2023 GMC SIERRA parking brake

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260 Driving and Operating
Warning (Continued)
.Detect a vehicle ahead if it is partially
blocked by pedestrians or other
objects.
Complete attention is always required
while driving, and you should be ready to
take action and apply the brakes and/or
steer the vehicle to avoid crashes.
AEB may slow the vehicle to a complete
stop to try to avoid a potential crash. If this
happens, AEB may engage the Electric
Parking Brake (EPB) to hold the vehicle at a
stop. Release the EPB or firmly press the
accelerator pedal.
{Warning
AEB may automatically brake the vehicle
suddenly in situations where it is
unexpected and undesired. It could
respond to a turning vehicle ahead,
guardrails, signs, and other non-moving
objects. To override AEB, firmly press the
accelerator pedal, if it is safe to do so.
Intelligent Brake Assist (IBA)
IBA may activate when the brake pedal is
applied quickly by providing a boost to
braking based on the speed of approach and
distance to a vehicle ahead.
Minor brake pedal pulsations or pedal
movement during this time is normal and
the brake pedal should continue to be
applied as needed. IBA will automatically
disengage only when the brake pedal is
released.
{Warning
IBA may increase vehicle braking in
situations when it may not be necessary.
You could block the flow of traffic. If this
occurs, take your foot off the brake pedal
and then apply the brakes as needed.
AEB and IBA can be disabled. To view
available settings for this feature, touch the
Settings icon on the infotainment home
page. Select “Vehicle”to display the list of
available options and select “Collision/
Detection Systems”.
{Warning
Using AEB or IBA while towing a trailer
could cause you to lose control of the
vehicle and crash. Turn the system to
Alert or Off when towing a trailer.
A system unavailable message may
display if:
.The front of the vehicle or windshield is
not clean.
.Heavy rain or snow is interfering with
object detection.
.There is a problem with the StabiliTrak/
Electronic Stability Control (ESC) system.
The AEB system does not need service.
Side Blind Zone Alert (SBZA)
If equipped, the SBZA system is a
lane-changing aid that assists drivers with
avoiding crashes that occur with moving
vehicles in the side blind zone, or blind spot
areas. When the vehicle is in a forward gear,
the left or right side mirror display will light
up if a moving vehicle is detected in that
blind zone. If the turn signal is activated and
a vehicle is also detected on the same side,
the display will flash as an extra warning
not to change lanes. Since this system is

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
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Driving and Operating 269
.Become familiar with, and follow all state
and local laws that apply to trailer
towing. These requirements vary from
state to state.
.State laws may require the use of
extended side view mirrors. If your
visibility is limited or restricted while
towing, install extended side view mirrors
on your vehicle, even if not required.
.Do not tow a trailer during the first
800 km (500 mi) of vehicle use to prevent
damage to the engine, axle, or other
parts.
.Perform the first oil change before heavy
towing.
.Do not drive over 800 km/h (50 mph) and
do not make starts at full throttle during
the first 800 km (500 mi) of trailer
towing.
.Tow in D (Drive). Tow/Haul Mode is
recommended for heavier trailers. See
Tow/Haul Mode0234. If the transmission
downshifts too often, a lower gear may
be selected using Manual Mode. See
Manual Mode 0232.
If equipped, the following driver assistance
features should be turned off when towing
a trailer:
.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, unless equipped with
Super Cruise:
.Automatic Emergency Braking (AEB)
.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: (Continued)
Warning (Continued)
.Do not drive with the liftgate, trunk/
hatch, or rear-most window open.
.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 0229.
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 unexpected or unsafe manner.
Before driving, inspect all trailer hitch parts
and attachments, safety chains, electrical
connectors, lamps, tires, and mirrors. See
Towing Equipment 0276. If the trailer has
electric brakes, start the combination

