Trailer BrakeControl (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 slow the vehicle. TSC will not
function if StabiliTrak/ESC is turned off. See
Traction Control/Electronic Stability Control
0
248.
{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

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Driving and Operating 307
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 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(Continued)
Warning (Continued)
manual trailer brake apply lever. Also,
check the trailer brake lamps and
other lamps are functioning correctly.
.If the trailer brakes are not operating
properly at any time, or if a DIC
message indicates problems with the
trailer connections or trailer brakes,
carefully pull the vehicle over to the
side of the road when traffic
conditions allow.
Trailer Tires
Special Trailer (ST) tires differ from vehicle
tires. Trailer tires are designed with stiff
sidewalls to help prevent sway and to
support heavy loads. These features can
make it difficult to determine if the trailer
tire pressures are low only based on a visual
inspection.
Always check all trailer tire pressures before
each trip when the tires are cool. Low trailer
tire pressure is a leading cause of trailer tire
blow-outs. If the vehicle is equipped with a trailer tire
pressure monitoring system, see the trailer
tire pressure monitoring system description
and the trailering app.
Trailer tires deteriorate over time. The trailer
tire sidewall will show the week and year
the tire was manufactured. Many trailer tire
manufacturers recommend replacing tires
more than six years old.
Overloading is another leading cause of
trailer tire blow-outs. Never load your trailer
with more weight than the tires are
designed to support. The load rating is
located on the trailer tire sidewall.
Always know the maximum speed rating for
the trailer tires before driving. This may be
significantly lower than the vehicle tire
speed rating. The speed rating may be on
the trailer tire sidewall. If the speed rating is
not shown, the default trailer tire speed
rating is 105 km/h (65 mph).
Trailering App
Trailer Lights App
If equipped, the Trailer Lights App is on the
Home Page of the infotainment display.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
308 Driving and Operating
Touch Start to cycle the trailer lamps on and
off to determine if they are working. The
test follows this sequence:1. The running lights turn on first and remain on throughout the sequence.
2. The brake lights turn on for about two seconds.
3. The left turn signal light flashes three times.
4. The right turn signal light flashes three times.
5. The reverse lights turn on for about two seconds.
6. Steps 2–5 repeat for approximately one minute and 45 seconds, or until the
test deactivates.
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 and
a trailer profile has not been created, there
will be an option to create a profile, use a
guest profile, or select Accessory/No trailer.
After the pop-up is displayed three times,
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
Accessory/No trailer will select Accessory/No
trailer as the active Trailer Profile and will
dismiss the pop- up. Shifting the vehicle
from P (Park) will select Guest Trailer as the
active Trailer Profile and will dismiss the
pop-up.
Create a Trailer Profile
1. Touch Create Profile on the trailer detection pop-up or touch + Add Trailer
Profile in the Trailering App.
2. Create a name for the trailer.
3. Select the trailer type.
4. Select Save Profile.
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 + Add Trailer Profile in the Trailering App

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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Driving and Operating 309
2. Touch Import Profile on the pop-up.
3. Select a trailer profile from the list.
4. Touch IMPORT.
A pop-up will indicate the import was
successful. Touch OK to return to the trailer
list and select the trailer profile. The Tow/
Haul Mode reminder, Brake Gain Setting and
Trailer Tire Pressure sensor learning,
if equipped, do not import.
Trailer Feature Setup
Tow/Haul Mode Reminder
To turn the Tow/Haul Mode Reminder
setting on, touch Yes. To turn it off,
touch No.
Trailer Tire Pressure Setup
If the Trailer Tire Pressure Monitoring
System (TTPMS) is detected, touch the Tire
Pressure Monitoring icon to set up tire
pressure monitoring. Touch Yes to set up
the sensors or touch No to return to the
previous screen.
The trailer tire pressure sensors can transmit
up to 7 m (23 feet) from the hitch receiver of
the vehicle. A trailer must be electrically connected to
the vehicle before starting the
sensor-to-vehicle learn process.
After selecting Start from the Learn Sensors
screen, use the Tool Method or the Manual
Method (described below) to learn each tire
sensor, during which the current tire number
will be highlighted.
Each sensor has a minimum of two minutes
to learn, shown by a timer. After a sensor is
learned, a checkmark appears next to the
tire, the vehicle horn will sound, the
vehicle’s brake lamps will flash, and all
working trailer lamps will flash. It then
moves to the next sensor.
