2023 GMC SIERRA warning

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
Driving and Operating 271
When parking your vehicle and your trailer
on a hill:1. Press and hold the brake pedal, but do not shift into P (Park). Turn the wheels
toward 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
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 trailer wiring before backing
the trailer into the water to prevent damage
to the electrical circuits. 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 or Automatic
Four-Wheel Drive.
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.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
Driving and Operating 273
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 must be below all of the
maximum weight ratings for the vehicle,
including:
.Gross Combined Weight Rating (GCWR)
.Gross Vehicle Weight Rating (GVWR)
.Maximum Trailer Weight Rating
.Gross Axle Weight Rating-Rear (GAWR-RR)
.Maximum Trailer Tongue Weight Rating
See “Weight-Distributing Hitch and
Adjustment” underTowing Equipment 0276
to determine if equalizer bars are required
to obtain the maximum trailer weight
rating. See
“Trailer Brakes” underTowing
Equipment 0276 to determine if brakes are
required based on the trailer 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 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
276 Driving and Operating
Towing Equipment
Hitches
{Warning
In order to avoid serious injury or
property damage, always follow the hitch
manufacturer's instructions when securing
your draw bar/coupling device to the
vehicle's hitch receiver.
Ensure that the draw bar/coupling device
is secured with a locking retainer pin or
other means such that rotation of the pin
or locking mechanism will not cause the
pin to back out or loosen during use.
Failure to correctly secure the draw bar/
coupling device to the receiver can result
in separation of the hitch/receiver while
towing.
Conventional Hitch
A conventional hitch is bolted to the frame
or cross member of the tow vehicle, and is
generally rated Class 2, 3, 4, or 5. Gooseneck Hitch
A gooseneck hitch is designed to be coupled
to a special hitch leveraging a hitch ball, and
is mounted over the rear axle in the
truck bed.
Fifth-Wheel Hitch
A fifth-wheel hitch is mounted over the rear
axle in the truck bed, and leverages a
hinged plate
—the same type of hitch
leveraged by semi trucks. Generally,
fifth-wheel hitches accommodate large
trailers with as many as one, two, or three
axles.
Always use the correct hitch equipment for
your vehicle. Crosswinds, large trucks going
by, and rough roads can affect the trailer
and the hitch.
Proper hitch equipment for your vehicle
helps maintain control of the vehicle-trailer
combination. Many trailers can be towed
using a weight-carrying hitch which has a
coupler latched to the hitch ball, or a tow
eye latched to a pintle hook. Other trailers
may require a weight-distributing hitch that
uses spring bars to distribute the trailer
tongue weight between your vehicle and trailer axles. Fifth-wheel and gooseneck
hitches may also be used. See
“Maximum
Trailer Tongue Weight” underTrailer Towing
0 272 for weight limits with various hitch
types.
Avoid sharp turns when using a step-bumper
hitch to prevent damage. Make wider turns
to prevent contact between your trailer and
your bumper.
Consider using mechanical sway controls
with any trailer. Ask a trailering professional
about sway controls or refer to the trailer
manufacturer's recommendations and
instructions.
Weight-Distributing Hitch and
Adjustment
A weight-distributing hitch may be useful
with some trailers. Use the following
guidelines to determine if a
weight-distributing hitch should be used.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
282 Driving and Operating
Turn Signals When Towing a Trailer
When properly connected, the trailer turn
signals will illuminate to indicate the vehicle
is turning, changing lanes, or stopping.
When towing a trailer, the arrows on the
instrument cluster will illuminate even if the
trailer is not properly connected or the bulbs
are burned out.
Tow/Haul Mode
For instructions on how to enter Tow/Haul
Mode, seeDriver Mode Control 0243.
Tow/Haul assists when pulling a heavy
trailer or a large or heavy load. See Tow/
Haul Mode 0234.
Tow/Haul Mode is designed to be most
effective when the vehicle and trailer
combined weight is at least 75% of the
vehicle's Gross Combined Weight Rating
(GCWR). See “Trailer Weight” underTrailer
Towing 0272.
Tow/Haul Mode is most useful when towing
a heavy trailer or carrying a large or
heavy load:
.Through rolling terrain.
.In stop-and-go traffic.
.In busy parking lots. Operating the vehicle in Tow/Haul Mode
when lightly loaded or not towing will not
cause damage; however, it is not
recommended and may result in unpleasant
engine and transmission driving
characteristics, heavy or light steering
efforts, and reduced fuel economy.
Integrated Trailer Brake Control System
The vehicle may have an Integrated Trailer
Brake Control (ITBC) system for use with
electric trailer brakes or most electric over
hydraulic trailer brake systems. These
instructions apply to both types of electric
trailer brakes.
This symbol is on the Trailer Brake Control
Panel on vehicles with an ITBC system. The
power output to the trailer brakes is
proportional to the amount of vehicle
braking. This available power output to the
trailer brakes can be adjusted to a wide
range of trailering situations.
The ITBC system is integrated with the
vehicle’s brake, antilock brake, and
StabiliTrak/Electronic Stability Control (ESC)
systems. In trailering conditions that cause
the vehicle’s antilock brake or StabiliTrak/
ESC systems to activate, power sent to the
trailer's brakes will be automatically
adjusted to minimize trailer wheel lock-up.
This does not imply that the trailer has
StabiliTrak/ESC.
If the vehicle’s brake, antilock brake,
or StabiliTrak/ESC systems are not
functioning properly, the ITBC system may
not function fully or at all. Make sure all of
these systems are fully operational to allow
the ITBC system to function properly.
The ITBC system is powered through the
vehicle's electrical system. Turning the
ignition off will also turn off the ITBC
system. The ITBC system is fully functional
only when the ignition is in on.{Warning
Connecting a trailer that has an air brake
system may result in reduced or
complete loss of trailer braking, including
increased stopping distance or trailer
instability which could result in serious
(Continued)

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
Driving and Operating 283
Warning (Continued)
injury, death, or property damage. Only
use the ITBC system with electric or
electric over hydraulic trailer brake
systems.
Trailer Brake Control Panel
1. Manual Trailer Brake Apply Lever
2. Trailer Symbol
3. Trailer Gain Adjustment Buttons
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. See
Instrument Panel Overview 05.
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.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
284 Driving and Operating
Manual Trailer Brake Apply Lever
Slide this lever 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.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 BRAKES 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 vehicle is turned off. This
message will also turn off if it is
acknowledged or if the trailer harness is
reconnected.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
Driving and Operating 285
.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 vehicle off.
3. Wait 10 seconds, then turn the vehicle 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.
TRAILER BRAKES DISABLED SERVICE
REQUIRED: This message will display when
there is a problem with the ITBC system.
If this message continues over multiple
restarts, have the vehicle serviced. If either the CHECK TRAILER WIRING, TRAILER
BRAKES DISABLED SERVICE REQUIRED,
SERVICE TRAILER BRAKES, HOLD LAST KNOWN
GAIN, or REDUCED TRAILER BRAKING
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 vehicle off.
Check the wiring connection to the trailer
and turn the vehicle back on. If either of
these messages continue, 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 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 slow the vehicle. TSC will not
function if StabiliTrak/ESC is turned off. See
Traction Control/Electronic Stability Control
0
241.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
286 Driving and Operating
{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 Equipment0276 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 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.