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
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270 Driving and Operating
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 TurnsCaution
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. 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
Overheating 0313.
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 0246.
Parking on Hills
{Warning
To prevent serious injury or death,
always park your vehicle and trailer on a
level surface when possible.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
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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-
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272 Driving and Operating
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 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
Schedule 0385. 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 0313.
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, and
durability. 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.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
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Driving and Operating 279
to the attaching points on the bumper;
otherwise, safety chains should be attached
to holes on the trailer hitch.
Cross the safety chains under the tongue of
the trailer to help prevent the tongue from
contacting the road if it becomes separated
from the hitch. Always leave enough slack in
the safety chains to allow the combination
to turn. Never allow safety chains to drag
on the ground.
Trailer Brakes
Loaded trailers over 900 kg (2,000 lb) must
be equipped with brake systems and with
brakes for each axle. Trailer braking
equipment conforming to Canadian
Standards Association (CSA) requirement
CAN3-D313, or its equivalent, is
recommended.
State or local regulations may require
trailers to have their own braking system if
the loaded weight of the trailer exceeds
certain minimums that can vary from state
to state. Read and follow the instructions for
the trailer brakes so they are installed,
adjusted, and maintained properly. Never
attempt to tap into your vehicle's hydraulicbrake system. If you do, both the vehicle
antilock brakes and the trailer brakes may
not function, which could result in a crash.
Auxiliary Battery
If equipped, the vehicle's auxiliary battery
can be used to supply electrical power to
additional equipment that may be added,
such as a slide-in camper.
Locate the auxiliary battery connector under
the hood on the driver side of the vehicle,
next to the engine compartment fuse block.
Follow the proper installation instructions
included with any electrical equipment that
is installed.
Caution
To prevent draining the auxiliary battery,
always turn off electrical equipment
when not in use and do not use any
equipment that may exceed the
maximum amperage rating of 30 amps.
Trailer Wiring Harness
Basic Trailer Wiring
If the vehicle is not equipped with a trailer
connector on the rear bumper, a 7-wire
trailering harness is tied to the vehiclesframe. The harness requires the installation
of a trailer connector, which is available
through your dealer.
Use only a round, seven-wire connector with
flat blade terminals meeting SAE J2863
specifications for proper electrical
connectivity.
The seven-wire harness contains the
following trailer circuits:
Stop/Turn
Signal Left Yellow/Blue
Stop/Turn Signal
Right Green/Violet
Tail/Parking Lamps Gray/Brown
Reverse Lamps White/Green
Battery Feed Red/Green
Ground White
Electric Trailer Brake Blue
Heavy-Duty Trailer Wiring Harness Package
If equipped, the trailer wiring harness, with
a seven-pin connector and a four-pin
connector, is mounted on the vehicle's rear
bumper.

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Driving and Operating 281
Camper/Fifth-Wheel Trailer Wiring Package
For vehicles without the fifth-wheel/
gooseneck trailer package, the seven-wire
camper harness is under the rear bumper,
attached to the frame near the rear
crossmember. A connector must be added to
the wiring harness that connects to the
camper.
The harness contains the following
camper/trailer circuits:Stop/Turn
Signal Left Yellow/Blue
Stop/Turn Signal
Right Green/Violet
Tail/Parking Lamps Gray/Brown Reverse Lamps White/Green
Battery Feed Red/Green
Ground White
Electric Trailer Brake Blue
If equipped with the heavy-duty trailering
option, see “Heavy-Duty Trailer Wiring
Harness Package” earlier in this section.
When the camper-wiring harness is ordered
without the heavy-duty trailering package, a
seven-wire harness with a seven-pin
connector is at the rear of the vehicle and is
tied to the vehicle's frame.
Trailer Lamps
Always check that all trailer lamps are
working at the beginning of each trip, and
periodically on longer trips.
If equipped, the Trailering App will monitor
the RH turn/brake lamp circuit, LH turn/
brake lamp circuit, running lamp circuit, and
reverse lamp circuits on the trailer. Driver
Information Center (DIC) messages and
Trailering App alerts may display if lighting
circuit issues are detected on the trailer. When a trailer cannot be detected, the
trailer-related DIC messages and/or
Trailering App alerts will not display.
Pressing START LIGHT TEST in the Trailering
App automatically activates trailer lamps.
The Trailering App is not a substitute for
manually inspecting your trailer lamps. See
Trailering App
0287.
Trailer Connection and Lamp Messages
When a trailer is properly connected and
working, no trailer connection or lamp
messages appear on the Driver Information
Center (DIC). However; if the vehicle detects
an issue with a trailer connection or lamp,
you may see the following DIC message(s):
.TRAILER DISCONNECTED CHECK
CONNECTION appears when a connected
trailer is disconnected. It appears
immediately when the vehicle is on,
or upon the next start-up if the trailer
was disconnected while the vehicle was
off. Check the trailer connection as
appropriate.
.CHECK TRAILER LAMP appears when there
is a detected lamp or wiring fault on the
trailer. Check the trailer wiring and lamps.

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)