To cancel the process touch Stop.
The recommended tire pressure must be
entered for the trailer tires. This allows the
vehicle to alert when the tire pressure is
high or low.
TTPMS must learn the location of the
installed tire sensors to show correct air
pressure and temperature for each tire. To
set up, use one of the following options or
see a tire or trailer dealer for service. The
learning process must be repeated when thetrailer tires are rotated or replaced. See
“Editing a Trailer Profile”
later in this section
for tire pressure sensor relearn information.
Tool Method: A TTPMS activation tool can
be purchased separately to learn the sensor
locations.
Manual Method: Without the tool, the air
pressure can be increased or decreased in
each tire for 10 seconds. Do not exceed the
maximum inflation pressure found on the
tire sidewalls. Make sure to re-adjust tire
pressure to the recommended level when
the process is complete.
Sensor Learning Steps
To complete the sensor-to-vehicle learn
process:
1. Touch Start on the Learn Sensors screen. The horn chirps twice and the Learning
Active screen appears on the
infotainment display.
2. Start with the driver side front trailer tire.
3. Activate the tool near the valve stem or adjust the air pressure of this tire until
the horn chirps and all working vehicle
and trailer lights flash.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
310 Driving and Operating
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
To set up towing assistance features,
if equipped, touch the Towing
Assistance icon.
Touch Yes to begin set up or touch No to
return to the previous screen.
1. Select the number of axles on the trailer.
2. Enter trailer dimensions as prompted.
3. Follow the on-screen instructions to complete setup for available features.
Transparent Trailer Setup (if equipped)
To complete setup for transparent trailer:
.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 (0.39 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 (19.6 in) –
220 cm (86.6 in). Measure from center of
coupler to trailer front wall.
.Vehicle Hitch Height: 10 cm (3.9 in) –
100 cm (39.3 in). Measure from ground to
top of coupler.
.Vehicle Hitch Length: 10 cm (3.9 in) –
100 cm (39.3 in). Measure from hitch
receiver to center of ball.
1. If trailer dimensions are out of range, this feature will be unavailable.
2. Ensure rear trailer camera is connected. 3. Follow instructions to drive forward to
complete calibration.
Rear Trailer Guidance Setup (if equipped)
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 0266.
Trailer dimensions must be in range to
enable this feature.
.Trailer Length: 300 cm (118.1 in) –970 cm
(381.8 in). Measure from center of coupler
to furthest rear point on the trailer.
1. If trailer dimensions are out of range, this feature will be unavailable.
2. Ensure rear trailer camera is connected.
3. Follow instructions to drive forward to complete calibration.
Jack-Knife Alert Setup (if equipped)
Follow instructions to drive forward to
complete calibration.
Trailer Length Indicator Setup (if
equipped)
Follow instructions to drive forward to
complete calibration.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
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Driving and Operating 311
Trailer Side Blind Zone Alert Setup (if
equipped)
Trailer dimensions must be in range to
enable this feature.
.Trailer Length: 300 cm (118.1 in)–
1200 cm (472.4 in). Measure from center
of coupler to furthest rear point on the
trailer.
If trailer dimensions are out of range, this
feature will be unavailable.
Status View
The Status view shows:
.Vehicle
.Connections
.Tires
.Maintenance
.Cameras
Upon entry, the most recent items will be
shown. Select MORE to view all options.
Vehicle
1. Transmission Fluid Temperature
2. Average Fuel Economy with Trailer Profile
Transmission Temperature
View the temperature of the transmission
fluid by looking at the graphic. The graphic
will indicate a dangerous level if the
temperature is at 130 °C–150 °C
(270 °F–300 °F).
Average Fuel Economy
Touch to view the average fuel economy of
the vehicle while the Trailer Profile is active.
Connections
1. Light Test Start Button
2. Trailer Electrical Diagnostics
Connections: OK
If a trailer connection is detected, the view
will display OK.
Trailer Connections Status
When a trailer is connected, the Trailering
App System detects the trailer connection
using the Park and Stop/Turn Signal lighting
circuits and alerts the driver by requesting a
trailer profile setup through the Trailering
App System on the infotainment screen. The
Trailer Detection Alert setting must be
enabled for the alert to display when a